Adding Value on the Home Front

Nov 1, 2007 12:00 PM, By Carlos Villalobos, Watt Stopper/Legrand

Vacancy and occupancy sensors specifically designed for home applications are now widely available

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.

Most residential sensors are ready to install right out of the box and require only minor setting adjustments.

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.