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Consider a "Light" Diet

Technology Curbs Energy Cravings

Article written by Jack Carr, P.E., R.S., LEED AP, Criterium Engineers
Published in Condo Media, April 2012

Commercial building owners and condominium boards are looking at the advances in indoor and outdoor light management to learn how it might not only save money but also enhance the environment for their complex. Some of the efficiency improvements have been amazing, but why should we be surprised when much of the lighting technology found in many buildings was around when we last used typewriters?

Bulbs and Fixtures

Most of us are now familiar with the compact fluorescent lamps (CFLs). They are rapidly replacing incandescent bulbs as they use 75% less energy than a standard bulb and last up to 10 times longer.  Replacing a 100-watt standard bulb with a 32-watt CFL can save $30 over the life of the bulb. But what about all of those ceiling mounted standard fluorescent lamps, the most common being the 1.5 inch diameter ‘T12’ lamp. Wise facility managers are converting to new ‘T8’ (1 inch diameter) or ‘T5’ (5/8 inch diameter) lamps to reap the benefits of less energy consumption, higher intensity, and longer life. It should be noted the T5 lamps are not the same length as either the T12 or T8 therefore requiring the entire fixture to be replaced, thus T8 lamps are the more poplar upgrade.

But do not just stop at the new fluorescent lamps. Change the ballasts, too.  The old lamps used ‘magnetic ballasts’. They are apparent when the lamps get old and the lamps fade and flicker. Replacing the old ballast with an ‘electronic ballast’ provides not only flicker-free operation but will save up to 30% less energy. And do not forget the simplest upgrade, clean the fixture’s reflective surfaces to improve optical efficiency or change the lenses or louvers to acrylic diffusers to replace the current polystyrene diffusers that discolor from ultraviolet radiation.

Condos with parking lot pole-mounted fixtures or garage ceiling light fixtures often use High-Intensity Discharge (HID) lamps frequently of the inefficient mercury vapor type.  Like a fluorescent lamp, mercury vapor fixtures require ballasts with harmful substances such as PCBs (Polychlorinated biphenyls).  Other types of old fixtures to consider replacing would be High-Pressure Sodium (HPS) fixtures.   A typical upgrade would be to convert to white light, metal-halide (M-H) fixtures.  If you have standard M-H fixtures you can upgrade to the white-light M-D lamps allowing the retention of the old fixture by installing a pulse-start (PS) system. This will also require the replacement with PS-type ballasts and starters.  

Before we depart from fixture discussions, we should not forget about the exit lights that burn constantly using incandescent bulbs and always seem to burn out compromising the safety and security of the building. The solution is the light –emitting diode (LED) which virtually never burns out. The alternative is the special retro-fit exit lamps that can burn up to 10,000 hours compared to an incandescent exit lamp that will burn only 3,000 hours.

Motion Sensors

Another important lighting energy savings device is the motion sensor. This technology was first developed for security applications but has become widely used for commercial buildings as lighting often can amount to over 40% of the electricity costs. Condos with common lighted areas can also benefit from their use. Motion sensors can replace wall-mounted switches or used in parallel with wall mounted switches to allow an override function.

The most common motion sensors are the Passive Infrared (PIR) Occupancy and the Active Ultrasonic Occupancy sensor. The PIR sensor monitors and detects any significant change in background heat energy in the space. They are calibrated to detect ‘human’ heat on a direct line-of-sight basis to turn on the lights with the presence of an occupant. Conversely, when the heat source is not detected the room’s lights will turn off.

The Active Ultrasonic Occupancy sensor broadcasts a sound throughout the room at a high frequency undetectable by the human ear. These sound waves bounce around the room and around objects in the room. Using the Doppler effect, any movement in the room will be sensed and the fixture is put into the occupied mode and the lights come on. Lack of motion will turn the lights off which can be dangerous in some circumstances so some sensor designs include a dual technology of using both PIR and Active Ultrasonic to provide a safety factor. To extend the energy saving potential further, some sensor models have a daylight override mode that will sense when the room has sufficient light from natural daylight and will turn off the fixtures to avoid wasting unneeded artificial light.

Many sensor devices are not suitable for all applications such as hallways used as a means of egress. There are sensors for this application and your lighting professional can provide guidance. Hopefully with this new light fixture information you can shed some of your energy costs and stay on a conservation diet that will not turn you off.