Incomplete testing and lack of design review
This police headquarters required an overhaul of its air handlers, building automation system, and lighting system.
Due to the high energy use at this all-electric police building, exp U.S. Services was brought in to perform retro-commissioning and assess the problems and potential for energy savings. This large, 12-year-old, 5-story building houses the administrative offices for the police department, which was supposedly occupied 24/7. In reality, only a small portion of the building is occupied continuously. Two large air handling units (AHUs) serve the entire building through variable air volume (VAV) and fan-powered boxes (FPBs).
During the inspection, 20 of the 100 perimeter FPBs were found inoperative. These boxes are the only source of heat, and tenant comfort issues were common. Further investigation revealed some incorrect coding in the building automation system (BAS) programming was permanently holding these boxes in “unoccupied” mode. This error was corrected quickly, and all boxes began functioning properly. Although this was not directly an energy conservation item, it allowed the building operators to shut off the AHUs during winter nights because the FPBs would operate independently, and provide heat as needed. It appears that the BAS programming for these particular boxes was overlooked during the initial start-up of the HVAC systems.
The lighting in the building is adequate, and reasonably efficient fixtures were used, but at some point during design, the wall-mounted light switches were “value-engineered” out of the building. The theory was because the building would be occupied 24/7, the lights would never be off, and the switches were superfluous. In reality, only a small portion of the building is occupied continuously and the lights are left on 24/7, wasting large amounts of energy. Area-wide lighting controllers were installed, but subsequently taken out of service due to complaints of lights going off at the wrong times or other problems.
It seems that the proper design review by the CxA would have addressed this issue, and perhaps suggested an alternative design, such as occupancy sensor light switches that would control the local lighting and avoid the current energy waste. exp’s recommendation was to install an occupancy-sensing switch for each lighting circuit in the building. Although a costly option, the annual savings are 1,440,000 kWh and $102,000 for a payback of less than 1 year.
Terrence Malloy is project manager for the energy solutions group at exp US Services Inc. He focuses on energy conservation, retro-commissioning, and renewable energy systems.