Simple lighting controls are often used in lighting upgrade projects, but rarely are complex additions that affect the building management system (BMS).
So, what are ‘simple lighting controls’?
Simple lighting controls are, typically, occupancy sensors. These are sensors that, when triggered, will turn lights ‘ON’ automatically and turn lights ‘OFF’ after a pre-determined amount of time passes.
Industry standards adds an automatic occupancy sensor (often referred to as ‘motion sensor’) in commercial buildings, small single-person offices. This can yield between a 20-25% energy savings by removing their traditional ON/OFF toggle switch and adding these types of sensors.
Here are few important points to keep in mind when installing sensors:
- Type of sensors
- Lighting design layout
- Installation height matters
- Understand what assumptions are being made about the sensors
Let us decode that for you.
Sensor type 1: Passive Infrared (PIR) detects the difference in long-range radiation between objects and their background. If no motion is sensed over a pre-determined period of time (perhaps 60 seconds to 60 minutes) the lights are turned “OFF”. It is important to note PIR requires a direct line of sight, so furniture and obstructions can easily block proper operation.
Sensor type 2: Ultrasonic Sensor (US) emits low intensity, high frequency inaudible sound waves to detect motion from the changing return echo patterns. If no motion is detected over a pre-determined period of time, the lights automatically switch to “OFF”. This technology can cover large enclosed spaces, even with partitions. However, they are very sensitive to ‘false’ triggers such as air motion from the HVAC system, ceiling fans, etc.
Having a lighting layout including occupancy sensors completed is never a bad idea.
Providing a layout of the existing building, with room dimensions, will allow for this to be accomplished. And, just like anything, there are well-vetted products in the industry and those known to not perform well. Using a trusted advisor or doing your homework is very important, even with a wall mounted occupancy sensor.
It is important to make sure you use sensors that are meant for the height they are mounted. That is, if the fixture-mounted sensor is 40’ above the ground, the sensor must be capable of that range. Standard ranges are either 25’ (or less) or 40’ (or less).
Understand what assumptions are being made about the sensors.
Lastly, it is important that the facility owner, operator or manager, understands what assumptions are being made with the sensors. About three years ago, we were in a very competitive bid situation for a project for multiple industrial facilities, spanning multiple states. It was brought to our attention during the bidding process that our energy savings was not as much as our competitor. When a deep dive was done, it was uncovered the competitor was assuming occupancy sensors would have lights turned “OFF” 80% of the time, throughout the entire plant floor. Obviously unrealistic, but buried in their bid, where it was not obvious.
Once this was uncovered, it was easy to award us the project, especially since it was also uncovered the unscrupulous bidder was using more annual burn hours (over 9,000) than actually exist in a year (8,760). For retrofit, where simple payback is usually the determining factor for a project, make sure the assumptions for burn hours AND even for occupancy sensors are in line with reality.
For industrial applications, adding occupancy sensors are a little different, but the concept is the same. I recall a steel plant we retrofitted about 5 years ago, with 24/7 production in 2/3 of the space and storage in the rest. Our audit uncovered the 200,000 square foot facility would benefit having sensors added to the storage space, mainly because second and third shifts rarely had people in that part of the building. We audited the space by using data loggers, these loggers track motion in a space and record it as data. After two weeks of data logging, we concluded the storage space would save about 65% during 2nd shift operations and north of 80% during 3rd shift.