In this four-part series, Charles Knuffke, Systems VP & Evangelist, Wattstopper/Legrand, North and Central America and past chair of the Lighting Controls Association provides a crash Lighting Controls 101 class for lighting practitioners. Originally published as the Controls Column in LD+A Magazine in 2023. Reprinted with permission.
This is the third article in a series covering the topic of basics of lighting controls every lighting practitioner should know.
In the previous installments, I covered the different architectures that lighting control systems use and followed up with lighting control outputs and their typical features. Time now to talk about the products that directly influence the operation of a lighting control system: input devices.
A range of devices might be included in a system, but I’d like to focus on the most common ones required in energy codes: switches/dimmers, occupancy sensors, timeclocks, and daylighting controls. In this column, we’ll be talking about the first two; in my last column in this series, we’ll cover the others.
Switches/Dimmers (manual override devices)
These devices may be the most important controls in a space. No matter what the sequence of operation may be, no matter how many layers of control devices control the lighting, an occupant should always have the ability to reduce their light level and be allowed to override the system when needed. If we ignore the desires of the occupant in a space, the result is rarely a positive one.
Common interfaces: Previously, switches and dimmers have directly controlled power to the lights, but modern lighting control systems have turned these into input signaling devices. Switches are usually identified by having one or more buttons that can be used to control loads in the room On/Off or send those loads to a scene where certain loads can each be assigned different levels. Dimmers, on the other hand, often use a rocker or other mechanism—say, a matched pair of buttons to signal “raise” and “lower” for example—allowing the user to increase or decrease the level of one or more lighting switch legs in the space. Networked systems may allow the extension of these features outside the individual room so that a button can control lights throughout the floor, building, or beyond.
Programming: Programming for these devices involves identifying the loads that should be controlled by each switch button or dimmer and what scenario/mode/function/priority (manufacturer terminology varies) you want to take assign to that input.
Another feature, especially useful for dimmers, is the ability to assign fade rates or fade times. For example, the restaurant’s maître d’ may need a button that changes the lighting from an afternoon to evening service using a slow gradual lighting level change; when the cleaners show up at the end of the evening, they want to use another button that drives those same lights to the desired level immediately.
Variation: Not only will the physical format of the switches and dimers differ from manufacturer to manufacturer, but so will their capabilities, the symbols used on the devices (if any), and most importantly, the way the user is expected to interact with the device. Some devices may require a user to press and hold a button, others a quick tap, double tap, or a finger’s slide across the face of the device to access the desired control function.
I learned my lesson early on thanks to a contractor who asked for—demanded, actually—a training session for the end-users at a site. When I offered to bring a copy of the project submittal, I was laughed at and told that for the tenants, the instructions should fit on a 3” x 5” index card. When I showed up with these cards bearing clear instructions on how to use the switches, the tenants in that space were genuinely appreciative. While we in the industry may understand all of a system’s features, don’t expect the users to know unless they are trained.
Occupancy sensors
Occupancy sensors have been available for over 35 years, and while many lighting practitioners have a deep understanding of their application, it is still valuable to cover the basics. These lighting control devices have been proven to offer better returns on investment in certain spaces than others, which is why over time they have been increasingly mandated by energy codes in a growing list of specific applications.
Analog versus digital: Analog occupancy sensors often use a very simple electrical signal to signal occupancy. When used in a networked lighting control system, though, expect that you’ll be required to match sensors with their manufacturer’s lighting control system. This is logical as devices will likely be communicating via the company’s digital protocol.
Detection method: These devices use only a few common technologies to determine the occupancy of a space: passive infrared (PIR), ultrasonic, microwave, and acoustic. When only a single technology is offered in a device, there will be some pros and cons associated with its usage. This is why “dual technology” sensors are quite beneficial. They combine two technologies in a single device to reap the benefits of each technology while minimizing deficiencies of the other, providing a more reliable device.
Settings: A common setting for an occupancy sensor is time delay, or the amount of time a sensor will wait after seeing the last motion before it will send out a signal that the space is unoccupied. Another is sensitivity or gain, which describes the relative level of how the sensor is using that technology versus some maximum level. If you’re using a dual-technology sensor, there may also be options for how its technologies should be used—one, the other, both, or either—before sending out an initial “occupied” command, or to reset its countdown so as not to send out an “unoccupied” command.
Control function: Partial-On sensor operation turn loads On but to a level less than 100 percent. Partial-Off sensor operation instructs loads to not turn completely Off but to some level greater than 0 percent. Vacancy sensor (manual-On) operation provides automatic shutoff but not automatic On. Note that for some lighting control systems, these settings are options found under the load control device, not the occupancy sensor itself. Check to make sure that the manufacturer has taken into account that a manual-On device should still allow a grace period so if it turns lights Off when a person is still in the space, the lights will go back On automatically if it senses motion so that they don’t have to stop what they’re doing and go back to the switch to turn it On.
Application: It is essential to follow a specific manufacturer’s guidelines for the use of their products. Look for the coverage patterns for their sensors, which should be shown on their product cut sheets. Pay attention to any specific warnings such as distance to closest air vent, max mounting, or ceiling height in the space, and dealing with obstructions such as suspended linear luminaires. It is also advisable to check to see if a given product’s coverage pattern is based on NEMA WD-7 testing requirements; this provides assurance that when you compare sensors from two or more manufacturers, the coverage patterns were determined by the same standardized testing.
Moving on
In this Control Column series focused on lighting control basics, we dove into typical input devices and their parameters, starting with switches/dimmers and occupancy sensors. In the last part of this series, I’ll talk about timeclocks and daylighting controls, and provide some concluding thoughts about the evolution of lighting control.
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