4  FM quick reads on energy efficiency

1. Energy Savings and Comfort Depend on Sensor Calibration

Today's topic is the importance of keeping sensors calibrated.

We all know the saying, garbage in, garbage out. That phrase applies to the building automation system as much as to any other computer system.

One sure way to reduce the effectiveness of the BAS is to fail to check and calibrate sensors on a regular basis. The BAS uses data from those sensors to control HVAC and other equipment, to issue alarms, and to develop reports. But over time those sensors go out of calibration or stop functioning. The only way to make sure they're delivering accurate data is to put them on a regular maintenance schedule.

Of course, that's easier said than done. Like many preventive maintenance activities, sensor calibration is easy to put off when staff is busy or the budget is tight. But false readings and failed sensors can waste a considerable amount of energy. What's more, they can produce occupant complaints about uncomfortable conditions. If that happens, the facility staff may very well wind up spending time trying to figure out what's wrong and mollifying occupants.

A building automation system is a substantial investment. Keeping sensors calibrated is an important step to getting the value from that investment.

Infrared Cameras Can Help Find Leaks in Ductwork

Today's tip is finding leaks in HVAC ducts.

Leaking ducts can be a pernicious energy waster. They lose heat or cooling &emdash; into the ceiling plenum or other space &emdash; rather than delivering it to occupied areas. What's more, they increase fan energy use because more air has to be moved.

Infrared cameras &emdash; more formally known as thermal imagers &emdash; offer an easy way to find leaks in ducts. The cameras capture an image of heat patterns in objects. An image of a duct would show hot and cold spots, allowing the facility staff to pinpoint leaks in the duct.

Advances in technology have produced cameras that are smaller, offer better resolution, have more features, and cost less than cameras in the past.

Repairing leaks in ducts can produce significant savings. That's because fan energy use is proportional to the cube of the speed of the fan, so they become more efficient at lower speeds. Once duct leaks are repaired, fans will save energy because they are moving less air and moving it more efficiently.

Retrocommissioning Quickly Pays for Itself in Energy Savings

Today's topic is payback for retrocommissioning.

Problems with controls &emdash; HVAC controls in particular &emdash; can waste energy and raise operating costs significantly. The way to find and fix those problems is well-established but too rarely used. Retrocommissioning applies the principles of commissioning to existing buildings rather than to new ones. Studies have shown retrocommissioning to be a cost effective way to improve the performance of controls and to remedy other problems within a building.

Retrocommissioning takes a relatively modest upfront investment. According to a study by Lawrence Berkeley National Laboratory (LBNL), the average cost for retrocommissioning is $.30 per square foot. But the return on that investment comes quickly: The median payback time is a little more than a year. That's not surprising considering that the median energy savings is 16 percent. And those savings last, says LBNL: "Energy savings tend to persist well over at least a 3-to-5 year timeframe." Savings may last longer than that, but the study didn't have data for longer periods.


energy efficiency , comfort , energy management , building automation system , sensors , calibration

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