Luminaire-level lighting controls (LLLC) are a subset of lighting controls in which control functions are integrated into luminaires, allowing individual luminaire control. This approach is highly flexible and responsive, and advanced options additionally offer connectivity to produce data-related benefits. According to a 2020 report by the DesignLights Consortium® (DLC) and Northwest Energy Efficiency Alliance (NEEA), average energy savings can exceed 60% with this approach.
This article defines and describes LLLC technology, system types, advantages and disadvantages, and what’s familiar and distinctive in regards to design and installation.
The LLLC Approach
Definitions for LLLC vary, but the common idea is sensors and control functionality being embedded into luminaires. Today, there is a wide variety of control systems designed around the approach to maximize energy savings while addressing specific user needs.
In the majority of LLLC systems, the three major control elements installed in the luminaire or luminaire retrofit kit are:
Sensors: The sensors may include an occupancy sensor, daylight sensor, or a multipurpose unit combining the two.
Control functionality: This element may be an integral part of the LED driver(s) or a separate device that sends dimming signals to the driver(s).
Wireless or wired connectivity: The luminaires may be wired via low-voltage, low-voltage digital, or power over Ethernet (PoE). Wireless connectivity is achieved via an onboard radio transmitter and receiver connecting the luminaire to an LLLC network using an accepted protocol.
Depending on the system, a fourth element - centralized network hardware and software - may be added as a layer atop the LLLC luminaires. Centralized hardware may include hubs or gateways, which serve as central collection points for managing the flow of data in a network. Data may be stored to a central server or the Cloud for retrieval and analysis.
In January 2021, the NEEA published the 2020 Luminaire Level Lighting Controls Incremental Cost Study. In their report, the NEEA categorized LLLC as Clever, Smart, or Hybrid, producing informal definitions that may be helpful to visualize the offering.
Clever: Clever LLLC systems satisfy basic DLC networked lighting controls requirements for dimming, occupancy sensing, daylight response, and high-end trim.
Smart: Smart LLLC systems build upon Clever capabilities while adding collection and analytic capability for energy and other (e.g., occupancy) data that can be used for Internet of Things (IoT) applications such as space utilization.
Hybrid: Clever-Smart hybrid LLLC systems are Clever systems with energy monitoring capabilities but not advanced data collection.
The foundational LLLC layer places key elements of an autonomous yet groupable control system within each luminaire with a versatile range of inputs and outputs.
Inputs include the occupancy sensor, daylight sensor, manual controls, and any programming. The control functionality decides whether and how to change the lighting based on the commissioning and desired sequence of operations. Depending on the system, outputs may include scheduling, switching, dimming, color tuning, and data.
These combinations of inputs and outputs enact a range of popular control strategies including occupancy/vacancy sensing, daylight harvesting, scheduling, high-end trim (institutional task tuning), manual control/override, color tuning, and more.
With an LLLC-enabled luminaire, we have a single lighting point capable of independently enacting one or more popular control strategies. When networked, the luminaires can participate in multiple, layered strategies that can be modified or custom programmed as needed, using individual luminaires as building blocks. This allows the control solution to be closely adapted to the application so as to maximize energy savings while ensuring occupant satisfaction.
For more advanced systems with centralized connectivity, additional control strategies are available along with useful analytics. This is an area where certain functionalities have become common, while others are still evolving as technology advances.
For example, additional control strategies such as HVAC room temperature, shading, and plug load control can be incorporated. Luminaires can also integrate other sensors, such as air temperature and humidity sensors and low-resolution infrared cameras.
Fine-grained occupancy and other data from highly distributed sensors can be captured for purposes such as space optimization using the manufacturer’s software. Sensor data may also be fed to third-party, and in some cases custom, apps. If paired with Bluetooth or Wi-Fi connections, operators may gain the additional ability to enact asset tracking and contact tracing.
In August 2020, the NEEA published a study seeking to compare one-for-one LLLC retrofits with a comprehensive networked lighting controls (NLC) redesign. This study found that a one-for-one LLLC upgrade produced comparable energy savings and lighting quality as an NLC redesign at a competitive cost in a retrofit in a prototypical open office, an application well suited to LLLC.
In this application, the LLLC options generated 50-74% energy savings for the controls alone (not including the LED upgrade), while the NLC solution demonstrated 67% savings. The highest-performing LLLC had additional features such as scheduling, task tuning, plug load control, and energy monitoring. Meanwhile, the installed cost for the LLLC was roughly one-third to one-half of the NLC redesign option.
Advantages and disadvantages
LLLC offers several advantages as an NLC option. By embedding sensors and control functionality into each luminaire, control is overall highly granular and responsive, which can increase energy savings.
Designer: For the designer, LLLC offers flexibility by reducing the need to predetermine switch leg wiring/zones.
Contractor: For the electrical contractor, it can ensure control compatibility, simplify wiring, and reduce time and risk by eliminating installation of control devices.
Distributor: For the electrical distributor, it offers an energysaving solution that can streamline product schedules for lighting projects.
Owner: The owner gains energy savings, the ability to finetune and reconfigure the system in the future, and potentially advanced functionality/data.
Occupants: Users interact with a lighting system that satisfies energy codes while offering personalization potential.
The primary inhibitors, meanwhile, are the luminaires’ higher base cost, higher complexity of the project, insufficient value or savings for a given project, and uncertain owner interest in advanced functionality. In addition, occupants and designers may have objections to systems that permit every luminaire to operate independently as opposed to in a uniform and coordinated manner.
The advantages often outweigh the disadvantages. Initial costs can be offset through simplified hardware installations and value-added functionality. Additionally, careful system selection can anticipate other concerns and result in a solution that is well-tailored to occupant needs.
The Department of Energy estimated the installed base of networked luminaires will grow from less than 1% currently to about one-third of all lighting in commercial buildings by 2035. Due to its advantages, LLLC is positioned to play a strong role in this growth.
Currently, LLLC is typically installed in office buildings and schools but is also deployed in high-bay, parking garage, gas station, library, and other applications.
Generally, two types of applications are most suitable for LLLC strategies. The first is situations where both luminaire-specific granular control of luminaires and coordinated zonal control is beneficial. Examples include open office coordination of occupancy zones, space requirements, and daylighting zones.
The other is where the use of the granular data from advanced LLLC systems can contribute to space optimization and facilities management. For example, occupancy sensors on every luminaire, combined with detailed building drawings, could be extrapolated into occupant traffic patterns.
Codes and rebates
The 2018 and 2021 versions of the International Energy Conservation Code (IECC) specifically mention LLLC in Section C405.2. This section identifies two paths for compliance with the code’s automatic shutoff, light reduction controls, and daylight response requirements—one based on traditional control devices and the other on LLLC.
In open offices, where IECC requires occupancy sensing with control zoning limited to a maximum of 600 sq.ft., LLLC can simplify installation.
While not mentioning LLLC directly, the upcoming 2022 version of ANSI/ASHRAE/IES 90.1 and the 2022 version of California Title 24, Part 6, effective in 2023, contain similar requirements for limiting the zone size of occupancy sensing in open offices, which provides opportunities for LLLC systems.
Additionally, starting with the 2016 version, the ANSI/ ASHRAE/IES 90.1 energy standard allowed open office lighting to automatically turn on to more than 50% of power as long as the control zone is no larger than 600 sq.ft., which can make LLLC an attractive consideration.
Rebates: A majority of commercial lighting rebate programs incentivize installation of energy-saving lighting controls. Standard rebates incentivize devices such as luminaire-integrated occupancy sensors and daylight dimming systems, for which LLLC systems will often qualify.
In addition, rebate programs that incentivize advanced lighting controls may align with LLLC to allow access to these more comprehensive opportunities. According to the rebate fulfillment firm BriteSwitch, more than one-fourth of rebate programs now separately incentivize installation of NLCs with prescriptive rebates. A majority of these programs qualify products based on listing in the DLC’s NLC Qualified Products List, which in 2022 has been transitioning to the Version 5.0 Technical Requirements. These technical requirements combine required and reported system capabilities, of which LLLC is a reported capability.
Designing with LLLC
As a lighting solution of luminaires, an LLLC system is designed similarly to a standard system. Overall, the lighting must satisfy the owner requirements and the design intent. Attention to detail, however, must be given to aligning task areas and dedicated luminaires.
As a controls solution, an LLLC system can simplify energy code compliance, particularly in complex spaces such as open offices with granular control requirements. If that is the sole goal, a basic (NEEA “Clever”) LLLC system may be appropriate and achieved with relative ease.
With more advanced (NEEA “Smart”) LLLC systems, the control solution may be programmable from a central point, with energy, occupancy, and other data collection. Design flexibility is gained in control zoning. The designer should familiarize themselves with integration and data capabilities for various systems. The designer should also note that the installation of a network may require owner IT buy-in and involvement.
If required by the advanced LLLC system, the designer may need to incorporate the networking hardware (hub, gateway, server) and software into the project deliverables. Some applications can be served by wireless networking, wired networking, or a hybrid wired-wireless solution. The designer must also decide how programming and data will be accessed—web browser, mobile app—and who will be allowed to access it.
Depending on the product capabilities and specific configuration ordered, some LLLC systems can be configured for different control objectives. For example, the designer could zone the direct (task) component of direct/indirect luminaires to be individually controlled but the indirect (ambient) component to be controlled as a group. Or, a row of luminaires might operate independently for occupancy sensing but be assigned to a group for daylight response.
For best results, the designer should produce a clear written controls narrative along with a detailed sequence of operations.
Some LLLC solutions feature all sensors and control functionality pre-installed in the luminaire by a single manufacturer, while others are available as discrete devices that can be added to luminaires in the field.
In particular, when luminaires with pre-installed wireless LLLC are deployed on a project, installation can be greatly simplified. Additionally, sensors, controllers, and drivers are pre-tested as compatible. Depending on the type of LLLC and the needs of the project, there can be fewer requirements to mount discrete sensors (or perhaps no need for discrete sensors), and, for advanced LLLC systems, the amount of supporting hardware is likely reduced. Basic LLLC systems provide further potential benefit during installation because of the lack of supporting hardware, except for switches, in many cases.
If it is a wireless solution, no control wiring is required. This can be particularly advantageous in a lighting upgrade project in an existing building, where utility rebates coincidentally may be available to reduce cost.
Despite potentially simpler installation of an integrated lighting and control system, increased labor should be expected for configuring and commissioning all of the sensors, manual controls, networking/communications between the devices, and additional components such as gateways and central controllers that may be needed depending on the LLLC type and project expectations. Additionally, some coordination with the owner’s IT department may be needed.
Configuration of LLLC systems is often through software accessible via a mobile app (or web browser for centralized systems). For centralized systems, the software is more sophisticated and enables facility operators to organize and program the network and also view the data in a useful presentation format.
Contractors interested in LLLC should familiarize themselves with the technology, particularly the principles of wireless communication, and specific products, which can vary in approach to setup and programming.
LLLC as NLC Option
NLC systems have a well-documented place in buildings as an important tool in addressing the energy efficiency of buildings. LLLC offers an NLC deployment option that places sensors and control functionality within the luminaire, creating a strong value proposition in certain common applications.
For projects with a need to manage overlapping complexity, desire for simplified onsite wiring, or granular access of data as part of a more comprehensive solution, LLLC systems should be considered. ■
Craig DiLouie is education director for the Lighting Controls Association, a council of the National Electrical Manufacturers Association that educates the public about lighting control technology and application (www.LightingControlsAssociation.org).