Making sense of sensors

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Ari Hoffman
Energy and Sustainability Services

The simplest and most effective energy reduction measures can come from tenant education and lighting management.

There are many effective retrofit strategies that can be undertaken at a facility. Click here for an example. The simplest of all is not to turn on the lights to begin with, or turn them off when they are not needed.  However, in many buildings the lighting systems are not on a timer system, or the lighting schedule has not been evaluated against tenant work schedules.  In existing buildings, installation of a lighting control panel or re-evaluation of an existing schedule should be the first step towards reducing the lighting load. 

Lighting controls are becoming almost standard items for building out office space, and the range of options in sensors is increasing as well. Basic occupancy sensors use sound or motion reduce or turn off lights when no occupants are present, while dual-technology sensors require both sound and motion to turn lights on and either sound or motion to stay on, in order to minimize accidental triggering. If you’ve ever been In a meeting when the lights went out simply because you failed to wave your arms sufficiently, you can appreciate the value of dual-technology sensors

Then there are daylight sensors, which use photocells to measure natural light levels and sets artificial light levels accordingly. Photocells are an increasingly popular option on occupancy and dual-technology sensors to optimize light levels whether someone is present or not.

In transitional spaces such as bathrooms, copy/mail rooms and stairwells it may make sense to remove traditional on/off switches and install wireless sensors, which are preferred over traditional sensors when running wire behind existing finishes would be cost-prohibitive. Pricing for wireless hardware is higher than traditional devices but the cost is starting to come down.

Occasionally sensors need to be adjusted, either because they were not installed in the right place to begin with, or because furniture layouts have been reconfigured in ways that affect their operation. If a sensor in a perimeter office turns on whenever someone walks by the office, it should be recalibrated to narrow the zone or reduce its sensitivity. Time delays can also be adjusted. 

On a LEED for Commercial Interiors project, up to four points can be earned for sensors pending on the extent of their use.  Building codes such as California’s Title 24 code also mandate the use of sensors during new buildouts, using a lights-off requirement as part of an overall strategy of energy usage reduction.  For the future, automated “load shedding” will become more of a factor in building codes, requiring IP addressed “smart” ballasts and control panels to further reduce lighting power usage.

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