HIGH-PERFORMANCE HVAC New AC responses to old applications

Iam inevitably reminded that every building in Canada isn’t air conditioned through a phone call or email request for advice on providing cooling to spaces where traditional forced air, ducted packaged or spilt system air conditioning is not practical. These applications may be older homes with radiant systems or workspaces in factories without air conditioning.

Most recently, the migration out of urban areas has spurred interest in upgrading electric baseboard heater or other non-ducted heating systems in homes in rural areas. Also spurring interest in air conditioning alternatives is the use of cottages as summer offices.

HVAC contractors have access to and are likely familiar with the ductless mini-split air conditioning systems that much of the rest of the world has used to air condition buildings for decades. Indeed, this technology is now so prevalent across Canada, it might seem there is little to “write home” about but there are some important opportunities and considerations when applying the inverter or variable compressor capabilities inherent to the mini-split technology.

The availability of variable speed, mini-split cooling systems with a range of indoor unit sizes and configurations allows professional contractors to provide more responsive and effective cooling options to houses without forced air ductwork than ever before. Indeed, mini-split technology may do a better job of meeting client’s expectations for quick response cooling than whole home centrally ducted systems. Be sure to research and specify equipment that can provide the critical dehumidification function and meet expectations for smart control interfaces.

Gord Cooke Gord Cooke Gord is a professional engineer who has spent 20 years helping builders and HVAC contractors implement innovative technologies into high-performance homes. He has particular expertise in IAQ and airflow management in houses, and can be contacted at gordc@buildingknowledge.ca.

The question of sizing air conditioning in a house without central forced air ducting presents a liberating opportunity. Recall that 40 per cent to 60 per cent of air conditioning loads in most houses is associated with the solar gain through unshaded windows and another 25 per cent is a function of internal loads, that is people and their activities, lights and appliances. Unlike in buildings with existing air handlers and ductwork where you have to think about the airflow capacity, in non-forced air applications the focus can be on targeting specific loads. Consider the orientation of the house and how that might relate to specific rooms that are commonly used in the afternoon and evenings. Ask your clients about the daily activities of their household as you consider the size and location of a mini-split air conditioner. For example, consider a family room where the five occupants gather to watch television and do homework on a computer. If that family room had west facing windows with a glazing area of seven square meters (75 square feet) that would result in a potential solar gain of approximately 1,400 watts (4,770 BTU/H) through unshaded, clear double-glazed windows. Add the heat gain of the five people (70 watts per person), the computer and the television (150 watts each) and the total heat gain during that peak period could be as much as 2,200 watts (7500 BTU/H) for that one room.

A mini-split air conditioner targeted specifically to this room, indeed for a specific time of day, would be so meaningful to your client and liberating for you to just have to satisfy that one specific, but critical, load. The added value of the inverter technology is the capability it provides for variable cooling capacity, allowing the system to match the intermittent nature of loads such as solar gain and variable occupancy. Follow the sun and the people around the building to determine size and location of cooling equipment. The inverter technology, in at least the top-tier brands, lends itself to multiple cooling heads with one outdoor variable condenser unit. The leading manufacturers now have a variety of indoor unit configurations to match building needs. Targeting that family room with one wall-mounted indoor unit and perhaps a cassette mounted in a ceiling space in the central hallway adjacent to bedrooms for night-time cooling. If space permits there are ducted versions that would allow two or three rooms to be serviced by a unit mounted in a closet with a return grille mounted on its face. Take advantage of the intermittent nature of cooling loads and the variable capacity of the mini-split systems to optimize initial and operating costs.

Another helpful attribute that you should include in all mini-split applications is specific control capabilities for a dehumidification cycle. While cooling loads are largely intermittent, humidity (latent) loads are quite consistent throughout the day in most buildings. Houses without central air conditioning have been prone to uncomfortable humidity levels unless a dehumidifier has been operated. Provide clients with mini-split systems with a control cycle option, often referred to as “dry” mode. In this mode, the fan speed of the indoor unit is reduced, while maintaining an appropriate compressor speed to avoid coil freeze up. This allows for enhanced dehumidification without over cooling spaces. Compare the performance specifications of the mini-split systems you are considering. The expectation should be a moisture removal capacity of at least two litres per hour per ton of cooling capacity (5 pints per hour) and ideally 4 l/h (3Pt/h) per ton of cooling capacity. Your client would program the indoor unit serving the bedrooms to run in the dehumidification cycle during the day, to maintain humidity levels below 50 per cent to 55 per cent and then switch to cooling mode just before bedtime for a more comfortable night’s sleep with optimized operational costs. Interestingly, the angst of oversizing central cooling systems that don’t dehumidify properly is avoided with mini-split systems. When applying one or more indoor units, it’s unlikely any one unit would overcool a home or building without removing appropriate amounts of moisture. Thus, one or more of the indoor units can be earmarked and controlled to run in dehumidification mode for as many hours of humid days as possible to optimize indoor humidity levels.

To meet the control expectations of your clients, such as those outlined above, you will want to help your clients choose a mini-split system that has the ability to be controlled remotely; a smart thermostat interface capability. Perhaps ironically, almost all mini-split units historically came with a handheld remote control, in addition to or in place of a wall-mounted thermostat.

While the focus of this conversation has been to add air conditioning capacity to homes without forced air heating, there is a reason to ensure the mini-split system specified is also a highperformance heat pump. Certainly, if the building you are adding air conditioning to is electrically heated, then the benefit of replacing as much of the electric resistance heating capacity with the more efficient air source heat pump function offered by mini-split systems is a must. In addition, there is a compelling initiative to replace fossil fuel heating appliances in homes and commercial buildings with heat pumps as part of Canada’s commitment to carbon reduction.

In areas where the electrical grid is considered green or clean, air source heat pumps have an important role to play in carbon reductions. Thus, if you are adding air conditioning to a building with a hot water radiant system, fuelled by oil, propane or even natural gas, be sure to choose a heat pump mini-split system rather than just an air conditioner. This gives your client the option of choosing to operate a low carbon heat source at some time in the future depending on fuel costs and availability. This is true even if the heat pump chosen doesn’t have the capacity to heat the entire building on the coldest of days.

Reducing the carbon footprint

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Testo Smart Probes come in a smart case for travel. Up to six Smart Probes can be operated wirelessly and simultaneously through a smartphone or tablet, with all measurement data transmitted directly to the free Testo Smart Probes App. www. ontor.ca testo.com

MagicPak All-In-One V-Series 2.5T HVAC Systems are self-contained heating and cooling packaged units that do not require outdoor units, line sets or separate venting. Available in EWC (electric heating and cooling) and HWC (gas heating/electric cooling) models, units offer a two-stage high-efficiency compressor, multi-speed blower motor for diverse airflow range, and an accessible control box with diagnostic LED and conventional 24V thermostat. The HWC offers AFUE ratings of up to 95 per cent. www. allied-commercial.com

The Briza 22 hydronic fan coil from Jaga Climate Systems is designed for spacesaving heating and cooling. Measuring 8.7-in. deep, it can be tucked into the wall or ceiling in a ducted or non-ducted installation. It can cover up to 27 ft. of horizontal air throw and remain under 35dBA, and can handle up to 0.4 in. of external static pressure for ducted installations. www. jaga-canada.com

The AK-RC 251 Optyma control from Danfoss is designed to improve room efficiency and reduce installation time. The electronic controller eliminates the need for mechanical thermostats in cooling applications, along with defrost timers in freezer applications. It can control compressors, solenoids, fans, lights, crankcase heaters and up to two defrosts. www. danfoss.com

The Bitzer Digital Network (BDN) offers cloud-based remote access he Bitzer Digital Network (BDN) offers cloud-based remote access to digital services relating to Bitzer compressors for refrigeration and es relat air conditioning technology, including online monitoring, compressor h operating reports, and troubleshooting.

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The Copeland variable speed reciprocating hermetic compressor from Emerson is designed for commercial refrigeration applications. Compressors are available in 1/8 to 7/8 hp ranges, and feature a brushless permanent magnetic motor to deliver a wide availability of operating ranges for equipment of varying types and sizes, and utilize R-290 refrigerant with a global warming potential (GWP) of 3. www. emerson.com

The single-phase J-IV and J-IVs Airstage VRF heat pump systems from Fujitsu General America are designed for residential and light commercial markets. They serve heating and cooling applications between three- and five-ton capacities, and offer heating capacity to outdoor ambient temperature of -15°F. The J-IVs offers cooling efficiency up to 19.7 SEER, while the J-IV offers up to 19.8 SEER. www. fujitsugeneral.com

Continental Fan’s AFY Yoke-Mount Cooling Fans deliver maximum performance in minimal space. The heavy-duty fans are available in 14- to 42-in. diameters and capacities of up to 34,000 cfm, and feature e an airfoil adjustable pitch h impeller. The AFY is also o available with spark-resistant construction and XP motors. www. continentalfan.com

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