Volume 13 Issue 1
July 2015    
ballast - A device required by electric-discharge light sources such as fluorescent or HID lamps to regulate voltage and current supplied to the lamp during start and throughout operation. compatible ballasts - An abbreviated list of common ballasts that will provide the necessary circuitry for a photosensor to operate correctly. Other ballasts may also be compatible; contact the photosensor manufacturer for details. continuous dimming - Control of a light source's intensity to practically any value within a given operating range. capacitor - A device used in electric circuitry to temporarily store electrical charge in the form of an electrostatic field. In lighting, a capacitor is used to smooth out alternating current from the power supply. time delay range - For motion sensors, the range of time that may be set for the interval between the last detected motion and the turning off of the lamps. lamp - A radiant light source. luminaire - A complete lighting unit consisting of a lamp or lamps and the parts designed to distribute the light, to position and protect the lamp(s), and to connect the lamp(s) to the power supply. (Also referred to as fixture.) frequency - The number of cycles completed by a periodic wave in a given unit of time. Frequency is commonly reported in cycles per second, or hertz (Hz). electromagnetic interference (EMI) - The interference of unwanted electromagnetic signals with desirable signals. Electromagnetic interference may be transmitted in two ways: radiated through space or conducted by wiring. The Federal Communications Commission (FCC) sets electromagnetic interference limits on radio frequency (RF) lighting devices in FCC Part 18. electronic ballast - A ballast that uses electronic components instead of a magnetic core and coil to operate fluorescent lamps. Electronic ballasts operate lamps at 20 to 60 kHz, which results in reduced flicker and noise and increased efficacy compared with ballasts that operate lamps at 60 Hz. illuminance - The amount of light (luminous flux) incident on a surface area. Illuminance is measured in footcandles (lumens/square foot) or lux (lumens/square meter). One footcandle equals 10.76 lux, although for convenience 10 lux commonly is used as the equivalent. dimming ballast - A device that provides the ability to adjust light levels by reducing the lamp current. Most dimming ballasts are electronic. power - The power used by a device to produce useful work (also called input power or active power). In lighting, it is the system input power for a lamp and ballast or driver combination. Power is typically reported in the SI units of watts. photosensor - A device used to integrate an electric lighting system with a daylighting system so lights operate only when daylighting is insufficient. lux (lx) - A measure of illuminance in lumens per square meter. One lux equals 0.093 footcandle. nadir - In the lighting discipline, nadir is the angle pointing directly downward from the luminaire, or 0. Nadir is opposite the zenith. driver - For light emitting diodes, a device that regulates the voltage and current powering the source. photovoltaic (PV) - Photovoltaic (PV) cells produce electric current from light energy (photons). PV cells are joined to make PV panels. hysteresis - The dependence of the output of a system not only on its current input, but also on its history of past inputs. The electric light level set by a photosensor with hysteresis, for a certain photocell input signal, depends on whether that photocell signal is increasing or decreasing. Hysteresis provides stable operation in switching photosensors but is undesirable in dimming photosensors.

Are wireless controls economically advantageous?

Manufacturers suggest in marketing materials that one of the primary benefits of wireless lighting controls is reduced installation labor costs due to the avoidance of wiring the sensor to the controller. However, NLPIP found that wireless control equipment is more expensive than equivalent wired equipment from the same brand, as shown in Table 5. Whether or not reduced wiring labor costs outweigh the increased capital costs depends on several factors including:

  • how easily wire can be run through the ceiling and wall
  • the size of the room
  • the acceptability of the surface conduit
  • how familiar the installer is with setting up the wireless control equipment

Because of the uncertainty in the installed cost introduced by these factors, NLPIP recommends obtaining a cost quotation from an electrical contractor to determine if the reduced labor will outweigh the increased capital cost.

Table 5. Online retail prices for retrofit occupancy sensor systems. Occupancy sensor system cost includes one sensor and one controller. Prices are current as of March 2015 and are for a quantity of one for each component purchased separately (i.e. not in a bundle) excluding shipping and tax. Leviton prices are from Gordon Electric Supply at http://www.gordonelectricsupply.com. Lutron prices are from Pro Lighting Group at http://www.prolighting.com. WattStopper prices are from Ready Wholesale Electric Supply at http://www.readywholesaleelectric.com.

Brand Sensor
Motion Sensor System Incremental
Price of Wireless
Compared to Wired
Occupancy System
Model Price per
Price per
$ %
Leviton Wired Sensor OSC04-RIW $76 $111 $89 80%
Controller OSP20-ND0 $35
Wireless Sensor WSC04-IRW $108 $200
Controller WSS10-GUZ $92
Lutron Wired Sensor LOS-CIR-450-WH $80 $110 $59 54%
Controller PP-120H $30
Wireless Sensor LRF2-OCR2B-P-WH $60 $169
Controller RMJ-ECO32-DV-B $109
WattStopper Wired Sensor CI-200-1 $84 $114 $146 128%
Controller BZ-150 $30
Wireless Sensor EOPC-100 $125 $260
Controller EOSW-101 $135

The time needed to pair wireless sensors with controllers should also be included in cost estimates. All of the wireless systems required NLPIP staff to follow detailed written instructions to accomplish this pairing for the first time. The time needed to pair the equipment will typically decrease for subsequent installations as the installer becomes familiar with the procedure. However, NLPIP found that with the Leviton photosensor system, the pairing didn’t occur the first time following the manufacturer’s instructions, and the procedure, consisting of several steps, had to be repeated several times before compatible devices would communicate with each other.


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