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5 | How competitive is your salary?
Salary and bonuses earned show mechanical engineers made the most money
BUILDING SOLUTIONS
6 | Considerations for emergency generator systems
Learn about factors to consider when designing a generator for emergency power
12 | Power for emergency systems focus on value add
Value-add strategies intend to help owners build better business cases
16 | Existing generators: Extending service life strategies and reuse case studies
Due to long lead times, maintaining or relocating existing generators is a possible solution
22 | Case study: Electrical room design for hospital campuses
A hospital in the Southeast had several electrical infrastructure design considerations
JANUARY/FEBRUARY 2023
NEWS &BUSINESS BUILDING SOLUTIONS
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54 | Offices change, accommodating new work styles
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RAYMOND GRILL, PE, FSFPE, LEED AP, Principal, Ray Grill Consulting, PLLC, Clifton, Va.
DANNA JENSEN, PE, LEED AP BD+C, Principal, Certus, Carrollton, Texas
WILLIAM KOFFEL, PE, FSFPE, President, Koffel Associates Inc., Columbia, Md.
WILLIAM KOSIK, PE, CEM, LEED AP BD+C, BEMP, Senior Energy Engineer, Oak Park Ill.
KENNETH KUTSMEDA, PE, LEED AP, Engineering Manager, Jacobs, Philadelphia
JULIANNE LAUE, PE, LEED AP BD+C, BEMP, Director of Building Performance, Mortenson, Minneapolis
DAVID LOWREY, Chief Fire Marshal, Boulder (Colo.) Fire Rescue
JASON MAJERUS, PE, CEM, LEED AP, Principal, DLR Group, Cleveland
BRIAN MARTIN, PE, Senior Electrical Technologist, Jacobs, Portland, Ore.
BEN OLEJNICZAK, PE, Senior Project Engineer, Mechanical, ESD, Chicago
GREGORY QUINN, PE, NCEES, LEED AP, Principal, Health Care Market Leader, Affiliated Engineers Inc., Madison, Wis.
BRIAN A. RENER, PE, LEED AP, Principal, Electrical Discipline Leader, SmithGroup, Chicago
SUNONDO ROY, PE, LEED AP, Director, Design Group, Romeoville, Ill.
JONATHAN SAJDAK, PE, Senior Associate/Fire Protection Engineer, Page, Houston
RANDY SCHRECENGOST, PE, CEM, Austin Operations Group Manager/Senior Mechanical Engineer, Stanley Consultants, Austin, Texas
MATT SHORT, PE, Project Manager/Mechanical Engineer, Smith Seckman Reid, Houston
MARIO VECCHIARELLO, PE, CEM, GBE, Senior Vice President, CDM Smith Inc., Boston
RICHARD VEDVIK, PE, Senior Electrical Engineer and Acoustics Engineer, IMEG Corp., Rock Island, Ill.
TOBY WHITE, PE, LEED AP, Associate, Boston Fire & Life Safety Leader, Arup, Boston
APRIL WOODS, PE, LEED AP BD+C, Vice President, WSP USA, Orlando, Fla.
JOHN YOON, PE, LEED AP ID+C, Lead Electrical Engineer, McGuire Engineers Inc., Chicago
How competitive is your salary?
Salary and bonuses earned show mechanical engineers made the most money
Alot of architectural engineering firms are growing and have been growing quite a bit for a couple of years. COVID19 necessitated that a lot of firms reconfigure engineered systems or even whole buildings, offering many unexpected projects. The long hours, the creative solutions and the inability to complete certain jobs then lead to a backlog.
tics aren’t your thing, at least know what others in similar positions are making.
In the annual Consulting-Specifying Engineer salary survey, we have gathered this data for you. Here are a few engineering salary survey insights:
Amara Rozgus, Editor-in-Chief
Some firms have projected their growth, through mergers, acquisitions or business development in specific markets. Using models to predict the future helps engineering firms figure out where they are, and where they eventually want to be.
The wildcard in every firm’s growth is its people. What happens when a leader leaves? How do you hire enough entry-level folks? How do you keep that mid-level manager happy in his job slump?
Money isn’t everything, though it does say a lot. A competitive salary and eventual raises points to management support, and believing in the knowledge and abilities of its staff. It also keeps an employee satisfied, and happy they work for a forward-thinking company.
On the flipside, it’s important for a consulting engineer to know what he’s worth. Salary, bonuses, benefits and other company perks all play into the equation. If negotiating tac-
• The average engineering professional is 51 years old, plans to retire in 2038, and worked on approximately 33 total projects last year.
• The average engineering professional earned a base salary of about $112,600 in 2021, a 3.2% increase over 2020 data. Nearly seven out of 10 respondents reported an increase in total compensation between 2020 and 2021.
• Three-quarters of engineers received a form of nonsalary compensation in 2021 (e.g., bonus, profit sharing, stock shares); the average amount awarded was about $13,000.
This year, mechanical engineers who work on HVAC and plumbing systems came out on top at $129,829 for total compensation. And, not surprisingly, engineers with a “senior administration” job title or role made the most: $136,348.
To help determine whether you and your company are prepared for the future, download the full study to compare yourself against your peers. cse
Bianca Jimenez, PE; and Rick Baca, SmithGroup, Phoenix
Considerations for emergency generator systems
Learn about factors to consider when designing a generator for an emergency power system
When designing a new facility, one of the first space planning questions by the design team is, “Do we need a generator?” For the engineer, the answer can be obvious — or the project application may be complex and require a code study to determine the need and system configuration.
There are standard building systems that often require defined operational time during a normal power outage, such as egress lighting, but often a designer will plan for a generator if longer runtimes are required or if there are larger operational loads. If a battery cannot support the code requirement, the engineer will look at generators as the next option.
Examples of emergency generator systems applications are fire pumps, high-rise buildings, atriums, chemical exhaust systems and hospitals. Less common examples can include critical operations power systems facilities or high-density storage facilities.
While egress lighting and other life safety systems could be served with a central or distributed battery system, a generator becomes a practical application when other legally required and optional standby loads are introduced into the generator system, as these tend to be considerable electrical loads. In some cases, even when a central battery system or distributed batteries would suffice, the client will find a generator more practical to maintain.
Engineering design has a priority obligation to public safety and the liability risk is there to reinforce professional ethics. The National Society of Professional Engineers state as its first canon that “Engineers, in the fulfillment of their professional duties, shall: 1. Hold paramount the safety, health and welfare of the public.” The engineering review of emergency systems is essential for every project and should be taken seriously.
FIGURE 1: Perspective rendering of utility yard including generator, nedium-voltage transformer and medium-voltage switch, located behind an architectural screen wall, emphasizing the visual cohesion between the utility space and the building exterior, at the Applied Research Building in Tucson, Arizona. Courtesy: Ryan Haines, SmithGroup
Objectives Learningu
• Understand the physical components of an emergency power system.
• Become familiar with interdisciplinary design factors and physical considerations of emergency power systems.
• Learn key talking points for a better-integrated design for emergency power systems.
When codes and standards require generators
Some projects do not require a generator distribution system per code, but are required by the client for operational purposes. Other projects may want to combine standby power systems with the emergency power system, which is allowed if there is a proper load shedding schemes provided. There may also be facilities where medium-voltage generators greater than 600 volts become practical. While often overlapping in architectural considerations, this article will not discuss those unique details.
All devices and control devices in the emergency system must be tested and listed by an agency approved by the authority having jurisdiction for their intended use. There are many different types of listings for testing. UL Solutions’ 2200 is required for stationary engine generators. UL 1008 is required for transfer switch equipment. UL 924 is required for emergency lighting automatic load control relays.
It is also essential to understand that only some devices are intended for emergency operations. Light fixtures, for example, can be used for egress, but only certain portions of the facility lighting systems are designed for use as an egress system. The egress lighting system can be provided with 90-minute battery backup or supplied from an emergency generator system.
EPSS. EPS is “the source of electric power of the required capacity and quality for an emergency power supply system,” which is often the generator itself. EPSS is ‘’a complete functioning system … needed for the system to operate.”
A typical system will consist of the generator(s), transfer switches, load banks, temporary generator connections, distribution boards, panelboards, breakers and all the pathways in between. This will apply to all systems requiring emergency support, such as egress lighting, emergency exhaust or critical heating, ventilation and air conditioning.
‘ Engineering design has a priority obligation to public safety and the liability risk is there to reinforce professional ethics.’
Where do we put a generator?
For example, power packs are listed for normal and UL 924 operation. Misapplying and/or missing the listing and testing requirements can be a considerable complication resulting in cascading implications.
What is in an emergency system?
NFPA 110: Standard for Emergency and Standby Power Systems includes two important definitions for emergency systems, emergency power supply, or EPS, and emergency power supply system, or
The generator and emergency systems can physically reside in the building’s interior, exterior, above grade or even on the roof — and likely a combination of locations if access is limited to qualified persons. Subgrade installation is a possibility but usually avoided due to the potential of water intrusion during a flood scenario. Several factors will determine location, including engineering judgment, code requirements and project parameters, to “minimize the probability of equipment or cable failure” (NFPA 110 7.1.1).
When installed within building interior spaces, EPS units must be in a separate room with a twohour rating with exclusively EPSS equipment per NFPA 110 7.2.1. Also, consider that if the genera-
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Generator insights
u Commercial buildings often use generators to provide power for backup, emergency or life safety.
u Specifying a generator requires the engineer to ask several questions and to consider the siting of the genset.
FIGURE 2: This shows the interior generator installation for a hospital facility located in Phoenix, Arizona. Courtesy SmithGroup
BUILDING SOLUTIONS UILDING
tor is interior to the building, the motor will likely cause vibrations that some facilities may not tolerate.
When installed outdoors, weather-rated enclosures maintain the functionality of the EPS and are a viable solution, provided the enclosure is rated to resist the ingress of weather to the level required by the local building codes. Appropriate weather-rated housings and a single enclosure often simplify the design for operations and points of risks. The noise attenuation of the outdoor enclosure is also a consideration.
While the electrical engineer may find the generator aesthetically pleasing and worthy of showcasing, there are applications where a generator should be inconspicuously located, either for architectural design or facility/operational considerations. This is important for certain government projects and other sensitive facilities where the generator provides redundancy and resiliency for people or critical systems. An obvious and easily accessible generator can make for a high-value target. As an integrated product, the generator can be incorporated into the visual parameters of the project while providing a level of security when required.
While the electrical rooms can be placed as needed for the architectural program, it is more efficient, constructible, cost-effective and manageable if the interior and exterior equipment are adjacent. Ideally, the generator feeders should be in a direct route to the distribution board. This becomes more critical where there are paralleled generators. A clear and direct route is beneficial because the underground organization can become complicated with adjacent wet and dry systems. A simplified route also has the benefit of reducing the length and, therefore, cost. The actual maintenance, observations and testing become simplified when the generator is adjacent to the space with the transfer switches due to accessibility.
While the generator and distribution system are in areas accessible to only qualified personnel, the associated remote annunciation devices are strategically placed at normally staffed locations to alert them of system status and operational issues.
If the generator is near the building service transformer, required clearances should be reviewed with the AHJ, owner and utility requirements. As well as potential insurance requirements such as FM Global. It is often recommended that an emergency generator be provided with a fire-rated wall in case of fire at either source, or provided the recommended clear distance.
It is also important to consider the practical elements of planning a generator yard. There should be adequate lighting so the generator can be maintained during an outage. That could mean circuiting lighting, access doors and receptacles to a life safety circuit. It is a great benefit to the project or building to have an early run-through of major building components and potential outage procedures with building facilities personnel during design.
Furthermore, with climate change becoming an increasing issue in electrical systems resiliency, the floodplain is not an item that can be ignored. Great care should be used with locating the emergency systems. Consider if the equipment is in a 100year or even 200-year flood plain. Is the equipment located in an area with hurricanes and tornadoes? These resiliency considerations will guide the configurational basis of the system.
If the EPS (generator) is located outdoors and Level 1 EPSS equipment is located indoors, the system must have a room separate from the normal
FIGURE 3: A generator appears in a chiller yard with a utility transformer in the distance, located in Texas. Courtesy: Wade Griffith, SmithGroup
service per NFPA 110 7.2.3. When the EPS is located indoors, the room per NFPA 110 7.2.1, must have a two-hour fire rating.
It is often recommended that the EPSS room also has a two-hour fire rating because of the 90-minute operating time required for the egress system or protection requirements for specific types of emergency support systems. Regularly a combination of interior and exterior locations are utilized, but in all scenarios planning to mitigate risk in all forms is critical for an optimal installation.
The NFPA 70: National Electrical Code restricts the height of the disconnecting means to 6 feet, 7 inches per NEC 2017 240.24(A) to allow access with the ability to use “portable equipment” when the “overcurrent device is adjacent to the utilization equipment.” Depending on the AHJ, there can be various interpretations.
There are various ways to meet this requirement and the recommended method should be reviewed and approved during design. It could be that a readily accessible ladder or strategically located emergency power off switch meets the intent or a permanent perimeter platform must be installed.
Generator ventilation
It is tempting to provide the minimum clearances around the generator for maintenance, but it is also important to allow enough breathing room for intake and discharge ventilation. While it has always been good practice to provide enough space to walk around the enclosure doors, NFPA 1102022 codified the clearance requirements in section 7.2.6.1 that generators are to be provided with “36 inches of working space access for inspection, repair, maintenance, cleaning or replacement from the outside edge of the enclosure or sufficient space to fully open all hinged doors, whichever is greater.”
The ventilation needs can vary by manufacturer and accessories. Ventilation is critical in an environment with high heat, such as the desert, so the hot ambient air does not recirculate the already increasing hot air into the generator and overheat the engine. For exterior units, there are accessory options such as low intake or vertical-discharge hoods that help manage the recirculation and could also tighten the space needed, but the dimensions should be confirmed before reducing the expected generator area.
‘ With climate change becoming an increasing issue in electrical systems resiliency, the floodplain is not an item that can be ignored. ’
NFPA 110 7.7.1 calls for provisions “to limit the maximum air temperature in the EPS room or the enclosure housing the unit to the maximum ambient air temperature required by the EPS manufacturer.” An interior EPS room will require intake, discharge and ventilation directly from the exterior through a wall ‘’or a two-hour fire-rated air transfer system” per NFPA 110 7.7.2.
Fuel requirements for generators
There is a common misconception that the larger the generator, the longer the runtime, which is inaccurate. Generators are sized to accommodate the required loads, but the fuel tank capacity determines the actual runtime. NFPA 110 5.5.3 indicates that the tank shall “support the duration of the run specified,” and NFPA 110 7.9 further clarifies that the “fuel tanks shall be sized to accommodate the specific EPS class.”
The generator kilowatt rating and fuel are required to prioritize adequate capacity to Level 1 and Level 2 loads, then optional loads per NFPA 110 7.1.5. The potential runtime consumption rate of the generator varies by manufacturer, but the operational full load of gallons per hour can be requested.
When considering “the generator cannot ever go down” project parameter, the answer isn’t always to add more fuel. Fuel must be cleaned and maintained — commonly referred to as polishing and the system must also have the varnish periodically removed. Factors such as representative service in the area, distance from the nearest fuel supplier or availability of fuel in the area need to be considered.
A conversation regarding the client’s experience in the area can clarify the specific requirements to bring balance to performance and value. NFPA 110 7.9.1.3 clarifies that “tanks shall be sized so
BUILDING SOLUTIONS UILDING
FIGURE 4:
Generator with support platform is located at Johnson County’s Medical Examiner Facility. Courtesy: Michael Robinson, SmithGroup
that fuel is consumed within the storage life or provisions shall be made to remediate fuel.”
Fuel tanks have specific requirements in NFPA 30, 37, 54 and 58 that may also call for additional protections contingent on the type of tank. NFPA 37: Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines defines the requirements and maintains that the engines shall be readily accessible for “maintenance, repair and firefighting” (NFPA 37 4.1.1).
NFPA 37-2021 section 4.1.2.1 calls for engine rooms to have “at least one-hour fire-resistance rating” for walls and floors, with the rating maintained for the ceiling unless it is otherwise protected or noncombustible. Section 4.1.4 calls for outdoor generators in “weatherproof housings that are installed outdoors shall be located at least 5 feet from any openings in the walls of structures” or from structures having combustible walls unless complying to the exception of “the structure having a fire-resistance rating of at least one hour” in nonhazardous locations.
There are also exceptions to reduce the 5 feet clearance if fire testing is conducted. Similar requirements apply to engines located on the roof. Regardless of location, containment of fuel in the possibility of a spill or leak should be coordinated with the requirements of the space. It is possible to get a double-walled fuel tank, but containment curbs or pumps should be coordinated if that is not provided.
There is a limit to the amount of fuel that can be placed interior to a building or on the roof. NFPA 110 7.9.5 calls for a maximum quantity of 660 gallons of diesel fuel “inside or on roofs of structures.” Often when there is a need to extend the potential runtime of the tank in these locations. A refueling system and day tank, above or below ground, will be required and will need extra planning and discussion with the AHJ. The fuel port will need to be accessible and secure.
Usually, when a fuel port is required, a recirculation system will also have to be provided to get from the ground level up or across a long distance. Refueling systems are also costly because the fuel lines have separate fire protection requirements for safety. Direct routing and immediate adjacency are the most effective and economical.
Additionally, it is important to plan a path for refueling. Hose lengths can vary depending on the supplier, but the general expectation is to plan for a minimum 25-foot hose, with some suppliers having options for extensions. Many fuel vendors also have a small pump to push or pull the diesel gas an extended distance.
If the generator uses natural gas, it doesn’t mean fuel planning can be ignored. Natural gas piping will need access to the generator pad and can be costly if the natural gas piping is not near the electrical utility yard. Natural gas may not be considered a reliable source in all jurisdictions. It is important to note that natural gas generators have a practical operational limitation or rating, for EPSS.
Testing and maintenance
Generators produce considerable sound. It is important to consider the generator’s location for internal occupants and exterior adjacencies. AHJs have sound ordinances and if located adjacent to any residential neighborhoods; these ordinances can be very strict. Sound is measured in decibels and is a condition of distance. When coordinating the decibel level, a clear understanding of the surrounding environment is essential.
The code requires periodic testing for emergency systems. General requirements of NFPA 110 8.4.1 call for documented ESS testing at least monthly for at least 30 minutes. Periodic testing mitigates the likelihood of a failure during a normal power outage. It is important as a team to commu-
nicate that emergency systems will operate based on how well they are maintained.
Additionally, the generator breaker is a part of the coordination, short circuit and arc flash studies. These studies are code required for emergency systems and often require physical confirmation of the configuration. It is important to plan the time and coordination between suppliers for this to occur during the submittal review and before project closeout.
The 2017 edition of the NEC 700.3 (F) requires equipment provisions for a straightforward connection of a temporary power source in the event the permanent generator is out of service due to failure or maintenance. It is important to consider where the temporary generator could be located. The cables connecting to the equipment provisions, often a plug-style or triple switch-like configuration, aren’t intended to be in driveways or will require additional protection.
The optimal planned location for a temporary power source is adjacent to the switching means. Planning the parking area for the temporary gener-
‘ Natural gas piping will need access to the generator pad and can be costly if the natural gas piping is not near the electrical utility yard. ’
ator connection can save the operator time during the outage, often saving costs and increasing safety.
Ultimately, the emergency systems cannot be designed in isolation and successful system design will be the product of integrated communication between the AHJ, stakeholders, disciplines and clients. cse
Bianca Jimenez,PE, is a senior electrical engineer at SmithGroup. She has more than 10 years of experience currently focusing on science and technology projects.
Rick Baca is a senior electrical designer at SmithGroup. He has more than 19 years of experience in electrical engineering with a focus in health care.
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Simon Gandica, PE, PMP, Smith Seckman Reid Inc., Houston
Power for emergency systems focus on value add
Value-add strategies intend to help owners build better business cases to install and operate larger generation capacity that can mitigate major environmental events that create extended power outages
Power for emergency systems is a broad and complex topic. There are many articles explaining the technical aspects of power for emergency systems, as well as listing code requirements justifying the way emergency systems are designed. This article takes a slightly different approach and presents how power for emergency systems also can be designed to add financial value the owner's operation.
ed to add value to the business should also keep the safety of the operation in the facility as the main priority.
Learningu
Objectives
• Gain an understanding of how a facility’s power generation can reduce demand on a local utility and contribute to a facility’s bottom line.
• Look at an overview of the pros and cons of a demand response program.
• Review the concept of peak shaving to limit peak demand.
Most building systems are capital expenditures. The building core, shell, finishes, electrical, plumbing and heating, ventilation and air conditioning systems in general cost money to the owner without any tangible return on investment. Capital expenditures are typically capitalized and become fixed assets that are depreciated overtime. This is also true for power generators; however, power generators are unique because owners can take advantage of local generation, used to primarily power emergency systems, to negotiate low energy rates and offset electrical utility charges.
Power generation for emergency systems
The financial gains resulting from generating local electricity with nonrenewable sources cannot be realized as income unless the owner is a utility provider; but the value added by local generation is tangible and positively impacts the owner's bottom line. Power generator systems can also be designed to provide reliable power to high revenue areas of buildings. All design decisions orient-
NFPA 70: National Electrical Code defines emergency systems as "those systems legally required and classed as emergency by municipal, state, federal or other codes or by any governmental agency having jurisdiction." An emergency power supply provides power for emergency systems and is defined as "the source of electrical power of the required capacity and qualify for an emergency power supply system."
In other words, an EPS is an alternate source of power, typically local to the facility that provides power to specific loads necessary to safely operate a facility and to allow occupants to exit the building in a safe manner during emergency situations. Emergency power can come from a variety of sources. Power generators, either diesel or natural gas, are the most common sources of emergency power although energy storage units are also popular in the form of batteries, inverters and UPSs.
Added value strategies for emergency power
The most commonly added value strategy to negotiate low energy rates and offset electrical utility charges is to take advantage of utility companies' demand response programs. According to the Electric Power Research Institute, there are many power generators already integrated within customers' power systems that do not operate when utility power is available. At the same time, EPRI explained that 33 out of 40 of the largest power
companies in the U.S. offer incentives for customers that make their generators available to support the utility grid; some of those programs have been in place since the 1970s.
Utility companies create these programs to be able to mitigate generation and distribution constraints. Thus, there are attractive financial incentive for generator owners to make those units available on demand. The Florida Power and Light refers to its program as commercial demand reduction and explains that its intent is to reduce the system peak demand during capacity shortfalls or system emergencies. FPL advertises substantial reduction in electric bills. Owners participating in the program take advantage of the rate discounts year-round, yet their local power generator capacity was only available when hurricane Ian affected Florida’s west coast in September 2022.
From the customer standpoint, demand response programs are written around voluntary load curtailment. Those programs put in place terms and conditions that define the maximum frequency and duration of events. Commonwealth Edison Co. specifies in its contracts a maximum curtailment frequency of 20 events and 100 total hours per year. Customers remain connected to the grid, thus if the local generation fails, power from the grid remains available for the customer to use.
The magnitude of the financial benefits for customers depends on how much load customers are willing to shave off the grid by transferring it to the local generators or simply by shutting down certain building loads. The financial benefit also depends on how much notice the customer agrees to perform the load transfer.
There are different engineering strategies to design new power systems or retrofit existing ones that are flexible enough to take full advantage of demand response programs. These strategies should take into consideration the criticality of the customer's operation, the sophistication of their maintenance staff and the upfront cost that the customer is willing to invest.
One simple way to design a system that can take full advantage of demand response programs is to size the power generation system for full back up, which means that power generators have the capacity to serve the facility under peak demand. By doing so, the customer can agree to curtail 100% of the building load on short notice, which allows power companies to offer the highest incentives.
FIGURE 1: Illustrating power company's interruptible program. Facility is consuming power from the grid. Courtesy: Smith Seckman Reid, Inc.
‘ There are different engineering strategies to design new power systems or retrofit existing ones that are flexible enough to take full advantage of demand response programs.’
Full backup does not mean to substantially upsize the power generators.
Emergency generators are sized to power the highest probable emergency loads of the facility. Most emergency generators run lightly loaded. A properly engineered controls and load shedding scheme allow owners to take full advantage of the available capacity when emergency loads are not operating at peak demand. Thus, the incremental cost of upsizing the generator to provide full back up is off set by the benefit of discounted utility rates.
There are some considerations to make when engineering an emergency power system that is designed for demand response. One of them is to determine who is responsible to perform the load curtailments. Some power companies require the integration of remote terminal units in the customer’s infrastructure; RTUs give control to the power company to start the generators and curtail load. The advantage of this configuration is that power companies maintain trained professionals on staff to perform these operations.
csemag.com
Emergency Systems
u To negotiate low energy rates and offset electrical utility charges, owners can take advantage of local power generation.
u Power generators, either diesel or natural gas, are the most common sources of emergency power.
u To mitigate generation and distribution constraints, utility companies create demand response programs. There are attractive financial incentives for generator owners to make those units available on demand.
BUILDING SOLUTIONS UILDING
FIGURE 2: Facility has switched to local power generators, taking the building off the grid.
Courtesy: Smith Seckman Reid, Inc.
‘ The controls system for peak shaving is commonly integrated within the generators, paralleling gear or automatic transfer switch control scheme. ’
Some customers are highly skeptical to provide third-party companies with control of the backup infrastructure. Demand response contracts can be negotiated for customers to maintain control of the load curtailment. In this case, power companies agree to notify the customer for the need of load curtailment and the customer agrees to shed the load within the agreed upon timeframe.
Not every customer or every power system is suitable for full back up. Power generators can serve the load of the facility partially. Since the power curtailment is monitored at the meter, customers can still benefit from serving their loads partially. Demand response contracts cover a specific amount of power that the customer will drop. This amount is set by the customer and does not need to be the total facility demand. Thus, providing generator power certain areas of the system, or existing systems that already serve emergency loads still create an opportunity for customers to participate in demand response programs.
Whether it is full or partial back up, the terms and conditions if interruptible programs apply only when the power grid is available to the customer. Since the code-required use of emergency generators is limited to power emergency loads when utility power is unavailable, the benefit of making emergency generators for interruptible programs comes from taking advantage of the available infrastructure to create value to the customer when the equipment is not in use.
Should peak demand rely on an emergency system?
Another opportunity to add value with emergency generators is by managing the customer’s peak demand. When analyzing utility bills for large customers, a large portion of the monthly charges is related to demand (kilowatt), not consumption (kilowatt-hour). Consequently, a customer that consumes 500,000 kWh per month pays more if the peak demand is 3,000 kW than a customer that consumes the same kilowatt-hour with a peak demand of 2,000 kW. The billing cycle is divided in intervals. In Texas for instance, CenterPoint Energy breaks the billing cycle in 15-minute intervals; as a result, the highest demand average of any 15-minute interval sets the peak for the billing cycle.
Peak shaving is the strategy that uses power generators to limit peak demand. Similarly, to demand response, demand readings happen at the meter. Therefore, any load transferred to the local generators contributes to lower the peak demand recorded at the utility meter. Peak shaving has some advantages such that any type of load can be transferred to the generators, not necessarily emergency loads, so customers can identify those loads not critical to the day-to-day operations to minimize risk. A separate automatic transfer switch is installed on nonemergency load to prevent a fault on those loads from affecting any emergency load.
Another advantage is the simplicity of the system. The controls system for peak shaving is commonly integrated within the generators, paralleling gear or automatic transfer switch control scheme. Peak shaving happens on the customer side, so there are no contracts to negotiate with utility providers. Ideally, the power system is engineered for peak shaving, but existing systems
can also be retrofitted to take advantage of peak shaving with limited investment. Conversely, the downside of peak shaving is that the customer only acknowledges the financial value if the generators are running. Interruptible programs on the other hand let customers benefit from lower rates even if they are never called to curtail load.
Nonemergency loads
When power generators are sized to serve nonemergency loads, there is an opportunity for customers to identify high revenue areas that would bring substantial financial benefits from staying operational during power outages. The health care sector is a premium example of this. The power system for a health care facility is typically oversized due in part to the codes that regulate the sector. Article 517 of the NFPA 70, for instance, requires the installation of three separate branches for hospitals “capable of supplying a limited amount of lighting and power service that is considered essential for the life and effective hospital operation during the time the normal electrical service is interrupted for any reason.”
To accomplish this, life safety, critical and equipment branches are built from separate transfer switches. Each branch serves a specific group of loads allowed by code; the diversity factors applied to those loads are low, creating the need for large power generators that will be lightly loaded most of the time. Nevertheless, the code allows for the installation of a fourth branch to serve optional loads as long as the transfer won’t overload the generating equipment. These loads shed automatically before the generating equipment is overloaded. Imaging equipment is generally considered an optional load, yet they bring substantial revenue to most hospital operators. Therefore, adding imaging equipment to the optional branch of the hospital creates financial value to the owner of the facility.
Creating more value
Power for emergency systems has expensive installation and operating cost, although they are extremely important to the safe operation of the facility. These value-add strategies intend to help owners build better business cases to install and operate larger generation capacity to mitigate major
environmental events that create extended power outages. Code-required power for emergency system is not designed to maintain buildings operational or remain occupied. Owners with the ability to generate enough power to continue to operate can control the outcome of their business during contingency situations.
Value add is different from value engineering. While value engineering focuses on achieving the essential functions of a building at the lowest life cycle cost, a value-add engineering strategy focuses on using the building systems to create financial value for the owners. There are many other opportunities, such as microgrids, renewable energy generation, co-generation, building automation, etc. that owners can explore to generate positive cashflow from building assets. cse
Simon Gandica, PE, PMP, is an electrical engineer and principal at Smith Seckman Reid Inc. with a focus on health care and industrial projects. He has directed multimillion-dollar projects from conception to occupation.
FIGURE 3: Peak shaving is the strategy that uses power generators to limit peak demand. Power generators serve partial load to lower peak demand.
Courtesy: Smith Seckman Reid, Inc.
BUILDING SOLUTIONS UILDING
Richard Vedvik, PE, IMEG Corp., Rock Island, Illinois
Existing generators: Extending service life strategies and reuse case studies
Due to long lead times, maintaining or relocating existing generators is a possible solution to the supply chain problem
There are a lot of standby generators that are in-use in both Level 1 and Level 2 emergency power supply, as defined by NFPA 110: Standard for Emergency and Standby Power Systems, systems that most professionals would classify as “beyond useful life” due to age or number of hours ran.
At the time of publication, lead times for generator sets are beyond 70 weeks due to myriad shortages. Many facilities are looking to extend the life of the equipment they have or find new uses for used equipment. Existing equipment locations can be improved upon, which can extend useful life and improve system reliability.
Improving existing electrical system locations for a generator
• Review strategies for maintaining existing electrical equipment.
• Consider all aspects of existing generator installations.
• Learn about options for standby generator relocation.
The locations of EPS and emergency power supply system equipment as defined in NFPA 110 are typically located in unconditioned spaces, which reduces longevity. If the EPSS equipment room lacks adequate heating or cooling, fan coil or blower coil systems, or mini-split heating, ventilation and air conditioning systems can be added to extend useful life and comply with NFPA 110-2019 Section 7.7. Environmental factors of concern include the temperature and humidity ranges and dirt
and dust accumulation within the room(s). EPSS rooms that lack sufficient HVAC shorten useful life of the equipment. Because EPS rooms typically have direct venting to the outdoors, they have the largest fluctuations in temperature and humidity while also having high dirt accumulation.
For a standby generator EPS, these environments affect the useful life of rubber hoses, gaskets, seals and pads. Generators with unit-mounted radiators have enhanced needs for exterior cooling and combustion air and pull large amounts of unconditioned air from the exterior. Even when the exterior louvers are closed, they lack adequate seals.
NFPA 110-2019 addresses the concerns of cold temperatures in Section 5.3.5, which requires maintaining 40°F when the EPS is not operating. If an existing EPS room lacks adequate HVAC equipment, adding supplemental heating and cooling can improve reliability.
The generator starting batteries are an important part of the system, and battery life is heavily impacted by ambient temperature. Best-battery systems, which provide additional redundancy, and high-quality battery chargers can be added to improve system reliability.
Additionally, electrical raceway or conduit is a pathway of air transfer, and it is not common to provide putty seals in conduit located “indoors.” When EPSS equipment is located in rooms with temperature and humidity fluctuations, condensation can occur in the EPSS distribution equipment where feeder raceways serve air-conditioned spaces.
Conversely, in cold climates, cold air can enter from the EPS or EPSS side and travel down raceways and cause condensation in the warm, conditioned spaces served. Both situations are affected by building pressurization, which tends to be more negative than positive due to the energy required to condition ventilation air in extreme cold or heat seasons. In either case, adding putty to the raceway system(s) can resolve the unwanted air transfer.
The 2020 edition of NFPA 70: National Electrical Code addresses flooding concerns in 700.12(A) and (B), aligning with NFPA 110 Chapter 7 and
Insights
Generator Insights
u Improving existing electrical system locations, especially temperature in those locations, can help improve battery life of generators, which is heavily impacted by ambient temperature.
u Evaluating existing airflow and existing fuel oil can help both generator set capacity and maintain fuel integrity.
u Reusing an existing generator puts the designer at an advantage because exact dimensions and configuration are known.
NFPA 99: Health Care Facilities Code section 6.7.1.2.6. This is a more difficult environmental situation to solve, and the severity of the concern depends on the location of the building.
Note that this section is not limited to natural disasters, but also considers failure of piping for pressurized water systems, such as fire protection, chilled water, stormwater or steam. Where foreign systems are routed in a way that could put the equipment at risk during piping failure event, relocating mechanical piping should be cheaper and quicker than replacing and relocating electrical equipment.
Evaluating existing airflow in a generator
Unit-mounted radiators require a lot more exterior air to be brought into the EPS room than remotely located radiators. While the impacts of temperature and humidity were addressed above, existing airflow restriction also requires attention. The unit-mounted radiator is rated for a maximum pressure drop that can be experienced before generator set de-rating occurs. The preferred arrangement is one in which airflow passes by the generator and engine block before going through the radiator. Some rooms may have intake louvers on side walls where airflow does not pass by the generator and only partially cools the engine block, which shortens useful life. A similar concern occurs with parallel generators and the arrangement of intake air louvers, with concerns that some radiator fans will have less restriction than others, and the pressure drop across intake air pathways increases when all generators are running.
Factors that influence airflow pressure drop, include intake louver free area and design, air pathway configuration, and discharge plenum design and louver free area (see Figure 1). Plans for future growth should include additional airflow for the anticipated systems. Intake air and discharge air
pathways can be modified and louver free-area can be increased in existing rooms. One strategy is to replace existing louvers located within the building envelope and providing a new plenum on the building exterior with a new, larger louver.
Evaluating existing fuel oil
Because standby diesel generator sets spend a lot of their life waiting to be used, the fuel will need to be routinely cleaned to maintain fuel
installed on an existing fuel oil system for improved reliability of relocated generators. Courtesy:
FIGURE 1: A diagram showing generator cooling airflow pathway and routing for minimal pressure drop and maximum cooling performance. Courtesy: IMEG Corp.
FIGURE 2: Image of fuel polishing system
IMEG Corp.
BUILDING SOLUTIONS UILDING
integrity. It is not common for existing installations to include active fuel polishing systems. These systems are not very expensive and prolong fuel life, save money on third-party fuel treatments, and extend generator fuel filter life and generator reliability. Even existing systems will benefit from cleaner fuel (see Figure 2).
The route that existing fuel lines take can affect system reliability. The ideal scenario is for gravity drainage of returned fuel, as noted in 2022 NFPA 110 Section 7.9.4. This means that fuel storage is routed below the lowest level of the generator and
day tank return connections. This arrangement is benefited by recessed trenches for fuel line routing to eliminate trip hazards within the room.
When fuel return piping is routed above the level of the generator and the day tank, then a fuel oil return pump is required, along with solenoid valves and sometimes check valves. It is prohibited by 2022 NFPA 110 Section 7.9.4 to install the day tank at a level above the generator, as additional check valves are required to prevent flooding the engine. Standby generator fuel oil storage systems may be shared with boil-
CASE STUDY: Reuse and update EPSS equipment
IN THIS HOSPITAL, a temporary generator allowed existing gear to be updated
PROJECT GOALS: Increase generator capacity and reuse existing paralleling gear with the help of a temporary generator.
EXISTING CONDITION: A hospital facility of more than 140 beds had two 480/277 V 3-phase, 4-wire standby diesel generators sized 700 kW and 900 kW. The existing generators, paralleling switchgear, and emergency distribution were in the same room, which is allowed by NFPA 110 Article 7.2.1.1. The existing paralleling switchgear was not sized for future expansion and needed to be replaced. To save cost and not have to wait for replacement switchgear, the existing paralleling gear was planned for an upgrade.
REUSING EXISTING PARALLELING GEAR: The existing 700-kW generator set was being replaced with a 1,500-kW diesel generator set. Due to the additional generator size, the radiator’s discharge louver was located at the building’s exterior wall and a new discharge plenum and louver was placed on the exterior of the existing building (see Figure 3). Additional intake air was required, and new intake louvers and air pathways were added to the space, as defined in NFPA 110, Article 7.7. The existing fuel oil-storage system was reused, and the project added fuel-polishing equipment to maintain fuel quality.
The existing paralleling switchgear had bus amperage that was too small for the additional generator load. Instead of replacing the switchgear at a higher cost and with longer
FIGURE 3: Temporary cabling connecting a temporary generator to campus distribution to allow for upgrading of existing paralleling gear. Courtesy: IMEG Corp.
lead times, additional bus layers were added to increase the amperage from 2,000 to 3,600 amps This modification was performed by the switchgear manufacturer, on-site. This upgrade allowed for a second 1,500-kW generator to be added in the future. Generator beakers were replaced with a larger frame size for sufficient future capacity. The engine controllers were both upgraded. An additional distribution section was added to allow for future loads and provide a feed to an external load-bank connection cabinet.
To accomplish this task, a 1-megawatt temporary generator was required to provide standby emergency power during the three-month switchgear upgrade and testing duration. To move the campus to a temporary, external, standby generator set, the existing feeders needed to be extended with flexible locomotive cabling (see Figure 3). This was accomplished with careful coordination with the utility and hospital personnel to control outage impacts.
The state public health department was notified of the plan, and they requested detailed sequences for each feeder outage to ensure patient safety was maintained. The generator control and start/stop cables were extended to the temporary unit.
CASE STUDY: Patient bed tower addition
THE ELECTRICAL DESIGN TEAM relocated generators for a hospital addition
PROJECT GOALS: Provide additional standby generators for a hospital building addition.
EXISTING CONDITION: A hospital campus added a 144,000-square-foot patient tower to the existing campus. This new tower included approximately 80 patient beds and was independent from the existing campus central plant. The existing campus had three 400-kW standby diesel generator sets operating at 480 V and they were loaded to 70% capacity. The design team considered revising or upgrading the existing system but decided that a separate emergency power supply and emergency power supply system with room for future growth would provide more flexibility.
DESIGNING AROUND EXISTING GENERATORS: The same client had a pair of 600 kW diesel generators with 4,160 V output located at a different location and they were available for relocation. The same design team had recently replaced the two 4,160-V, 600-kW generators with 4,160-V, 1,000-kW generators and the team was familiar with their specifications and knew they were available. The 4,160 V output allowed for a remote location over 1,000 feet away, in a building adjacent to the existing campus generators.
This required early planning to ensure the electrical rooms in the addition could accommodate interior transformers integrated into unit substations. A dedicated room was created to house the paralleling gear separate from the generators to allow for a clean, conditioned, place to operate electrical gear. The generator room is heated and the EPSS room has heating and cooling with a dedicated fan coil unit.
The air intakes were located on the opposite wall from the unit-mounted radiators to provide ideal airflow and minimize pressure drop (see Figure 4). Acoustical louvers were used at the generator discharge with consideration given to the calculated property line noise levels. Additional considerations include
ers, which provides a secondary fuel source for building heating systems. This additional system increases the complexity of piping, controls and routing. 2022 NFPA 110 Section 7.9.13 prohibits actuated valves on Level 1 EPSS
Evaluating existing generators for reuse
When an existing generator set is available for reuse or repurpose, the design team needs to coordinate with the existing manufacturer and client to determine if the existing selection is the right equipment for the proposed application. The obvious specifications are voltage and power ratings, fuel type, noise levels and physical dimen-
4: Two relocated 4,160-V, 600-kW diesel generators in a remodeled space that was planned for three 1,000-kW generators.
Courtesy: IMEG Corp.
providing in-floor trench for fuel oil piping and the addition of a fuel polisher to the existing long-term fuel storage system.
The relocated generators were temporarily stored with the manufacturer due to the schedule difference between the replacement project at their original location and the reuse project location. The manufacturer was asked to review the generators and evaluate the physical condition of consumables. When relocated, new batteries, cables and a new best-battery charging system was provided.
The new location provided new 4,160 V paralleling gear that communicated with upgraded engine controllers. The manufacturer provided new digital engine controllers initially, but they had trouble with consistent paralleling so analog engine controllers were eventually provided.
The generators have been in service for four years now and have proven to be reliable, thanks to the improvements made and the planning put into the new location.
‘ The route that existing fuel lines take can affect system reliability. ’
sions. The existing overcurrent protection needs to be evaluated, and the replacement of the primary breaker may be required to ensure selective coordination with the proposed down-stream distribution.
One benefit of reusing an existing generator is knowing the exact dimensions and configuration
FIGURE
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paralleling is planned.
’
you have to work with. When specifying a generator with multiple manufacturers, the designer needs to account for all possible configurations. Besides verifying the physical size, the physical condition needs to be reviewed. Expect that the existing engine controller will need to be upgraded or updated, especially if paralleling is planned.
Generators in exterior controllers should be evaluated for rust or corrosion, and the noise level from the generator needs to be reviewed with the new local noise and emission ordinances. The benefit of knowing what is there can be offset by the downside of being hindered by what is there. For example, heaters and operable dampers may not be present with older, exterior generator enclosures.
Variable frequency drives (VFDs) are used to control pumping systems. But VFDs create a motor shaft voltage that discharges through the bearings, blasting millions of pits in bearing surfaces. Both motor and pump bearings are at risk. These discharges oxidize the bearing grease and cause bearing uting, premature failure, and costly downtime.
Protect motor bearings with AEGIS® Shaft Grounding Rings
By channeling VFD-induced discharges safely to ground, AEGIS® Shaft Grounding Rings prevent electrical bearing damage. Proven in millions of installations worldwide, AEGIS® Rings provide unmatched protection of motors against electrical bearing damage, motor failure, and unplanned downtime.
When reviewing an existing generator for reuse, it is recommended to go over the maintenance records to evaluate the history of testing, fluid changes, filter changes and fuel treatments. Consumable items include hoses, filters and gaskets, and the generator vendor can assist in evaluating the physical condition of foam or rubber materials.
Engine oil analysis can be a good idea as it can help evaluate the internal condition of the engine by looking for excessive contamination or bearing materials that can indicate potential future failure. Other consumable items include batteries, cables and chargers, all of which should be replaced if they are at or approach the end of useful life.
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If the generator is an indoor model, the combustion air and cooling air requirements need careful attention, and the new location needs to accommodate airflow pressure drop and cubic feet per minute requirements. cse
Richard Vedvik, PE, is a senior electrical engineer and acoustics engineer at IMEG Corp. He is a member of the Consulting-Specifying Engineer editorial advisory board.
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Breanna Robertson, EIT, WSP USA, Dallas
CASE STUDY:
Electrical room design for hospital campuses
A hospital in the Southeast had several electrical infrastructure design considerations
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Objectives Learning
• Learn about master planning design and expectations with owners.
• Understand design considerations for electrical infrastructure in a campus expansion.
• Look at electrical room layout considerations.
Amajor pediatric health care provider in Atlanta is expanding its campus and will greatly increase the number of patient beds to its existing portfolio. WSP USA is the primary mechanical, electrical and plumbing engineering firm for this 1.44-million-squarefoot expansion that began master planning in 2017 and is set to open to the public in 2024.
This expansion includes a new central plant (50,000 square feet), standalone hospital (1.3 million square feet), clinic building (500,000 square feet) and parking garages. During the pre-design and master planning phase, the engineering team needed to consider various campus infrastructure and expansion scenarios.
Master Planning and utility coordination
Before designing the room layouts of the buildings, major site and electrical utility capacity coordination and planning needed to occur. The owner provided parameters for the buildings and the desired bed count for the initial build and various expansion scenarios. These gave the design team a starting point to begin spatially locating various buildings and infrastructure within the site to optimize the layout of the new campus.
During master planning the key question to answer is, ‘What are we currently designing to, and what future capacity do we need to plan for in our design?’
The answer is key as it will drive the entire design and affect the initial central plant capacity and ability for expansion to serve the current campus plan, as well as any future expansions. The electrical system capacity was going to include serving the initial buildings, as well as planned shell floors withing the initial build and future
FIGURE 1: Campus site plan of the new expansion for a pediatric health care provider. Courtesy: WSP USA
tower expansions and additions to the hospital and clinic building.
At this stage, the architectural design partners on the design team started working toward various blocking and stacking diagrams that helped inform engineering and infrastructure calculations. This stage of design is crucial for the engineering team to coordinate with the architect on space requirements for equipment rooms and placement of infrastructure routing. To provide this information to the architectural design partner, the engineering team had to first determine how to best distribute electrical, mechanical and plumbing throughout the building to meet the demand of the various departments on each floor in each blocking and stacking option.
Looking at the hospital, which is 19 stories, locating central electrical, mechanical and plumbing systems on just one floor was impractical. Therefore, it was determined that there was a need before one or more interstitial floors to serve portions of the hospital, like other high-rise buildings, such as residential or office towers.
Concurrent with the blocking and stacking analysis, the electrical engineering team sets up meetings with the utility company, Georgia Power Co., to discuss incoming power options and capacity requirements. Due to the size of this expansion,
which from preliminary calculations estimated the system size at approximately 32 MVA, GPC determined that infrastructure improvements and reconfiguration of their network system would be needed to serve the campus demand.
Through GPC’s analysis, it was determined that having the incoming power enter the north side of the site was preferred. This incoming utility information, therefore, helped to drive the decision to locate the central plant on the north side of the campus.
Once the location for the central plant was established, there were two options to consider for how to distribute power to each of the campus buildings. Option one consisted of an incoming utility transformer yard provided by GPC located near the central plan with facility owned mediumvoltage distribution to multiple unit substation locations to serve various portions of the buildings. Option two consisted of a GPC provided transformer and incoming utility feed to each building (see Figure 2).
Through a Choosing by Advantages A3 process, the design team and owner selected option one. Therefore, a single GPC utility transformer yard (primary 20 kilovolts, secondary 5 kV) would be located adjacent to the central plant and be the main supply for the entire campus.
FIGURE 2: A3 of utility options for the campus after coordination meetings with Georgia Power to determine how they could provide utility power to this expansion. Courtesy: WSP USA
Insights
csemag.com
Electrical room design
u When figuring the blocking and stacking analysis, it is important for the engineering team to coordinate with the architect on space requirements for the electrical room and placement of infrastructure routing.
u Drawbacks to using custom sized equipment in this situation were first cost and lead time implications, life cycle maintenance cost and complexity.
u An important part in the design of large-scale generator plants, especially in urban areas, are the acoustic and pollution control considerations. In this case, the team enhanced pollution control and sound attenuation was included in the central plant design.
BUILDING SOLUTIONS UILDING
Electrical distribution design
Once the service location was determined, the design team focused planning efforts on the location and quantity of interstitial spaces to appropriately serve the hospital departments. There were multiple factors to consider in optimizing the placement and square footage served from each interstitial service location throughout the building.
First, is selecting noncustom equipment sizes for unit substations. Using custom-sized equipment can cause first cost and lead time implications, as well as life cycle maintenance cost and complexity.
‘ During this process, it’s important to have engaged with the facility maintenance team on the complexity of the electrical system.’
Second, the team considered the load demand of each floor. In the main hospital design, the basement was designated for high-power density spaces, such as the central kitchen, laboratory and supply chain. Floors one through four were diagnostic and treatment areas, such as radiology, surgery and the emergency department. Floors five through 19 were designated for various acuity patient room floors and support spaces.
Based on this density distribution, the team conducted a concurrent analysis of how each segment of the building would be served with power and heating, ventilation and air conditioning. Ultimately the team agreed on two interstitial service floors on levels three and 11, which were 75% mechanical, electrical and plumbing spaces, and an additional main normal and emergency electrical room in the basement. Electrically, this allowed the system to feed upward from each level that included the main electrical rooms.
During this process, it’s important to have engaged with the facility maintenance team on the complexity of the electrical system. In the example of this project, the owner was very keen toward resiliency as this will be the largest children’s hospital in the southeast region of the United States. This led the design to include multiple levels of resiliency. Multiple utility feeds were planned to the main medium voltage switchgear in the central plant, as well as providing loop feeds to unit substations and
including a digital power monitoring system at all major pieces of equipment. Each project has varying criteria and budget considerations; therefore, it is important to discuss and document expectations and owner standards early in the design process.
Central plant system
The normal incoming power was coordinated with the local utility provider, and this conversation led to the final decision of providing a networked utility transformer yard adjacent to the central plant on the north side of the site. This transformer yard included eight utility transformers with redundant units if one of the transformers were to fail. From this yard, multiple 5 kV feeds enter the central plant on Level 00 into the customer supplied 5 kV normal system switchgear. This gear then serves 5 kV feeders to the central plant substations, as well as loop feeds to the hospital and clinic building unit substations.
One floor above the normal service entrance were the generators and associated essential system paralleling gear and unit substation. The system was designed for the emergency system to back up approximately 40% of the facility load internally, which equates to approximately 12.7 kVA (or 11.5 kW). Based on this demand load, and the distribution feeder distances, the team decided to provide 5 kV generators.
Medium voltage feeders on the normal and emergency system reduced the quantity and size of conductors routed to the remote unit substations throughout the campus.
While the initial design for the essential standby system is sized for approximately 40% of the campus load, the owner’s criteria directed the design team to plan for expansion of the system to include backing up 100% of the campus at some point in the future. Therefore, the design team planned space to add future generators and associated switchgear in the future.
Another important consideration in the design of large-scale generator plants, especially in urban areas, are the acoustic and pollution control considerations. The team included both an acoustics and wind consultant to assist the team in analyzing the generator plant location and accessories to control sound and pollution. During these conversations, it was decided to locate generators indoors to avoid
noise issues and conceal all the equipment at the central plant. In addition, enhanced pollution control and sound attenuation was included in the central plant design.
The generators were located on the second level of the central plant (Level 01) to allow exhausting means directly up through the roof and allowed for an entire wall of mechanical louvers with sound attenuation to have a crossflow across the generators for optimum performance.
Main hospital electrical system
The basement, level three and level 11 where the floors chosen to locate main electrical equipment to serve the associated floors above. The campus schematic one-line shows loop feeds between normal substations and loop feeds between the emergency substations.
On each level the normal electrical rooms were designed with double-ended substations, while the emergency electrical rooms have single-ended substations. While it was an option to provide double-ended substations for the emergency system, it was decided by the design team and owner to not provide this as it wasn’t required to meet the project’s resiliency needs, and therefore the costs outweighed the benefit.
A central uninterruptable power supply system was designed for the hospital to serve critical loads that the owner’s criteria stated could not withstand a momentary loss of power awaiting generator startup. These sensitive systems included all the data rooms, 80% of imaging equipment, all isolation panels for procedure and operating rooms and a receptacle on each intensive care patient room headwalls.
To meet this demand, two 900 kVA UPS systems, each with an N+1 module redundancy, were selected. One UPS served the dedicated data loads, while the other UPS served the patient care and imaging loads.
Given the size of the hospital floorplates, multiple branch electrical rooms were required on each level. The design included placing one electrical room in each smoke compartment. This scheme was chosen for several reasons.
First, as each smoke compartment is a maximum of 22,500 square feet, this matches the typical area that is optimal for branch circuit conductor lengths to meet voltage drop requirements without exceeding #8 AWG conductors.
Second, the team planned to place the fire alarm notification panels in each electrical room, which allows for one notification appliance circuit panel within each smoke compartment. Thus, fire alarm circuits would not need to cross smoke compartment boundaries and could minimize the use of costly two-hour rated fire alarm cable systems required to meet survivability codes.
Clinic building
The clinic building was originally planned to be a 10-story 325,000-square-foot building with planned future floor additions above. However, future moved to current design and the building will now be a 17-story 500,000-square-foot building when completed at the end of this project.
Given the height of this building an interstitial floor was designed for the mechanical system to distribute air throughout the building. Electrically, due to lower load demand from an ambulatory care facility, it was able to be served through a main normal and emergency room in the basement, each with a single-ended substation.
Because the design team was aware of the future growth early in design, future capacity was already incorporated into the electrical system so no other major equipment was necessary to meet the demand of the additional seven floors. cse
Breanna Robertson, EIT, is an electrical engineer with WSP USA and primarily focuses on health care design on projects throughout the United States.
FIGURE 3: Schematic medium voltage one-line of campus expansion. Courtesy: WSP USA
Kevin Miller, PE, LEED AP; and Davis Clum, Certus Consulting Engineers, Dallas
Sustainable condenser water system strategies
The condenser water system has a big impact on efficiency, long-term maintainability and total cost of ownership for the chilled and condenser water system
In a condenser water system, there are several components that impact energy consumption of the overall chilled/condenser water system:
• Chiller compressors.
• Cooling tower fans.
FIGURE 1: Proper condenser water treatment is key to reducing scale buildup over time. This photo shows a new cooling tower alongside 10-year-old cooling towers and the scale buildup on the fill over timae. Courtesy: Certus Consulting Engineers
• Condenser water pumps.
• Water quality.
It is appropriate to briefly discuss the total system efficiency considerations that are typical in any condenser water system selection and design.
Condenser water supply temperature control
Fundamental to efficiency of a chilled water system is compressor lift. Lift, or head pressure, refers to the difference in refrigerant pressure between the condenser and the evaporator. The higher the lift, the more work the compressor is required to do.
The chilled and condenser water temperatures both affect the lift. Reducing the entering condenser water temperature and/or increasing the leaving chilled water temperature will reduce the amount of work required by the compressor. While one strategy to decrease lift may be to reset chilled water supply temperature, there will be upper limits in any application.
In some applications such as health care where low supply air dewpoint control is required, special care must be taken in resetting chilled water supply temperature. With constant chilled water temperatures, colder condenser water temperature still results in significant reduction in compressor energy of the chiller. A good rule of thumb is 2% kw/ ton reduction per 1°F reduction in condenser water supply temperature.
Assuming a constant 70% load or 350 tons, let’s compare the efficiency and power consumption with condenser water supply temperatures of 85°F and 65°F.
Power consumption at these two points is:
@85°F CWST: 350 tons x 0.5494 kw/ton = 192.29 kW
@65°F CWST: 350 tons x 0.3276 kw/ton = 114.66 kW
The reduction is power consumption at the lower CWST is 192.29 – 114.66 kW = 77.63 kW, which equates to a 40% reduction. This is in line
with and helps to validate the rule of thumb mentioned above (approximately 2% increase in efficiency per degree of CWST reduction).
At any given ambient wet bulb temperature, producing colder condenser water requires additional cooling tower capacity resulting in increased tower fill and/or tower fan horsepower. Careful coordination with cooling tower manufacturer is recommended to optimize the tower size versus fan horsepower. Cooling tower fans operate via on/off controls or modulate via variable frequency drives to maintain a condenser water supply temperature.
VFDs provide the most energy efficient method of controlling the fans. While this cannot be ignored in optimizing the design of the system and controls, cooling tower fan energy is significantly less per ton than chiller compressor energy. In general, it is fair to say that the goal for an efficient system should maintain the lowest approach temperature possible.
Said another way, to optimize system efficiency, variable speed cooling tower fan control should, in general, aim to control the CWST to the lowest temperature possible given the ambient wet bulb.
Optimizing condenser water temperatures
With a constant temperature differential, reducing condenser water flow rate increases the efficiency of the pumping and cooling tower system, while reducing the efficiency of the chiller. While the most efficient flow rate (gallons per minute (GPM)/ton) cannot be generalized without a full evaluation of the system and cooling load profile, the once standard 3 gpm/ton (85°F/95°F condenser water entering/leaving temperature) is no longer the best design flow for all systems.
A full system model and accounting for piping savings and reduced pumping energy may show 2 or even 1.5 gpm per ton to be optimal. Further, with improvements in chiller efficiencies and the cost effectiveness of VFDs, variable condenser water flow is increasing in viability for consideration as part of overall plant optimization.
Other energy conservation strategies impact the proper condenser water system selection and
design. Strategies like waterside economizer, airside economizer and heat recovery chillers cannot be individually discussed in sufficient detail here. The key point is that these types of systems affect the overall load and energy profile of the cooling towers, pumps and compressors and must be evaluated in concert to see the full picture of efficiency.
To summarize, the components and fundamental strategies discussed thus far are all interrelated. Each of these must be evaluated and modeled as a complete system using the building cooling load profile and weather data and actual equipment efficiency based on specific selections. The “right answer” is also dependent on many other factors including equipment and piping costs, utility rates, expertise of plant maintenance staff, availability of service, etc.
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FIGURE 3: Lift can be described as the work required by the chiller compressor. This diagram illustrates the refrigeration cycle and the relationship between compressor lift and system enthalpy. Courtesy: Certus Consulting Engineers
Objectives
• Obtain an overview of basic condenser water design considerations.
• Learn the opportunities to improve water quality and conserve water through system design.
• Understand the relationship between various strategies and components and the importance of a fully integrated system approach.
FIGURE 2: Basic piping diagram for a typical chilled water/condenser water system. Courtesy: Certus Consulting Engineers
BUILDING SOLUTIONS UILDING
FIGURE 4: Cycles of concentration in a condenser water system refers to the number of times minerals in the water are concentrated through evaporation. This graph illustrates the relationship between cycles of concentration and the makeup water requirement.
Water quality management
In addition to design selections and strategies, operations and maintenance programs have a significant impact on overall water system efficiency, environmental quality, water usage and longevity of equipment and components.
Water quality management is often viewed as maintenance, more than design and has a large impact on the lifecycle cost of the overall system. While most operators would agree that controlling scale, deposits and biological fouling is important to limit obstruction and corrosion of tubes, pipes and components, the magnitude of the impact of a small amount of scale on efficiency is often underestimated.
As water is evaporated in a cooling tower, the concentration of dissolved solids becomes greater. When the solubility of a mineral is exceeded that mineral is deposited on a heat transfer surface or pipe as scale.
The thermal conductivity of minerals in the condenser water is less than that of copper condenser tubes in a chiller. Calcium carbonate, the most common condenser water scale, has a conductivity of about 0.24 times that of copper. A scale layer of 0.02 inches on the condenser tube walls can reduce the thermal efficiency by 15% resulting in significant energy costs.
The concentration of minerals and contaminants in the recycled condenser water can be limited by intentionally wasting some of the water to drain, referred to as blowdown, or BD. When this water is replaced with fresh makeup (identified
as MU) water, the concentration is reduced until evaporation (in this case E) occurs in subsequent cycles of the water through the system.
Cycles of concentration can be defined as the number of times that the minerals in the makeup water are concentrated in the condenser water by evaporation. COC can be calculated by using a conductivity meter to measure the conductivity of the condenser water and dividing by the measured conductivity of the makeup water. Another simple way to measure cycles with proper meters installed, is to divide the volume of makeup water by blowdown.
COC = MU/BD
The equation for this simplified method of measuring cycles best illustrates what the cycles is really telling us and the benefit of cycling. A higher COC indicates that a larger percentage of the total makeup water was to replace evaporated water and less was to replace blowdown.
MU = E + BD
Less blowdown conserves water. In addition to reducing the environmental impact, less makeup water results in a savings of water and sewer charges, as well as lower chemical treatment costs as less of any scale and corrosion inhibitors used are dumped to drain.
In general, between three and six cycles is found to be an economical range for condenser water systems. The optimum number of cycles is highly dependent on the makeup water quality, water and sewer rates and chemical costs. The optimum COC (maximum economic cycles) should be evaluated in a cooperative effort involving the operator, local water treatment vendor and design engineer.
Cycle control
Probably the most common method of controlling cycles is conductivity control. With the method, the conductivity of the condenser water is constantly measured. When it reaches a preset level, the automatic blowdown valve opens, dumping high mineral content water to drain. As this water is replaced with makeup water, the conductivity drops. When it is below setpoint, the blowdown valve closes.
One potential problem with conductivity-controlled blowdown can occur with hard makeup water and is often overlooked. When scale forms, calcium carbonate is removed from the water and the conductivity is reduced. As a result, the conductivity controller does not open the blowdown valve, the water is overcycled and additional scale is generated. This potential must be considered when looking at the overall COC strategy and method of control.
The second method, proportional blowdown, involves measuring makeup and proportionally controlling blowdown to reach a predetermined COC number. As most facilities will already have metering in place on makeup and blowdown to obtain evaporation credits on their water bills, this method is often the simplest and most economical. The potential downfalls with this method are that, unlike conductivity control, it cannot compensate for changes in makeup water quality or for small leaks in the system.
Each system has a unique set of parameters involving cycles, inhibitor chemistry and dosage, makeup and blowdown that results in the lowest total operating cost.
The chemistry and quality of makeup is a key consideration that is often left to be part of the equation as the water treatment vendor develops a recommended chemical treatment program for the installed system. Water hardness is one property that has a significant impact on necessary water treatment and deserves a careful evaluation of options during design.
load data (kW/ton)
Soft water for condenser water makeup
Calcium hardness, alkalinity, pH and water temperature determine the solubility of calcium carbonate. Most cooling towers use raw municipal water for makeup, sources of which vary in quality. This is most commonly addressed with limiting COC, injection of chemical scale inhibitors or injection of mineral acids. Using ion exchange softening for cooling tower makeup is less common but can help reduce scale while also controlling corrosion and conserving water by allowing higher COC.
There are often claims made that soft water is more corrosive than hard water, based on the theory that a thin layer of calcium carbonate acts as a buffer to protect metals. While it is true that a very thin layer of calcium carbonate can help inhibit corrosion, it is not true that soft water universally and directly attacks metal surfaces. Corrosion is dependent on many variables including pH, alkalinity, dissolved solids, oxygen and temperature.
With the classical use of sulfuric acid for alkalinity and pH control, very tight control of the acid concentration is required and the pH is often controlled to levels below the pH range for corrosion control of copper and steel. In addition, corrosion inhibitors are then required due to the aggressive nature of acids.
When evaluating the use of soft water for cooling tower makeup, softener regeneration wastewater and the cost of salt should also be considered.
Condenser water systems
u When designing a system, there are several typical condenser water efficiency design considerations.
u Integrated condenser water systems tend to perform better and be more efficient.
As with all strategies, the complete system must be evaluated. Overall, the use of soft water for cooling tower makeup generally reduces total operating costs, extends the life of equipment and helps to protect the environment and promote water conservation.
Solids filtration
Cooling towers make great “air scrubbers.” With a large amount of air moving through a cooling tower, significant amounts of airborne dust and debris are introduced into the condenser water. Suspended solids contribute to scaling, biological fouling and corrosion throughout the condenser water system. With a large amount of dirt settling out into the basin, solids are also a large contributor to cold water basin corrosion.
Sweeper piping and sand or tangential solids separators are an effective method of removing dirt from the system at the source (the cooling tower basin). Alternatively, side stream separators remove solids from within the condenser water piping — constantly filtering a percentage of condenser water flow. Side-stream filtration is cost effective but does not prevent solids from settling in the basin. Implementing effective solid filtration is critical to extending the overall life and efficiency of the system and its components.
Condensate recovery
In most areas of the United States, water is a relatively low cost and a very effective heat transfer medium, making evaporative cooling towers the most effective means for rejecting heat into the atmosphere. Nonetheless, the cost of consuming, discharging and treating condenser water represents a significant operating expense and creative ways to reduce makeup water should be carefully evaluated on every project.
Normal air conditioning results in large quantities of cooling coil condensate, especially in
humid climates. Depending on the building layout and location of air handling units and cooling towers, this condensate is often able to be returned to the plant by gravity. Because the need for cooling tower makeup and generation of cooling coil condensate are simultaneous, all condensate recovered can be used for cooling tower makeup without any need for storage.
Cooling coil condensate does not contain dissolved minerals and is nearly pure. Therefore, recovering this water for use in cooling tower makeup can greatly reduce blowdown (increase COC) and reduce chemical treatment cost. It also can reduce or eliminate the need for softening when it can be shown that cooling coil condensate will always be available.
In evaluating the return on investment of condensate recovery, the overall system must be evaluated and modeled with the airside systems, load profile and weather bin data. First cost of the condensate recovery system must also take corrosionresistant materials into consideration for piping and storage tanks because of the corrosive nature of such pure water.
Various design strategies and components of a condenser water system significantly impact the overall life cycle cost, efficiency and longevity of the complete chilled/condenser water system. Proper evaluation requires that all aspects and strategies be analyzed together as a complete system and that all stakeholders are involved in the evaluation and decision-making process. When this occurs, enhancements with relatively short payback can also have a positive impact on the environment and simplify maintenance for the life of the building. cse
Kevin Miller,PE, LEED AP, is a principal at Certus Consulting Engineers. With 24 years of experience, specializing in health care buildings, Miller is a founding principal and continues to bring technical expertise and provide creative solutions to the industry.
Davis Clum is a mechanical designer at Certus Consulting Engineers. Clum specializes in health care buildings. Clum has a passion for sustainable design and brings a creative and fresh perspective, working with industry partners toward innovative solutions.
FIGURE 5: This illustrates a basin sweeping piping system. Courtesy: Lakos Filtration Solutions
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BUILDING SOLUTIONS UILDING
Stet Sanborn, AIA NCARB CPHC, SmithGroup, San Francisco
Can heat pump hydronic systems aid in decarbonization?
There is increasing demand for all-electric heat pump-based heating hot water systems to replace traditional gas-fired boiler heating systems. How can it aid buildings and cities?
Within the past five years, there has been a rapid change at the local level as jurisdictions across the country have adopted aggressive building codes, reach codes and planning ordinances that have strongly incentivized building electrification if not outright required it for new construction. One of the critical enabling technologies for this decarbonization push has been wider adoption of heat pump-based space heating and domestic hot water systems, which if designed and applied appropriate-
TOSS? FIGURE 1: Local cities and states with decarbonization policies as of June 2022. Courtesy: Building Decarbonization Coalition
ly, can offer significant reductions in emissions as well as operating costs. Across the country, growing interest in reducing on-site greenhouse gas emissions has significantly increased the interest in these heat pump systems.
Although the most reported-on policy was the first in the nation building electrification ordinance in Berkeley, California, which was passed in July 2019, California as a whole has led this rapid decarbonization policy push with more than 55 cities enacting all-electric building codes, all-electric reach codes or electric-ready building codes, which covers nearly 20% of the state’s population.
More impactful than local policies in California, New York City’s Local Law 97 applies to existing buildings (a much larger segment of the building stock) and will rapidly drive adoption of heat pump technology in a much more challenging climate. Although not technically an electrification ordinance, it does place limits on emissions and heat pump technology is a proven path toward reductions in overall emissions.
Local Law 97 is one of the most ambitious plans for reducing emissions in the nation. Local Law 97 was included in the Climate Mobilization Act, passed by the City Council in April 2019 as part of the Mayor’s New York City Green New Deal. Under this groundbreaking law, most buildings over 25,000 square feet will be required to meet new energy efficiency and greenhouse gas emissions limits by 2024, with stricter limits coming into effect in 2030. The goal is to reduce the emissions produced by the city’s largest buildings 40% by 2030 and 80% by 2050. The law also established the Local Law 97 Advisory Board and Climate Working Groups to advise the city on how best to meet these aggressive sustainability goals.
Nationally, in July 2022, ASHRAE released its position document on decarbonization. This posi-
Objectives Learningu
• Review regional codes and standards that are driving reductions in operational carbon emissions.
• Understand key performance drivers that impact efficiency and resulting grid emissions for heat pump-based heating systems.
• Learn to develop strategies to increase performance and reduce cost for heat pump retrofits.
tion document, developed by the ASHRAE Taskforce for Building Decarbonization, sets out a roadmap to align internationally used energy standards with carbon metrics and drive fully decarbonization of new buildings as well as the aggressive retrofit of existing buildings. Key strategies included in the position document include electrification and use of high-efficiency heat pumps.
Although air-to-water air-source heat pumps are not the only heat pump technology that will need to be deployed, the aggressive nature of the emissions reduction requirements nearly requires the adoption of heat pump technology for all hydronic heating systems as a replacement for traditional natural gas fired boilers. Doing so in a cost-effective and efficient way requires more nuance than designing traditional boiler-based systems, as well as an understanding of the emissions factors for one’s local electrical grid.
If done well, these systems cannot only increase efficiency, but they can also reduce emissions, reduce operating costs and provide grid stability benefits as well. Maximizing efficiency and effective capacity of the heat pump systems will also reduce the impact of electrification on upstream infrastructure, including electrical switchgear and transformers.
Maximizing efficiency and reducing costs through thoughtful design
When designing an air-to-water ASHP system, several design factors will influence the efficiency of the heat pump. The decision with the largest impact that the design engineer will make is what supply water temperature regime to select. In general, heat pumps will have a higher coefficient of performance in heating mode the lower the supply water temperature is set to. There are few single-stage heat pumps on the market that can make supply water temperatures over 150°F efficiently.
Some R-513 refrigerant ASHPs can now make 160°F to 165°F efficiently. R-744 or CO2 heat pumps
FIGURE 2: Typical R-134a air-to-water air-source heat pump efficiency (coefficient of performance) as a function of outside air temperature and supply water temperature. Courtesy: SmithGroup
FIGURE 3: Mixed-use laboratory high-rise and residential high-rise combined on a central plant. A 8,760-hour heating and cooling load profile plotted to show the hours of simultaneous load (yellow) able to be met with a four-pipe heat recovery air-source heat pump. By adding a ground-loop exchange system, the project was able to augment the simultaneous load hours (green). This leaves only the red and blue loads to be met with the air-source function of the heat recovery ASHP. Courtesy: SmithGroup
are the one exception but are rarely used in space heating applications due to the high lift required on the condenser heat exchanger.
The second largest factor in determining the efficiency of an ASHP is the source outside air temperature. The colder the OAT, the lower the COP of the heat pump will be and the more energy it will use to deliver the same amount of heating to a space. In
Continued on page 36
BUILDING SOLUTIONS UILDING
CASE STUDY: Heat pump retrofit
AN HISTORIC religious building opted to decarbonize its heating system with a heat pump retrofit
The Unitarian Universalist Society of San Francisco has been at the corner of Geary and Franklin Streets in the heart of San Francisco since the mid-1800s. The sanctuary survived the great 1906 earthquake and fire, which destroyed a good portion of San Francisco. In the mid-1960s, the center went through a significant expansion, which added a child care center, classrooms, meeting halls, commercial kitchen, a library, chapel, as well as administrative spaces. The addition was in the brutalist modern style and consisted of very thick concrete walls and large portions of floor-to-ceiling glass facing a centrally organized courtyard.
During the center’s expansion, a central gas-fired, naturally aspirated boiler was installed and matched to a high temperature (180°F) hydronic distribution loop. The local distribution of heat was achieved through custom fan-coil units and small air handlers built into custom casework throughout the center all fed from the central heating loop.
For the better part of the past two decades, the society has been going
through incremental projects to improve building performance and reduce its overall environmental footprint. This included replacement of the pneumatic controls and thermostats for the heating, ventilation and air conditioning systems, LED lighting retrofits, an elevator replacement and green-power purchases. The latest project completed included the installation of a large solar photovoltaic system on the center’s roof.
The last remaining major project was to decarbonize the central heating system by retrofitting the building to heat pumpbased heating. Although many systems were considered, including variable refrigerant flow systems, the central heat pumps with hydronic distribution provided the best efficiency while also minimizing the risk of refrigerant leakage and its associated global warming potential.
Gathering data
One of the most important steps in completing a heat pump retrofit project is understanding actual energy use and load profiles. Because heat pumps are generally expensive and oversizing them can significantly degrade performance and life span,
it is critical to not just replace a boiler “likefor-like” based on name plate capacity.
For this retrofit, SmithGroup analyzed several years’ worth of utility data for gas and electrical usage and correlated it to measured outside air temperatures. Because only daily gas usage data was available, the team worked with the building engineer to review setback schedules, morning preheat behavior and complete on-site measurements to develop a synthetic annual, hourly heating demand profile based on the measured gas utility data.
One of the biggest challenges with this particular retrofit was the relatively high supply water temperature that the entire system had been designed around: 180°F. In addition, much of the distribution piping and equipment had just been replaced a few years before, so replacing and resizing the distribution equipment around lower supply water temperatures was not financially feasible. Most heat pumps designed for space heating hydronic systems cannot produce 180°F water efficiently, if at all.
With the goal of working within the existing pipe size limitations, SmithGroup worked with the building engineer to complete a wintertime temperature test over one full heating season. During the heating season, the supply water temperature was reduced by 5°F and held for two weeks. After the adjustment, all zones were verified to still be able to reach setpoint. In addition, staff were asked if they experienced any thermal discomfort.
After the two weeks, if all zones were able to maintain setpoint, the supply water temperature was reduced another 5°F and the procedure was repeated. Once the first zone was noted as unable to maintain setpoint, the temperature was increased back up by 5°F and held through the remainder of the full heating season. The resulting lowest feasible supply water temperature was 150°F.
This analysis, in conjunction with the measured gas usage data helped the team
FIGURE 4: Synthetic annual hourly heating demand derived from utility meter data. Courtesy: SmithGroup
FIGURE 5: Roof plan layout and electrical room upgrades required. Courtesy: SmithGroup
determine that the real peak heating load was roughly 30% below the name plate capacity of the boiler, even when a safety factor was included.
A new supply water temperature of 150°F led the team to select a new class of modular air-source heat pumps that use R-513 refrigerant. These new class of ASHPs can deliver supply water temperatures up to 165°F with outside air temperatures all the way down to 40°F. Although San Francisco is a relatively mild climate, the design day condition is closer to 34°F.
To complete an efficiency study, SmithGroup used the R513 ASHP’s performance curve (COP versus OAT) and mapped it against the local typical meteorological year (TMY3) file to produce an annual effective heat pump efficiency plot.
Heat pump solution
Another significant challenge in heat pump retrofit projects is finding adequate space for the ASHPs, as ASHPs require significant air exchange with ambient outside air. The original boiler on this project was tucked in a small subterranean room adjacent to the below-grade parking garage. Not only would that room not provide enough air circulation, but it also wasn’t big enough to fit the required number of ASHPs.
After analyzing the heating demand profile and the performance characteristics of the modular heat pumps, 10 modular R-513 ASHPs were designed around a common header setup. The original shaft that served the boiler flue was repurposed to provide a piping pathway to the roof, where the equipment could have adequate air circulation, as well as space for maintenance and servicing.
In addition to finding adequate space for the heat pumps, another significant challenge was being able to provide power to the new heat pumps. Because the existing building has never had air conditioning
FIGURE 6: Hourly CO2e emissions savings using an on-site heat pump versus existing boiler. Courtesy: SmithGroup
equipment, which is typically the load that would drive an electrical service sizing, the existing service and electrical panels were significantly undersized and would be unable to meet this new load. Although an expensive upgrade for the building, the change was welcomed by the facilities staff, as the existing panel and electrical service were original to the 1960s expansion and could no longer be serviced. In addition, the existing gear no longer met code-required front-side clearances, making it dangerous to service.
Energy efficiency impact
Through this retrofit project, the ultimate goal for the society was to reduce its carbon footprint to align with religious tenets. Electrification of space heating through the use of ASHPs is an exceptionally effective way to meet that goal. Using the short-term marginal grid emissions rates for Northern California, the change from an 85% efficient on-site boiler to R-513 ASHPs should result in an approximate 31% reduction in operating emissions annually when the project is completed in the coming two years.
Because the heating system is nonoperational during the summer months, the
majority of the emissions savings occur in the spring months, when the heating load is relatively low, the ASHP efficiency is high and the grid in Northern California is saturated with renewable solar energy. Even in the daytime hours of December and January when fewer renewable energy resources are available, using a heat pump still results in lower overall emissions, even though the heat pump is at its lowest efficiency and heating loads are at their highest.
To further drive down the operation emissions, the society has already joined a zero-carbon electricity program in San Francisco, which allows users to opt-in to a 100% renewable energy portfolio, effectively allowing the society to zero out its operating emissions as soon as the heat pump retrofit is complete. In addition, the organization is investigating expanding its solar PV array and potentially installing on-site battery storage to allow them to increase usage of the on-site renewable energy, further reducing the carbon footprint and increasing resilience to power outages.
BUILDING SOLUTIONS UILDING
FIGURE 7: United States map with color-coded ASHRAE climate zones and each independent service operator territory outlined. Air-source heat pump grid-emissions are directly impacted by the local source air temperatures and real-time marginal emissions rates during hours of operation. Courtesy: SmithGroup
Continued from page 33
addition to COP reductions during lower OATs, the capacity of the heat pump will also diminish with a reduction in OAT.
However, several recent improvements in heat pump technology, such as inverter drives and enhanced refrigerant injection have helped to mitigate those performance impacts. As the overall efficiency and supply water temperature regime are critical to overall performance, it is crucial to review the specified ASHP’s performance curves, as each heat pump and each refrigerant used by heat pumps have different performance curves.
For projects in colder climates, it becomes increasingly imperative that engineers appropriately select supply water temperatures for their systems that are as low as feasible. As an example, high-mass radiant floor systems can perform exceptionally well with supply water temperatures below 120°F. Ideally, they would be served by 110°F or lower heating hot water, which results in exceptionally high heat pump COPs, even in cold climates.
Engineers should also boost performance by taking advantage of heat recovery opportunities in their buildings. Although important in all building systems design, this is a key strategy, especially for cold climate designs using heat pumps. Many new ASHPs come in a four-pipe heat recovery configuration. This allows them to act in a similar fashion as a heat recovery chiller to cover simultaneous loads, able to produce chilled water as a byproduct
of producing heating hot water. When the loads are out of balance, the ASHP uses the air-source function to make up the nonsimultaneous load.
For internally load-dominated buildings in cold climates, this is an exceptional strategy to reduce the impacts of cold OATs, as the system is essentially moving heat out of the core in the form of cooling and into the perimeter zones in the form of heating. For projects with the ability to use groundsource heat pumps, which are incredibly efficient, the design engineer can combine water-source heat pumps and four-pipe ASHPs in a hybrid configuration, to maximize heat recovery and efficiency. Other sources of heat recovery can include exhaust air streams and even sanitary waste streams.
Reducing operating costs is also a significant driver in increasing system efficiency, whether it is through supply water temperature design decisions or maximizing opportunities for heat recovery. Each project team should review local gas and electric utility rates to determine the COP that will provide cost-parity in moving to a heat pump-based heating system.
When comparing local natural gas costs and boiler or furnace efficiencies against electrical costs and heat pump efficiencies, in many regions of the United States, providing an average COP of 2.7 or better will provide operational costs below a natural gas-boiler. If adding on-site solar plus battery microgrids, often a project can end up with a levelized cost of energy below the utility, lowering the required COP to hit cost parity with natural gas.
Heat pump emissions
In addition to driving exceptional efficiency, design engineers need to understand their local electrical grid emissions profiles to make sure their designs are indeed resulting in reduced operating emissions. Each electric independent service operator in the country has a unique blend of sources for their electricity. Some ISOs rely heavily on burning coal or natural gas in their power plants, resulting in higher emissions profiles, while other ISOs have large portfolio of noncarbon producing and renewable energy sources such as solar, wind and nuclear, which result in much lower emissions per megawatt hour of electricity produced. With many states and ISOs having polices in place to drive a deeper adoption of renewable energy into their grid mix,
resources such as the National Renewable Energy Lab’s cambium can be used to look at long term projections for each ISO’s emissions.
Long-run marginal emissions factors are useful for understanding the impact of heat pump designs in the long term (future decades), but for understanding the emissions impacts of switching to a heat pump based system down to the hourly impact, short-term marginal emissions rates are much more useful. Short-term marginal emission rates take into account which types of source energy would be brought online on the grid to meet the added electrical demand from an all-electric heat pump system on an hour-by-hour basis.
Each ISO has different short term marginal emissions rates for each hour of the year, depending on how dirty their peaker plants are, how much excess renewable power they have available, etc. There are many factors that influence these shortterm marginal emissions factors. As the actual emissions of an ASHP based heating system are heavily dependent on OAT as well as which grid it is connected to, it’s valuable to review the project location against available data sets.
As each ISO has very different source energy mixes, peaker plant operations and renewable energy depth in their energy portfolio, the short-term marginal emissions rates vary widely across the United States. In addition, even within a single ISO, the emissions rates can vary widely within a single day or between months in the year. This is especially true for states like California, which have very large intermittent renewable energy from solar.
Visualizing short-term marginal emissions rates can also help design teams augment their heat pump based systems to further reduce operating emissions. Where ISOs have significant low-carbon energy sources, thermal energy storage can be deployed to shift operating loads into those hours with the lowest carbon footprint. In California that may mean shifting heating hot water production to midday hours when solar energy is abundant on the grid. For Chicago that may mean shifting heating hot water production to early morning hours, when nuclear base load is underused.
It is always important to keep in mind long-run marginal emissions rates as well. As an example, although central Iowa’s short-term marginal emissions rates may seem higher, significant amounts
FIGURE 8: Short-term marginal emissions rates for independent service operators serving San Francisco, New York City, Chicago and Des Moines. Data courtesy of Wattime. Courtesy: SmithGroup
of wind energy are being added to the grid in that region each year. If combined with electric battery storage, short-term marginal emissions rates could be reduced significantly.
Once the appropriate heat pump has been selected for the project’s climate zone and load profile, an efficient supply water temperature regime has been selected and the appropriate emissions factors have been accounted for, the engineering team can compare total emissions performance against a baseline natural gas boiler system. Each jurisdiction that has implemented building performance standards for existing buildings may have a different baseline to compare against. With the forthcoming alignment of standards, especially with ASHRAE leadership, the differences between jurisdictions should be minimized.
With the national push to reign in greenhouse gas emissions and move to decarbonize the economy, heat pumps provide a valuable enabling system to that end. When designing heat pump-based systems, carefully considering heat pump selection, refrigerant selection, the supply water temperature regime and opportunities to align with low-carbon hours on the grid provide the design engineer several strategies to dramatically increase efficiency while reducing emissions at the same time. cse
Stet Sanborn, AIA NCARB CPHC, is a principal, licensed architect and the mechanical engineering discipline leader for SmithGroup’s San Francisco office, where he leads decarbonization efforts and the design of cost-effective net zero carbon buildings.
csemag.com
Heat pumps
• All-electric HVAC systems like heat pumps can help reduce carbon emissions and increase energy efficiency.
• Both new and existing buildings can improve sustainability by introducing systems like heat pump hydronic systems.
BUILDING SOLUTIONS UILDING
By Joshua Hunter, PE, CDM Smith, Orlando, Florida
Specifying low-voltage variable frequency drives
Understanding different types of low-voltage VFDs and how to specify them is an important ability for electrical engineers
When it comes to starting and running industrial motors, such as blowers or compressors, there are several options available, including but not limited to, across-the-line starting with a motor circuit protector, reduced voltage auto-transformers, reduced voltage soft starters and variable frequency drives. The across-the-line option is the cheapest but is not recommended for larger motors as in-rush currents will be largest with this starting method, often six to eight times the motor’s normal operating current. This can create a need for oversized electrical equipment, which will typically cost more than the savings from the starter.
An RVAT, RVSS and VFD can all be used to reduce the in-rush currents created by a motor during startup. While the RVAT and RVSS are similar in cost, the VFD can be five to 10 times more expensive than these other two options depending on the type of VFD chosen.
However, the increased cost comes with some additional benefits and capabilities:
• Improved power factor — achieved with the use of direct current bus capacitors within the VFD. This is because the dc bus capacitors provide the needed reactive current to the motor, required to induce the rotor’s magnetic field and the input supply line only has to be real power with the voltage and current almost perfectly in phase. The benefits of improving power factor include avoid-
ing power factor penalties from the utility, reducing demand charges from the utility and reducing the current carried by the distribution network.
• Extended motor life — caused by controlling motor current, moderating start and stop functions and reducing the wear and tear on the motor. This can lead to reduced replacement costs by reducing how often a motor needs to be started and stopped and providing a smoother transition. However, long VFD motor feeder lengths can cause reflected waves and the slower shaft speed of the VFD can cause cooling issues for totally enclosed fan-cooled enclosures. These are potential issues which need to be addressed.
• Speed control — an ability for a VFD to produce a varied frequency, which can be used to control the speed of a motor based on its needed output. This can be done using open loop or closed loop control. For open loop control method, the volts/Hertz output to the motor is controlled independent of feedback from the motor. This can be done using linear or custom nonlinear output curves. To ensure the VFD is providing accurate speed control, there is a tuning mode, which can be used to compensate as needed. For the closed loop control method, the VFD will monitor the voltage and current of the motor via the power leads and determine the motor speed. This allows the VFD to vary the output voltage and current to achieve the required torque and desired speed. Each control method is useful for different types of motors and provide a useful tool for applications that require precise or varied motor speeds.
• Reduced energy consumption — lowered by reducing load demands for motors, which do not
FIGURE 1: A 25-horsepower 6-pulse variable frequency drive installed at a wastewater treatment plant. Courtesy: CDM Smith
need to run at 100%. This benefit is often the most important and provides more cost savings than may be first thought. This is because of how affinity laws work for centrifugal pumps. These affinity laws express mathematical relationships between variables involved in pump performance and are useful for predicting the effect of speed on pump performance. Based on the affinity laws, a 50% reduction in rotational speed will reduce the power used to 12.5%. Even a pump rotational speed of 90% will reduce the power required to 73% and a pump rotational speed of 75% will reduce the power required to 42%. This means small reductions in speed can provide major energy savings potential.
‘ To ensure the VFD is providing accurate speed control, there is a tuning mode, which can be used to compensate as needed. ’
Often, these advantages are enough to outweigh the additional upfront cost of the unit, especially when speed control is a necessity.
When choosing a VFD, there are some additional considerations, which must be made that could otherwise be cause for concern. The following are some of the major items to consider:
• Harmonics — deviation of the ac power sinusoidal wave form caused by a nonlinear load, resulting in the flow of harmonic currents in the ac power system. This harmonic distortion has effects on both linear and nonlinear loads, as well as propagating through the utility source and affecting other users. The harmonics can cause capacitor banks to fail, trip circuit breakers, burn out motor windings and cause transformer overheating. For these reasons, it is important to consider mitigations to curtail harmonic distortion. This can involve choosing the appropriate VFD to specify or installing external harmonic correction units. It is recommended for the design engineer or other involved parties to perform a harmonic study to ensure harmonics are being properly mitigated. An important reference for harmonic control is the IEEE-519 Recommended Practices and Requirements for Harmonic Control in Electric Power Systems standard, which focuses on pre-
venting one utility customer from causing harmonic problems for another utility customer or the utility itself.
• Reflected waves — over-voltages caused by the quick switching of insulated gate bipolar transistors used in modern VFDs. When not mitigated, these reflected waves put stress on cable insulation, motor insulation and the motor windings. This ultimately causes damage and reduces the life of the equipment. This damage happens because the reflected waves create peak voltages higher than what the motor and motor leads are rated for. Some options for mitigating reflected waves include the following:
• Specifying inverter duty motors, which are capable of withstanding higher peak voltages. Inverter duty motors withstand higher peak
• Learn the purpose and advantages of variable frequency drives.
• Understanding major design considerations when choosing to use variable frequency drives.
• Knowledge of common types of variable frequency drives.
FIGURE 3: A standard active front end circuit diagram. Courtesy: CDM Smith
FIGURE 2: A standard 6-pulse circuit diagram. Courtesy: CDM Smith
BUILDING SOLUTIONS UILDING
voltages by using voltage spike-resistant insulation systems, which may include inverter-grade magnet wire, improved insulation and low heat rise designs. These improvements allow an inverter duty motor to withstand an upper limit of 3.1 times the motor’s rated line-to-line voltage, per National Electrical Manufacturers Association MG 1 Part 31. For a motor rated at 460 V, this comes out to a peak voltage of 1,426 V.
cost, it is not recommended to use this filter unless the VFD is located about 2,000 feet away or more
• Limiting the distance between the VFD and motor. By limiting the distance between the VFD and motor, costs can be saved by not having to purchase ever increasingly more expensive filters, not to mention the costs saved from the length of cables as well as the increased size of cables required due to voltage drop.
• Electromagnetic interference — electrical signals, also known as “noise,” caused by multiple drives located in an area. These electrical signals can appear in control systems and produce undesirable effects in the system, such as communication errors, reduced equipment performance and malfunctioning or nonoperating equipment. Mitigation measures include installing EMI filters, ensuring a low impedance ground system, installing VFD shielded cable or installing a common mode choke.
csemag.com
Variable frequency drives
u With proper consideration, a VFD can provide an efficient method for controlling a motor's speed, lower electricity costs and reduce the inrush currents that accompany a motor as it is first energized.
u This article focuses on advantages and major design considerations when specifying a VFD, accounting for cost, efficiency and harmonic distortion. Information about the common types of VFDs is also included.
• Specifying the VFD to be equipped with a load reactor to provide a buffer between the motor and VFD. The load reactor can reduce the effect of reflected waves and increase load inductance. The load reactor is recommended for noninverter duty motors greater than 100 feet away from the VFD or inverter duty motors greater than 300 feet away from the VFD. The load reactor should be placed as close to the VFD output as possible to be effective and will typically protect the motor about 500 feet away from the VFD.
• Installing dv/dt output filters to limit the peak voltage. Dv/dt filters work by changing the voltage rise time and slowing pulse width modulation pulse transitions. These filters provide longer range motor protection compared to load reactors, up to about 2,000 feet away. It is recommended to install a dv/dt output filter when the VFD and motor are over 500 feet from each other.
• Installing a sinewave filter to convert the rectangular PWM output signal into a smooth sine wave voltage, thereby removing the voltage spikes. Because this filter works by creating a sinewave, there is not limiting distance. Due to the increased
• Heat loss — considerable amounts of heat are generated from multiple parts of the VFD process during power conversion from alternating current to dc and dc to ac. The VFD switching frequency can be lowered to reduce heat generation in the drive but lowering the frequency will increase the creation of harmonics and the audible noise heard from the motor. The primary method for preventing overheating of the equipment is using heat sinks and fans to dissipate the heat through vents in the enclosure. If possible, it is ideal to place VFDs inside a climate controlled electrical building or room. However, there are multiple vendors that can provide external VFDs with an air conditioning unit. The HVAC system will need to account for the added heat generation as VFDs can quickly raise the indoor ambient temperature. It is best to reach out to VFD manufacturers to determine the expected heat generation.
Common types of variable frequency drives
A VFD is used to control the speed of inverter duty ac motors. It consists of a rectifier, dc bus and inverter. The rectifier converts the ac power to dc power. The dc bus smooths out the dc power by using an inductor capacitor filter and the inverter converts the dc bus to a simulated, pulse-width modulated, sine wave using IGBTs, which switch on and off. While the inverter and dc bus portions
FIGURE 4: This shows three 150 horsepower variable frequency drives within NEMA 3R enclosures. Courtesy: CDM Smith
‘ Many manufacturers have created new techniques using autotransformers to achieve the required phase displacements. ’
of a VFD remain the same, the rectifier portion depends on whether a multi pulse or active front end drive is selected.
6-, 12- and 18-pulse drives
The cheapest and simplest VFD is a 6-pulse VFD, which uses a three-phase full-wave diode bridge, consisting of six rectifier devices, from which it gets its name (see Figure 2). The downside to this configuration is that the current draw at each diode bridge is not uniform and when the supply is not perfectly balanced the drive will produce harmonics. While this may not be a problem for smaller motors, it can be a concern for larger motors, especially when the amount of total load on the VFD increases.
To reduce harmonics, a 6-pulse drive can be upgraded to a 12- or 18-pulse drive. This is done by using 12 rectifier devices or 18 rectifier devices, effectively paralleling the 6-pulse drive rectifiers two or three times, respectively.
However, these configurations require an added transformer connected to the beginning of the circuit. This transformer consists of a primary side winding with two secondary windings each phase shifted 30 degrees apart for a 12-pulse drive and with three secondary windings each phase shifted 20 degrees apart for an 18-pulse drive. These transformers are necessary to create phase shifts, which help to displace the harmonics currents, so they cancel each other out.
The 30-degree phase shift from the 12-pulse drive cancels out the 5th and 7th harmonic currents, while the 20 degree phase shift from the 18-pulse drive additionally cancels out the 11th and 13th harmonic currents.
Many manufacturers have created new techniques using autotransformers to achieve the
However, the addition of this extra component along with the extra rectifiers and convertors adds extra cost, increases the size of the units and generates more heat.
Due to these disadvantages, it is often more beneficial to only use 6-pulse drives for smaller motors, 100 horsepower or less and switch to either 18-pulse drives or alternatively the more modern AFE drives for larger motors. It is not recommended to ever use 12-pulse drives as they cost approximately the same as an 18-pulse drive, has less benefits than an 18-pulse drive and many manufacturers no longer make them. Many manufacturers make 24-, 36- and 54-pulse drives, but these are for much larger motors, up to 10,000 horsepower, that are often medium voltage.
Active front end drives
AFE drives are an alternative to multipulse drives, especially for 12- and 18-pulse drives, which are more expensive, less efficient, take up more space and are worse at mitigating harmonics. Instead of having a passive rectifier section consisting of
required phase displacements.
FIGURE 5: Technicians work inside one of the 150 horsepower variable frequency drive enclosures. Courtesy: CDM Smith
BUILDING SOLUTIONS UILDING
‘
When a drive has built-in regenerative capabilities, the motor can be rapidly stopped and reuse the excess power without the need for extra heat dissipation.
multiple diodes and a transformer, the AFE drive uses an active rectifier section using IGBTs, similar to the inverter section of multipulse drives (see Figure 3).
The advantage this provides is that the IGBTs switching on and off can draw a nearly perfectly balanced power supply for the drive by filtering out harmonics generated by the VFD at any given moment. This is done by creating harmonics that cancel out and effectively eliminate the harmonics that would be created by a standard 6-pulse drive. The end result is an efficient ac output with minimal harmonic distortion.
An additional advantage of AFE VFDs is the ability to regenerate energy back to the utility source or other system loads. This regeneration happens during the motor braking process, which is the period of time when the motor has been shut off. Normally, when a motor is suddenly shut off
the excess energy becomes unwanted heat, requiring braking resistors and cooling equipment to dissipate this heat and prevent damage to the motor.
When a drive has built-in regenerative capabilities, the motor can be rapidly stopped and reuse the excess power without the need for extra heat dissipation. The excess power will be sent back to the utility grid or used to power other facility equipment. This can be especially useful for applications that require high-inertia loads, such as cranes and hoists that require frequent braking.
If the motor load makes up a large portion of the facility demand and the facility is disconnected from the utility, the motor generating power could create a voltage spike, tripping circuit breakers. To mitigation this issue a battery or capacity bank could be installed to absorb the excess power generated. cse
Joshua Hunter, PE, is an electrical engineer at CDM Smith, focusing on the design and analysis of electrical power systems.
Assembly occupancy fires that wrote NFPA 101
Learn about some of the historic fires that helped formulate NFPA 101: Life Safety Code
In jurisdictions across the United States and even internationally, the adoption of NFPA 101: Life Safety Code defines the minimum standards required in buildings to protect occupants in the event of a fire. The code includes a robust chapter on assembly occupancies, which are typically characterized by a higher occupant density than other types of occupancies. Many of those requirements originated similarly in response to horrific fires that occurred in these occupancies, highlighting the need for improved life safety.
Assembly occupancies present a unique challenge in fire protection and life safety with their high occupant loads and occupant densities. They often have occupants that are not familiar with the
entire building layout and exit locations. They often have events where lights may be dimmed, alcohol may be served and occupants may be impaired.
In some cases, the facility may be used for different types of events that change the landscape of risk from one day to the next. Unfortunately, one of the best ways to learn how to protect these highoccupancy facilities is to study what went wrong in the past when they had fires and improve design to mitigate those issues.
We will cover some of the historic fires and the code requirements they inspired that still exist in NFPA 101.
Life safety in Cocoanut Grove
One of the most well-known assembly fires in U.S. history was the Cocoanut Grove Restaurant and Supper Club in Boston. The building located at 17 Piedmont Street was a single-story building with a basement and a very popular hangout spot during the 1930s and early ‘40s. The club’s basement contained a bar called the Melody Lounge along with kitchens, freezers and and storage areas. The main dining room above occupied the first floor along with a ballroom, bandstand and several additional bar areas.
On Nov. 28, 1942, the Cocoanut Grove was packed. In the Melody Lounge, a busser attempted to replace a light bulb located inside an artificial palm tree and used a lighter to see what he was doing. Moments later patrons noticed a fire in the palm tree that rapidly spread across the Melody Lounge, fueled by the flammable décor. Customers began streaming for the basement’s only public
April Musser, PE, CDM Smith, Atlanta
FIGURE 1: An illuminated emergency exit sign. Courtesy: CDM Smith
Objectives Learningu
• Understand the unique challenges and constantly changing risk landscape associated with high-density assembly occupancies such as bars and nightclubs.
• Review contributing factors in three assembly fires and how the codes changed to prevent similar incidents in the future.
• Learn about the intent behind NFPA 101: Life Safety Code and other codes for assembly occupancies.
exit, a single 4-foot-wide set of stairs that led to the foyer on the first floor.
However, the fire quickly traversed the ceiling of the Melody Lounge and moved up the stairs into the lobby where frantic patrons were attempting to escape. The main entrance was a revolving door and as people rushed to exit, the door became jammed with people crushed against it by the rush. Sadly, 492 people perished that night because of the fire.
The lighting — and lack thereof — was an issue from the start and the occupants who were able to locate alternative exits found that the doors swung inward. This caused people to crush against them making it impossible to pull them open.
As a result, NFPA 101 now requires emergency exit doors to swing in the direction of egress for assembly occupancies and requires illuminated emergency exit signs to help patrons find exits even when the power fails. Fire sprinkler protection requirements for assembly occupancies meeting certain occupant load thresholds were also added.
More importantly, the first edition of NFPA’s Building Exits Code, which was written 15 years before the fire, gained traction as U.S. cities adopted it and codified it into law. In its current iteration as today’s NFPA 101, it still has requirements for revolving doors to have swinging doors adjacent to them and for the revolving doors to have collapsible wings to prevent the bottlenecking that occurred at the revolving door of the Cocoanut Grove.
Beverly Hills Supper Club
On Saturday, May 28, 1977, the Beverly Hills Supper Club in Southgate, Kentucky, was crowded with more than 2,000 patrons when a fire broke out. The official cause of the fire was determined to be electrical in nature. The building did not have sprinkler protection and the fire spread rapidly throughout the sprawling facility that covered over 65,000 square feet across its 19 rooms on two floors.
This facility had undergone multiple renovations and additions over its lifetime, but these renova-
tions never included the addition of a fire alarm or automatic sprinkler system. The only fire protection equipment available were portable fire extinguishers. When staff noticed a fire in one of the smaller party rooms, they immediately notified management.
However, with no fire alarm system, there was no means of detection or effective way to notify everyone in the numerous meeting rooms, party rooms, bars and the overcrowded Cabaret Room where a musical performance was about to begin. Staff began notifying patrons to leave in the various bars and party rooms as they became aware of the fire.
However, it is estimated that it took 20 minutes before an employee in the Cabaret Room learned of the fire and interrupted the performance to notify occupants to evacuate.
At capacity, the more than 1,000 occupants of the Cabaret Room had access to three separate exits. However, due to the lost time in notifying the guests, two exits quickly became blocked by smoke and flames forcing the entire mass of people to a single exit. Of the fire’s 164 fatalities, 99 were in the Cabaret Room. The entire complex was destroyed by the fire and the more than 500 firefighters that responded didn’t succeed in completely extinguishing the blaze until the following Monday, May 30, 1977.
Several factors contributed to the severity of the fire and the high loss of life. Once again, combustible décor was identified as a contributing factor was along with inadequate egress in the Cabaret Room, the absence of a fire alarm system and the absence of a fire sprinkler system. Regarding the
ing door with adjacent swinging doors as well as collapsible fins inside the door as now required by code.
csemag.com u
Assembly occupancy
• Several fires at locations with high occupancy or poor life safety systems helped create NFPA 101: Life Safety Code.
• Assembly occupancies are characterized by a higher density of people than other types of occupancies, and must conform to strict standards.
FIGURE 2: A modern revolv-
Courtesy: CDM Smith
BUILDING SOLUTIONS UILDING
issue of inadequate egress, the code officials had noted this in plan reviews, but had allowed the club owner to obtain the certificate of occupancy before the deficiencies in egress were rectified.
Once the club became operational, the owner never did correct those deficiencies. One of the noted egress issues was that there were not enough exits in the Cabaret Room, where most of the victims were found.
As a result of this fire, the following edition of NFPA 101 included several changes. Both new and existing assembly occupancies with occupant loads exceeding 300 were required to have a fire alarm system with voice messages for occupant notification. In addition, new assembly occupancies with occupant loads exceeding 300, regardless of the building construction type, were required for the first time to be protected with an automatic fire
sprinkler system (with some specific exemptions to the requirements).
The Station Nightclub
On Feb. 21, 2004, a horrific scene unfolded in West Warwick, Rhode Island. The Station Nightclub had lived many lives as a restaurant, nightclub, pub and tavern. At the time of the fire, the facility was used as a nightclub and was hosting a Great White concert in the club area, which was separate from the bar area.
The building had a fire alarm system but did not have an automatic sprinkler system. Egress from the facility included a main entrance served by a 6-foot-wide corridor with openings into the bar and the club area. This entry corridor created an egress pinch point at the main entrance. Additional exits were available adjacent to the stage in the club and adjacent to the horseshoe-shaped main bar area. A final exit was available from the kitchen. Due to noise complaints, insulating expanded foam material had been applied to the club’s interior walls around the drummer’s alcove and throughout the raised stage area. It is not known how far into the club the insulation extended.
During the band’s performance, pyrotechnic devices called gerbs (which deliver a stream of sparks) were activated on the stage. They ignited the foam insulation that was used as interior finish to dampen the noise. The fire grew rapidly and the main entrance corridor became choked with people. As people collapsed in the main entrance, patrons began piling up on top of and behind people that had collapsed in the passageway from the heat and toxic smoke that filled the facility. Ultimately, the fire’s death toll would land at 100 people.
While NFPA 101 had already included requirements for interior finishes, they were not enforced in this building. This is one of the contributing factors of the fire and large death toll. However, due to this fire, NFPA 101 was updated with new requirements for egress, sprinklers and the use of indoor pyrotechnics. The most notable code change was the requirement for mandatory sprinklers in Group A-2 occupancies where the occupant load is 100 or more (it was previously 300 or more).
As noted above, a new section was added to NFPA 101 restricting the use of open flames and pyrotechnics in assembly occupancies without the
FIGURE 3: A performer onstage including crowd view of an assembly occupancy hosting a live music event. Courtesy: CDM Smith
approval of the authority having jurisdiction. This approval would ensure that satisfactory precautions have been taken and the pyrotechnics comply with NFPA 1126: Standard for the Use of Pyrotechnics before a Proximate Audience.
Ultimately, the biggest change to NFPA 101 following the Station Nightclub fire were the requirements for the main entrance/exit width. Previously, the main entrance and exits were required to accommodate 50% of the building occupancy for this type of assembly. The changes increased the required width of the main entrance/exit to accommodate at least two-thirds of the total occupant load for bars with live entertainment, dance halls, discotheques, nightclubs and assembly occupancies with festival seating.
In addition, the other exits were required to accommodate at least half of the building occupancy. Therefore, for these types of assembly occupancies, the total egress capacity is required to be more than 100% of the occupant load.
In conclusion, tragedy can be a very harsh teacher. The unique risks related to high occupant
‘ For these types of assembly occupancies, the total egress capacity is required to be more than 100% of the occupant load. ’
loads and the constantly changing risk landscape of assembly occupancies require that we remember these hard lessons as we apply and enforce the requirements of NFPA 101. To protect occupants in these types of assemblies, all components of active and passive fire protection must be in place. This includes design of adequate and compliant egress systems, interior finish classifications, automatic sprinkler protection and fire alarm systems with detection and occupant notification.
These requirements in NFPA 101 ensure that we take these lessons with us into the future for assembly occupancy design and construction. cse
April Musser, PE, is a fire protection engineer with CDM Smith and has more than 20 years of industry experience in fire protection and life safety.
Your space is like no other. How you light it should be just as unique. Universal Douglas is one of the only commercial lighting manufacturers that carries both modern LED fixtures and smart, cyber-secure controls under one roof, giving us the flexibility to create custom, on-spec solutions for any footprint. Plus, we’ll work with you every step of the way to seamlessly integrate your entire lighting system, effectively transforming your space, increasing your energy savings and giving you more control than any cookie-cutter fix ever could.
The voice of the engineering community speaks loud and clear in the following pages featuring the corporate profiles for companies participating in the 2023 Executive Voice program. We offer our sincere thanks to these advertisers:
Air distribution products such as grilles, registers, diffusers (GRDs) and air terminal units (ATUs) control the volume and pattern of airflow into and out of a space to provide occupant comfort. However, in healthcare buildings, laboratories, and cleanrooms, air distribution products contribute to occupant safety and health in addition to comfort ventilation. These critical environments have prescriptive air change requirements that are significantly higher than typical building requirements. As a result, design engineers need to be aware of the airflow patterns and where they are being directed to ensure patient and occupant safety.
Greenheck’s new line of healthcare, laboratory, and cleanroom (HLC) air distribution products are designed, engineered, and tested to meet or exceed today’s critical environment
standards for performance and energy efficiency. These products include:
Laminar Flow Diffusers — engineered to provide a vertical projection of low-velocity supply air. The laminar flow diffuser introduces clean supply air without the entrainment of airborne particulate in the space due to its low velocity. These diffusers play a critical role in maintaining an aseptic environment below the diffusers in operating rooms, patient isolation rooms, pharmacies, and cleanrooms.
Radial Flow Diffusers — an effective method of air distribution for laboratory and patient isolation room applications where a high volume of air is required. The specialized air pattern design produces a uniform pattern with a very short throw that does not interfere with fume hood operation.
Operating Room Systems — custom designed and precisely fabricated to accommodate the specialized medical, mechanical, and electrical considerations of operating room environments. These modular diffuser systems can be linked together in virtually any combination to sufficiently cover the needed surgical area, producing one large laminar mass that flows over and blankets the operating room table, helping to protect and effectively isolate the patient from contaminated air.
Matthew McLaurin
Greenheck
Segment Mgr.— Healthcare, Laboratory, and Cleanroom Air
Distribution
“Design engineers need to be aware of the airflow patterns and where they are being directed to ensure patient and occupant safety.”
Greenheck healthcare, laboratory, and cleanroom products are configured to order, meeting unique application requirements, and are factory-tested to meet Institute of Environmental Sciences and Technology (IEST) test standards to ensure products perform as specified in these controlled environments.
For more information on these products along with Greenheck’s entire line of air distribution products, click here or scan the QR code at left.
HLC-SPA Structural Modular Plenum Array is a complete diffuser turnkey system.
Every engineered pipe system needs to compensate for noise, vibration, movement, and piping alignment. The Metraflex Company has the products you need to protect your piping and make it more efficient.
Expertly Engineered Products
Vibration isolation. Noise dampening. Thermal expansion and contraction. Pipe alignment and seismic movement. Pump connections and flow conditioning.
The Metraflex Company has been supplying piping specialty products to the commercial HVAC industry since 1958, with production located in Chicago, IL. Manufacturers of the innovative Metraloop® expansion loop for thermal expansion and seismic movement, the completely re-designed, energy-efficient LPD Y-Strainer, and the Suction Diffuser Flex and VaneFlex™ flow conditioning joints, The Metraflex Company makes a variety of engineered piping products including expansion joints, expansion compensators, wall penetration seals, pipe guides, pump connectors, strainers, valves and more.
Delegated Design Services
The Metraflex Company is eager to assist you on any application. Need help designing an engineered piping system? Contact Metraflex. We offer delegated design services for firms needing this special expertise.
Increasingly project specifications are calling for a “delegated design submittal” and making the contractor responsible for the design of piping expansion. Metraflex uses CAEPipe® finite element analysis software to analyze your complex piping layouts for movement, stresses and anchor loads. You receive all the materials and calculations required for you to meet submittal requirements.
The Best Reps in the Business
The Metraflex Company has representatives across the country and around the world with the expertise to help you with your application or installation. In addition, our technical support staff can help you with special applications, tailoring our line of products to your specific needs.
For the products you need to protect your piping and optimize efficiency contact Metraflex today!
Metraflex production facility in Chicago. IL
Jim Clauss President, Metraflex
Every good car owner knows that it is important to ensure your vehicle is properly maintained and to promptly address dashboard lights. The same care should apply to a steam system, one of the most critical processes in a facility, for continued safety, efficiency and reliability.
At Miura – the manufacturer of modular, on-demand steam systems — we’ve spent the past 30 years focusing on the importance of predictive and preventative maintenance to help our customers get the most out of their boiler investment. To do this, we’ve developed intuitive monitoring systems and sensors to help customers easily stay in the know with all connected boiler room equipment.
First, we introduced Miura Online Maintenance (MOM) to help customers better monitor equipment and connect with our in-house experts to troubleshoot issues. After continuous research and development, we launched the Miura Connect remote monitoring platform in 2021 to allow operators to access trending data from any smart device.
We know that maintenance matters, but recognize that it may be easily overlooked until a larger problem arises. That’s why utilizing intuitive monitoring and easy-to-use interfaces on the boilers to preventatively care for a Miura system ensures numerous advantages.
• Continuous Reliability: A well-maintained boiler with critical components monitoring ensures a like-new operation with consistently high-quality steam.
VP of Customer Experience & Maintenance Operations
• Trend Forecasting & Predictability: Monitoring systems can pull trends and predict when maintenance or inspection is needed for better planning.
• Maximum Uptime & Productivity: Online monitoring signals a quick expert response to help avoid downtime and production losses, while modular boiler systems allow for uninterrupted production.
Just like you would care for your vehicle, staying ahead of problems with early issue detection and trends is the best way to ensure the critical steam investment maintains its maximum lifecycle. Partnering with Miura to provide both modular steam systems and innovative monitoring technologies provides quality steam for years to come.
For more information or to talk with a steam expert to learn more, visit us at miuraboiler.com or email us.info@miuraz.com.
Noritz has been developing and manufacturing the finest gas-operated water heating products in the world since 1951, when it was founded in Japan. Today, the company is the number one global manufacturer for tankless technology. Increased environmental awareness, with the conservation of energy and space worldwide, has encouraged Noritz to expand across the globe.
The Noritz Commercial line is the most precise and efficient method of heating water for any commercial project, offering the following advantages for engineers:
• Modularity: The Noritz modular system is based on a single self-contained, interchangeable unit that can combine and communicate with like units to meet any hot water demand.
• Multi-System Capability: Up to 24 Noritz units can be linked together with a single system controller. This allows outputs of 9.1 million Btuh and 316 gallons per minute.
• Modulation: Noritz fully modulating technology tracks and meets any hot-water demand with pinpoint accuracy, matching energy consumption to present requirements.
• Intelligent Performance: In a multi-system setup, the Noritz commercial units will communicate with one another and work in unison to even out the load on each individual unit, maximizing output and system life.
• Redundancy: If, in a multi-system setup, one unit happens to go offline and needs to be serviced, the remaining units will split the BTU demand to maintain set point temperature.
The latest Noritz commercial product to incorporate these advantages is the NCC199CDV condensing tankless water heater, approved for common-venting up to six units in commercial applications. With a 98-percent thermal efficiency, the unit is both Commercial ENERGY STAR® and AHRI-certified. Up to 24 of these units can be linked together using a Multi-Unit System Controller. The resulting, modular system would offer a BTU input range from 18,000 to 4.8 million, yielding a turndown ratio of 266:1.
Jay Hassel President & COO, Noritz America Corp.
In addition, flexible venting options allow for vertical or horizontal termination with PVC, CPVC, or PP venting. The unit can vent up to 60 feet with 2-inch vent piping; and 100 feet with 3-inch materials. The premix, fully modulating burner has a nitrogen-oxide emissions level of only 14 parts per million (ppm), far exceeding the South Coast Air Quality Management District requirement of 20 ppm.
The NCC199CDV is built to last, manufactured with 316L grade stainless steel for high durability and corrosion resistance. It represents the latest and best that the Noritz Commercial line has to offer.
For more information on the NCC199CDV and the Noritz Commercial line, please call 1-866-766-7489 or visit www.noritz.com/commercial.
CSE: What’s the biggest trend you see in office buildings?
Miles Brugh: With people more aware of their time and specifically the time they spend getting to the office, we are seeing employers and buildings allocating more resources to improving their spaces. For employers, we are seeing them provide more flexible and comfortable spaces, increased collaboration space and improved technology, which all support the many changes that companies have seen over the past couple of years. For the buildings themselves, we are starting to see some movement on the building-provided amenity space including lobby improvements and added seating areas to provide users with alternative work locations. For new office buildings under construction, we are seeing these amenity spaces receiving much more time and attentional to provide an improved experience within these buildings.
Adrian Gray: Environmental and net zero carbon legislation. Many U.S. cites are applying legislation to policies that are already in place in Europe, with fines for noncompliance that increase at various gateways. This has been a driver for
change in European cites as the road to net zero has been explored for more than two decades. In many cities in Europe for example, the allowable energy criteria have reduced to the extent that the standard practices for air conditioning solutions is no longer permitted. Mixed-mode and natural ventilation are now considered across most city center locations.
Matt Humphries: A key trend for clients is to build for the long term. The goal might be to build a permanent piece of infrastructure to incorporate that isn’t thought of with an end date in mind, but as a permanent, ongoing part of their portfolio. Clients have a better appreciation of the full life cycle cost of buildings. As clients they have a view to the long-term for operating costs, but are also mindful of incorporating what we are finding works well. Geo-exchange, ground-source heating for example and minimizing combustion. In terms of sustainability, the bigger trend is the focus on carbon and future energy costs.
commissioning and similar programs that are often incentivized by utility company rebate programs.
CSE: What trends do you anticipate in the next year or two as hybrid work remains in flux?
Matt Humphries: The pandemic has created other drivers. A key driver is getting as much fresh air into buildings and keeping the air as clean as possible. Of course, it is true that developing mechanical systems that provide the healthiest air at lower energy costs is a “battle” against two different outcomes. Strategies we used include energy recovery on exhaust and filtration/treatment to reduce pathogen concentration in the airstream.
Miles Brugh: I expect that employers will continue to experiment with their spaces and move and adjust based on user feedback. Flexibility is going to be a larger priority in the decision making for projects so that the space is able to adapt to the changing workforce.
Office buildings
u Office building design is changing as owners and tenants expect more, especially flexibility.
u Electrification, outside air and high-tech buildings are new trends in office space.
John Yoon: Even a half-full building still needs to be properly conditioned. However, the load profile of most buildings typically doesn’t scale linearly with occupancy, resulting in unexpectedly high operational costs. As buildings continue to be half full while most tenants are still “work from home” or hybrid, I expect to see a continued emphasis on design solutions to minimize those operational costs — especially in existing buildings. The lowest hanging fruit seems to be retro-
Adrian Gray: Environmental, social and governance, or ESG, requirements of building occupiers is an increasing trend toward new and refurbished buildings to meet the latest sustainability benchmarks. This in turn is driving a program of comprehensive refurbishment of existing buildings as older properties become less desirable. In London all new major development projects have to take account of the embodied carbon required in demolition and construction.
John Yoon: The greatest trend is uncertainty. While it hasn’t reached the same levels as the Great Recession of 2007-2008, the parallels are uncanny. During the Great Recession, companies disappeared overnight, dramatically driving up vacancy rates and cratering commercial real estate valuations. While the job market has been unusually healthy while recovering from the great pandemic, the explosion of working remotely has caused office workers to disappear from the central business districts in most cities, leaving half-filled office buildings in their wake. It isn’t clear when or if those workers will come back.
CSE: What types of office building assessment programs are owners adding to ensure tenants are breathing healthy, clean air?
John Yoon: In direct response to COVID concerns, we’ve seen an increase in ASHRAE Standard 62.1: Ventilation for Acceptable Indoor Air Quality compliance study requests. However, recommendations for increased ventilation often have a downside in increased operational costs.
Adrian Gray: During the COVID-19 pandemic, many building owners invited mechanical, electrical and plumbing engi-
neering consultants to identify upgrades to existing systems to prevent and/or mitigate the spread of the virus amongst building occupants. Many of the recommendations followed industry trends to improve ventilation and increase the amount of fresh air.
Matt Humphries: Overall, they are committed to getting as much fresh air into building and keeping the air clean.
CSE: How are engineers designing office facilities to keep costs down while offering appealing features, complying with relevant codes and meeting client needs?
Matt Humphries: The digital twin concept allows engineers to develop a model that you can use to analyze your current situation and adapt the way your building is being operated. Efficiency is now especially important. Since the pandemic, offices are not occupied all the time and we can't make the same assumptions as before about the use of space and resources. We need to incorporate ways to know when lights are needed, for example, since knowing when a space is actually occupied can enable you to be more efficient.
John Yoon: Mention the importance of MEP systems to most building occu-
Miles Brugh, PE
Project Electrical Engineer/Manager
ESD
Chicago
Adrian Gray, C Eng, Eur Ing
Global Director -
Commercial and Real Estate Sector
HDR
London
Matt Humphries
Associate Principal
Arup
Toronto
John Yoon, PE, LEED AP Principal Engineer
McGuire Engineers Inc.
Chicago
pants, you’ll typically be greeted with a blank stare. When construction costs are fixed and they are given the choice between enhanced MEP system functionality and more tangible items, like nice furniture or fancy interior finishes, MEP typically loses. When that happens, the typical direction from the owner is to provide only basic code compliant systems. Conveniently, more stringent requirements associated with new energy conservation codes necessitate greater functionality anyway. cse
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