Many of today's homeowners are enthusiastic about energy-saving products, especially those that boast a quick payback. Vacancy and occupancy sensors are not only meeting this efficiency need, but also helping reach the latest energy code requirements, such as California's Title 24. Electrical contractors who select and install residential occupancy-based controls can add value to their projects and differentiate their services by offering customers a “green” solution.
The variety of controls developed specifically for residential applications has increased dramatically in response to this growing demand. And consumers are enthusiastically accepting these products, as evidenced by the Home Lighting Control Alliance, a Warrenton, Va.- based self-funded, member-driven consortium of lighting control manufacturers, systems integrators, and industry support organizations, which reported that the adoption rate for lighting control in new, single-family homes had tripled in a single year.
Once contractors understand the expanded range of available control strategies and options, they can confidently install and set up occupancy-based controls throughout a home.
Passive infrared sensors
Residential occupancy-based controls are typically passive infrared (PIR) devices that fit into a single-gang box and simply replace a traditional wall switch. Sensors include the basic toggle function, but also add automated control features based on occupancy. They work by sensing body heat — contrasted against the cooler surroundings. Each sensor includes a lens that is used to determine the coverage area and sensitivity for that particular device. A good-quality sensor can see a full 180° and sense a space of 600 to 900 square feet. However, care must be taken to locate a sensor within direct line of sight of the area it's intended to monitor.
Sensors save energy by turning lights off when no movement (occupancy) has been detected for a specific period of time, which is known as the time delay. Different length delays are appropriate for different applications. The goal in selecting a time delay is to maximize energy savings without compromising user safety or comfort. A long time delay, such as 30 minutes, works well in a bathroom where an occupant might take an extended bath or shower out of view of the sensor. A laundry room or hallway could use an even shorter delay. The key is to avoid false offs in spaces where there might be minimal movement when the area is occupied.
Wiring wall switch sensors is straightforward because they are self-contained devices. Most residential sensors require a neutral connection, which is an important safety feature, as it prevents the device from leaking current to ground. For retrofit applications without neutrals, safe 2-wire devices are available but will be limited to controlling incandescent loads. All controls should be properly grounded, and specific load requirements should be confirmed before installation. Residential wall switch sensors are available to control small motor loads as well as lighting loads, including incandescent, low voltage with magnetic or electronic transformers, and linear or compact fluorescents.
Occupancy sensors vs. vacancy sensors
The first step in choosing the best product for a particular application is determining the control strategy appropriate to the space in which it will be used. Residential occupancy-based controls are named based on their mode of operation, falling into one of two categories: occupancy sensors or vacancy sensors.
Occupancy sensors automatically turn the lights on as soon as they detect occupancy. When a time delay has been reached without further occupancy being detected, they turn the lights off. If desired, occupancy sensors may be manually overridden to keep lighting off as needed.
Vacancy sensors detect when a space is vacant and turn the lights off following a time delay. They feature manual-on operation, which has several benefits. Because they don't automatically turn lights on when motion is detected they are ideal for the many applications that don't routinely require lights to be on when the space is occupied. Vacancy sensors can maximize energy savings for many residential applications by ensuring the lights are not turned on unless they are needed. Households with pets are good candidates for vacancy control as there is no possibility of a false on.
The California Energy Commission understands the energy-saving potential of manual-on sensors. Title 24 dictates this control option for residential projects if builders are using controls in lieu of high-efficacy light sources in certain applications. Contractors should note that some sensors can operate either as occupancy or vacancy sensors based on a configuration option.
Special switching options
Once the sensor type has been selected, you can consider whether the application involves any special switching requirements. An area with multiple entrances, such as a Jack-and-Jill bathroom, a hallway, or a staircase might not be suited to switching from a single location, but instead require 3- or 4-way control. Alternately, the homeowner might wish to switch two loads separately from a single location, such as a bathroom fan and light.
Multi-way sensors are available for applications requiring several switching locations. By installing sensors in two or three locations, coverage is extended to include areas within the line of sight of any of the connected sensors. Lighting is held on for the time delay period after the last sensor in the group ceases to detect motion. When choosing multi-way sensors, be certain that the model selected offers full multi-way control.
Dual relay sensors offer a perfect solution for switching separate loads from one location and can be especially useful for retrofits. Housed in a single-gang device, dual relay sensors give contractors the option of splitting control of two loads or adding a load without having to install a larger box.
In addition to PIR circuitry, some sensors also contain photocells that measure the amount of ambient light. With this added input, automatic-on occupancy sensors in areas with windows or skylights can be set up to turn lights on only if light levels are low when occupancy is detected, saving more energy than standard occupancy sensors. A light level sensor could be just the right choice for a daylit laundry room, a space people tend to enter or exit with their hands full, making a manual-on switch an awkward choice. The light level sensor would keep lights off when the space was bright, but turn them on automatically when the space was dark and someone entered. Of course, such sensors can be turned on manually.
Setup and maintenance
For the most part, sensor set up involves a couple of quick one-time adjustments. If the device has the option of automatic- or manual-on, this parameter may need to be configured from one option to the other. In most cases, the only other adjustment needed is to set the time delay. This is generally done with a screwdriver-adjustable trim pot. As noted earlier, set long time delays for areas that experience extended periods of occupancy and/or where occupants may move only minimally. Set shorter time delays for areas that will experience short durations of stay.
When a sensor includes a built-in light level sensor, it should be factory set to the maximum light level. This ensures that the daylighting option does not come into play unless it is specifically required. When using the option, gradually decrease the light level adjustment until lighting comes on at the desirable threshold.
The contractor should test the sensors as the final step of the installation process. Place each device in test mode, which temporarily shortens the time delay, and check to ensure that the sensor does indeed turn the lights on (if applicable) and off — and that it properly senses movement within its line of sight. Once the sensor is set up, you can confidently walk away, knowing it will operate consistently over time with no maintenance.
Staying on top
According to the “Builder Technology Market Survey,” conducted by the Consumer Electronics Association (CEA) in conjunction with the National Association of Home Builders (NAHB), lighting controls represented the second biggest increase of any home technology — over home theater, multi-room audio, and structured wiring.
As with so many things in life, the array of choices on the market can sometimes be more of a curse than a blessing. How can a busy contractor best keep track of so many options and offer customers features tailored for each application without spending an inordinate amount of time setting up and adjusting sensors? By familiarizing yourself with the benefits of the latest generation of residential control products, you will be in the best position to take advantage of your clients' growing interest in controls.
Villalobos is senior product development manager with the Watt Stopper/Legrand, Santa Clara, Calif.