In the illustrated terminal reheat multiple zone system, what statement represents the functioning of the supply air duct thermostats controlling the preheater steam flow and the cooling coil chilled water flow? GS-RA-42 Illustration GS-RA-42: the U.S. Coast Guard has not released this illustration.

Correct Answer: Option A — The thermostat controlling the preheater steam flow is set several degrees lower than the design cooling coil off-coil temperature to prevent simultaneous flows.

To prevent simultaneous heating and cooling, which wastes energy, the preheater thermostat is set lower than the cooling coil's off-coil temperature. This deadband ensures the preheater only activates when the air temperature falls below the cooling threshold, preventing the system from fighting itself and maintaining optimal thermal efficiency.