Simultaneous Heating & Cooling

The Air Handling Unit (AHU) preheat coil valve was leaking when signaled closed (0% valve signal), resulting in a preheat discharge temperature that was over 40 degrees warmer than the required temperature. As a result, the cooling coil valve opened simultaneously to maintain the final supply air temperature at its setpoint of 55°F. The simultaneous heating and cooling resulted in excess heating and cooling costs. Continue reading “Simultaneous Heating & Cooling”