Introduction to Luminaire-Level Lighting Controls

Luminaire-level lighting controls (LLLC), also called embedded controls, are lighting control systems in which sensors and controllers are installed within luminaires to enable autonomous, individual luminaire control. By making each luminaire a control point, control is highly flexible, responsive, and therefore generally more energy-saving. Additionally, significantly detailed space use data can be generated as a potential feature. According to a 2020 report by the DesignLights Consortium (DLC) and Northwest Energy Efficiency Alliance, average energy savings exceed 60%.

Serving as a preview for an upcoming Education Express course, this article published by the Lighting Controls Association describes LLLC technology, system types, advantages and disadvantages, studies characterizing energy savings and cost, and what’s familiar and distinctive in regards to design and installation.

Image courtesy of Lutron Electronics

Defining LLLC

The DLC defines LLLC as:

The capability to have a networked occupancy sensor and ambient light sensor installed for each luminaire or kit, and directly integrated or embedded into the form factor during the luminaire or kit manufacturing process.

The International Energy Conservation Code (2018, 2021) defines LLLC as:

A lighting system consisting of one or more luminaires with embedded lighting control logic, occupancy and ambient light sensors, wireless networking capabilities, and local override switching capability where required.

?The Northwest Energy Efficiency Alliance (NEEA) defines it similarly as:

A type of networked lighting control (NLC) system with integrated sensors and controls in each luminaire that are wirelessly networked, enabling the luminaires within the system to communicate with each other and transmit data.

The controls package may be delivered via an LED luminaire or luminaire retrofit kit. Note that while this article follows these essentially similar definitions, manufacturers offer a variety of approaches to the basic concept. For example, the lighting controller (intelligence) may reside external to the luminaire, or the luminaires may be wired via low-voltage, low-voltage digital, or power over Ethernet (PoE).

The LLLC system

As indicated by the definitions, the three major control elements pre-installed in the luminaire or luminaire retrofit kit are 1) sensors, 2) controller, and 3) wireless or wired connectivity.

Image courtesy of Acuity Brands

The sensors may include an occupancy sensor, light sensor, or a multipurpose unit combining the two. The controller, which contains a programmable microprocessor, may be an integral part of the LED driver(s) or a separate device that sends dimming signals to the driver(s). Wireless connectivity is achieved via an onboard radio transmitter and receiver connecting the luminaire to an LLLC network.

Because these elements are installed in the luminaire at the factory, compatibility is assured, controls installation is simplified, and the luminaire arrives programmable or with a preprogrammed sequence of operation.

Depending on the system, a fourth important element may be added as a layer atop the LLLC luminaires, which is the network hardware and software.

Hardware may include hubs or gateways and a central server. Hubs and gateways serve as central collection points for managing the flow of data in a network. The central server stores the data. The software, accessible via a web browser or mobile app, enables facility operators to organize and program the network and also view the data in a useful presentation format.

LLLC as a platform

The basic LLLC layer places an autonomous yet groupable control system within each luminaire with a versatile range of inputs and outputs.

Inputs include the occupancy sensor, light sensor, manual controls, and any programming in the controller such as schedules. The algorithm residing in the controller receives these control signals and decides whether and how to change the lighting, based on the desired sequence of operation.

System outputs include switching, dimming, color tuning, and data.

These combinations of inputs and outputs enact a range of control strategies including occupancy/vacancy sensing, daylight response, scheduling, high-end trim (institutional task tuning), manual control/override, circadian-supportive strategies, and more.

Connectivity

With an LLLC-enabled luminaire, we have a single lighting point capable of independently enacting a range of control strategies. With wireless connectivity, these luminaires can be joined in a network without the need of data cabling. The same functionality can be achieved with wired LLLC with the use of data cabling between the luminaires. (This article focuses on wireless communication.) The network allows a number of capabilities expressed in varying degrees in products.

First, the system becomes programmable at the installation. While the system may be preprogrammed at the factory for energy code compliance, wireless connectivity enables custom programming and creation of sophisticated solutions using individual luminaires as building blocks. Luminaires can be grouped, assigned to one or more control zones and strategies, and given a sequence of operation, any of which can be changed at any time. Because the network is wireless, this can be implemented independent of both control wiring and lighting circuiting.

Image courtesy of Cooper Lighting Solutions

Integration

As second capability of LLLC produced by connectivity is serving as a platform for integration to enact additional control strategies and generate useful analytics. This is an area where certain functionalities are commonplace, while others are still evolving as software technology advances.

Image courtesy of BetterBricks

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.

If the network links to a central server, 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 can also be fed to third-party, in some cases custom apps. Paired with Bluetooth or Wi-Fi connections, operators gain the additional ability to enact asset tracking and contact tracing.

System types

In a 2021 study, the NEEA informally classified LLLC systems as belonging to one of three types. Each delivers a distinct set of capabilities and cost.

Clever LLLC systems satisfy basic DesignLights Consortium (DLC) Networked Lighting Controls (NLC) Qualified Products List (QPL) requirements for dimming, occupancy sensing, daylight response, and high-end trim. Luminaires may be designed for a plug-and-play installation that require little or no additional programming during the install.

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.

Clever-Smart hybrid LLLC systems are Clever systems with energy monitoring capabilities but not advanced data collection.

Advantages and disadvantages

With such robust capabilities, LLLC offers significant advantages.

Overall, by making each luminaire a control point, control is highly flexible, responsive, and therefore typically more energy-saving, while potentially yielding highly detailed space usage data. According to the NEEA, average energy savings exceed 60%.

For the electrical contractor, LLLC can ensure control compatibility, simplify wiring, and reduce time and risk by eliminating installation of control devices. For the electrical distributor, it offers an energy-saving, value-added solution that can streamline product schedules for lighting projects.

The designer gains flexibility by eliminating the need to predetermine switchleg wiring/zones. The owner gains high energy savings, potentially data, and the ability to fine-tune and reconfigure the system with relative ease in the future. And users interact with a lighting system that respects comfort while offering personalization potential.

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The primary inhibitors are the luminaire’s higher base cost (which may be offset to an extent by reduced installation labor cost), potential higher complexity of the project if a Smart system is deployed, insufficient value or savings for a given project, and uncertain owner interest in non-energy benefits generated by collecting data.

As with any lighting or control solution, the approach must be appropriate for the given application. For example, luminaires in a hospital MRI room, where wireless communication may produce interference with specialized equipment, may not be an appropriate match for LLLC.

LLLC and energy codes

The simplicity and strong energy savings available from LLLC is reflected in the 2018 and 2021 versions of the International Energy Conservation Code (IECC), a popular model commercial building energy code. Section C405.2 identifies two paths for compliance with the code’s mandatory lighting control requirements, one based on remote 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. The 2022 version of California Title 24, Part 6, effective in 2023, contains a similar requirement for occupancy sensing in open offices.

Starting with the 2016 version, the ANSI/ASHRAE/IES 90.1 energy standard allows 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., removing an impediment to LLLC.

LLLC and 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, which can fall under the category of LLLC.

According to rebate fulfillment firm BriteSwitch, more than one-fourth of rebate programs now separately incentivize installation of networked lighting controls, including LLLC-based systems. A majority of these programs qualify products based on listing in the DLC’s NLC Qualified Products List, which in 2022 was transitioning to Version 5.0 Technical Requirements. These technical requirements combine required and reported system capabilities, of which LLLC is a reported capability.

Applications

The Department of Energy estimated the installed base of networked luminaires will grow from less than 1% currently to nearly a third of all lighting in commercial buildings by 2035. 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 general luminaires are highly suitable for LLLC. The first is luminaires with high wattage and long operating hours, which would benefit most from enhanced energy savings. The other is any luminaire where lighting control is appropriate and where occupancy or other data for the space is beneficial to collect.

LLLC energy savings study

In August 2020, the Northwest Energy Efficiency Alliance (NEEA) published a study seeking to compare one-for-one LLLC retrofits with a comprehensive networked lighting controls 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.

The researchers set up four workstations at the center of an 891-sq.ft. space that was 33 ft. wide east-west and 27 ft. deep north-south, with perimeter glazing along the northern face, as shown in the below plan. The baseline lighting system consisted of nine 4-ft. indirect/direct 32W T8 pendant luminaires laid out on a 3×3 grid and controlled by a wall switch.

Image courtesy of Northwest Energy Efficiency Alliance

Five systems were installed, which included four LLLC options of increasing features (most of them qualifying them as NLC systems themselves) along with a more comprehensive NLC system. The NLC redesign system featured remote ceiling-mounted sensors (four occupancy, two daylight, configured in the graphic) and software-based control zoning of luminaires as well as data output for space utilization and asset tracking. All options involved a one-for-one replacement of the fluorescent luminaires with LED luminaires tuned to produce around 30 footcandles.

Image courtesy of Northwest Energy Efficiency Alliance

Based on the monitoring, 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. The researchers acknowledged the space was particularly well suited to LLLC as opposed to a more comprehensive solution.

In this space, the installed cost for the LLLC was roughly one-third to one-half of the NLC redesign option.

The NLC performed best for savings due to high-end trim but lowest for occupancy and daylight sensing, which is due to fewer sensors and less granularity in the control response. And of course the NLC provided a significant non-energy benefit related to occupancy tracking.

All of the systems installed generally smoothly and without delays, though there were some challenges in equipment acquisition. The time and complexity involved in programming and commissioning varied across the systems.

Participants regarded the indirect/direct lighting favorably but without any clear preference across the control systems.

LLLC cost study

In January 2021, the NEEA published the 2020 Luminaire Level Lighting Controls Incremental Cost Study. The study was designed to estimate the average incremental installed cost (product plus labor) of LLLC to the end-user compared to LED luminaires with no controls. As a secondary goal, NEEA also compared the incremental cost of LLLC to luminaires plus controls installed to achieve minimum energy code compliance.

The NEEA’s research included interviews of 16 manufacturers and manufacturer representatives and involved collection of 19 project cost estimates based on prototypical office buildings. Cost estimates were itemized for detailed analysis. The result was an estimated average cost per luminaire and square foot for Clever, Smart, and Clever-Smart systems.

NEEA estimated a total average incremental cost for LLLC:

• $49 per luminaire for Clever systems
• $90 per luminaire for Smart systems
• $63 per luminaire for Clever-Smart hybrid systems

This is compared to the average installed cost of LED luminaires without any controls, which served as the main comparison baseline.

Based on a 40,000-sq.ft. prototypical office building, the average incremental cost breaks down to:

• $0.58/sq.ft. for Clever systems
• $1.16/sq.ft. for Smart systems
• $0.78/sq.ft. for Clever-Smart hybrid systems

Between 2019 and 2020, NEEA’s analysis revealed:

• 17% decrease in average incremental cost for Clever systems
• 20% decrease in average incremental cost for Smart systems
• No change in average incremental cost for Clever-Smart systems

Between 2017 and 2020, NEEA’s analysis revealed:

• 28% decrease in average incremental cost for Clever systems
• 16% decrease in average incremental cost for Smart systems
• 21% decrease in average incremental cost for Clever-Smart systems

The NEEA study demonstrates that average LLLC cost is declining over time, making this option more attractive for lighting upgrades and new construction.

For Clever systems, the primary value proposition is installation simplicity, application flexibility, and maximum energy cost savings.

For Smart systems, the primary value proposition goes beyond that of Clever systems by achieving non-energy benefits through data collection and analysis.

In new construction, the incremental cost of making the lighting system “Internet of Things ready” with LLLC for a prototypical office building is an average 15% higher than a lighting system that satisfies code minimums and 7% higher than a basic LLLC system that maximizes energy savings.

Image courtesy of the Northwest Energy Efficiency Alliance

Designing with LLLC

On the lighting side, an LLLC system is designed similarly to a standard system. Overall, the lighting must satisfy the owner requirements and basis of design. Attention to detail, however, must be given to aligning task areas and dedicated luminaires. In an open office, for example, a typical luminaire serves 80-120 sq.ft., while the control zone for an onboard occupancy sensor can be limited to a roughly 8×8 area, suitable for 10×10 workstations.

Image courtesy of the Integrated Design Lab

On the controls side, an LLLC system can simplify energy code compliance, particularly in complex spaces such as open offices. If that is the sole goal, a Clever LLLC system may be appropriate and achieved with relative ease.

With Smart systems, the LLLC is programmable from a central point, with energy and possibly occupancy and other data collection. Design flexibility is gained in current and future control zoning, and the designer can spend their time on optimizing energy savings, performance, and resulting design value rather than checking boxes for code compliance. The designer should familiarize themselves with integration and data capabilities for various systems (such as the occupancy “heat” map example shown below) and communicate this value to the owner. The designer should also note the installation of a network may require owner IT buy-in and involvement.

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Using LLLC luminaires as design building blocks, 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.

The designer should be sure to produce a clear written controls narrative (sequence of operations, or SOO) for the control system, which describes what each control point does in response to what inputs. A simple example is shown below for an open office LLLC installation.

Image courtesy of BetterBricks

?The designer will need to provision the networking hardware (hub, gateway, server) and software. Some applications can be served by wireless networking, others by 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.

Wall stations

?Ideally, automatic control effects implemented by LLLC luminaires should be transparent to any users in the area, necessitating attention to continuous dimming and fade rate. The most tangible interaction with the control system occurs at the manual control interface: the wall station, which may be wired or wireless (powered by a battery). The wall station provides users the ability to override the system, choose light level, and potentially select preset lighting scenes.

The designer should put themselves in the user’s shoes and provide the right interface—intuitive and simple to operate, with consistent, easily understandable labeling.

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Installing LLLC

Assuming the solution is properly designed and a good fit for the application, installation is theoretically simplified. Sensors, controllers, and drivers are pre-tested as compatible and pre-installed in the luminaire. One therefore does not need to mount discrete sensors in the ceiling or install either control panels in the electrical room or distributed controllers in the ceiling plenum, at least for the spaces where LLLC is installed. 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.

Image courtesy of BetterBricks

Despite potentially simpler installation of an integrated lighting and control system, labor may be required for setting up the network, and additional components such as gateways may need to be installed. Luminaires must be discovered on the network and may require being assigned to groups and programming via software. Some coordination with the owner’s IT department may be needed.

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.