The graph demonstrates the results of retro-commissioning for one rooftop unit. The retro-commissioning authority found improper damper operation in economizer mode. Instead of fully opening the outdoor air damper to provide free cooling, the actuator fully closed the outdoor air damper and provided 100% return air to the space. Mechanical cooling was required at an increased demand of 30 kilowatts. The damper operation was immediately corrected simply by reversing the actuator operation from clockwise to counter-clockwise. This identical error also forced morning warm-up to occur with 100% outside air. Imagine trying to heat your building when you are blowing in 10,000 cubic feet per minute of air at 15 degrees. This is equivalent to a one bedroom studio apartment, every minute. Based on operator feedback and maintenance records, this unit did not operate properly from the date of original installation – ten years ago.
The problem outlined above is one of a number of common items found in retro-commissioning projects. Any of the following problems can reduce occupant comfort and increase your operating costs:
- Manufacturer’s initial quality
- Installing contractor’s errors
- Control programmer’s misunderstandings,
- Equipment degradation due to normal wear
- Improper operation by building operating staff.