While reviewing trend data from an air handling unit, we noticed that the supply air temperature was significantly above the setpoint. Whereas the supply air should have been kept at around 20°C, it got up to 26°C. When we see a problem we often assume that the cause is at the same spot, in this case, we assumed there was something wrong with the air handling unit.

Well, we looked at the cooling coil and the control valve was operating correctly. It was open 100% the whole time the temperature was above the setpoint, which meant the problem was somewhere else. We then followed the source of the energy, which in this case, it was coming in the form of a chilled water loop serving the air handling units. Going upstream, we found our problem; the pumps on the loop were never in operation, meaning the air handling units were not able to cool because no chilled water was being pumped their way.

The lesson learned here for diagnosing HVAC issues is to follow the energy. With access to operational data from the building automation system, we can check in on the various systems and equipment throughout the building and create a virtual pathway of energy. Then when there’s an issue at a particular location, and the cause isn’t at that spot, we know where to go.