The morning warm-up feature runs during the first hour of occupied operation. The system enters cooling mode at the end of the hour and the SAT adjusts to meet the SAT setpoint. Morning warm-up functionality is available on RTUs with SMART Equipment controllers.
RTU
Enable the morning warm-up feature so that the RTU can use the morning warm-up strategy. Before energizing heat for morning warm-up, the system runs the fan for five minutes, then determines if morning warm-up is needed based on the Return Air Temperature (RAT).
If the RAT indicates that morning warm-up is required for the zone, the system operates all stages of heating simultaneously at the RTU. If the system controls a heating valve instead of heating stages, the heating valve opens to 100%. If the morning warm-up RAT setpoint is met before the one-hour morning warm-up period ends, the system waits until the one-hour time period expires before entering the occupied cooling mode. The system continues to operate the fan and monitor the RAT until the scheduled occupied period begins. The system may re-enter the heating mode if the RAT drops two degrees below the morning warm-up RAT setpoint. If the scheduled occupied period does not meet the morning warm-up RAT setpoint, the system enters occupied cooling mode. The economizer remains closed until the occupied period begins.
During the morning warm-up operation, the supply fan adjusts the duct static pressure to meet the current setpoint of the duct static pressure.
VAV box
During morning warm-up or VAV occupied heating, the VZC passes the SAT value from the RTU controller to the zone damper controller. The zone controller compares the SAT to the zone temperature and automatically determines when the system is in morning warm-up or VAV occupied heating based on the difference. In morning warm-up mode, the zone controller adjusts the zone temperature to meet the occupied heating setpoint.To adjust the zone temperature, configure the damper to deliver the maximum primary heating, such as control damper to cooling maximum flow, and stage the optional box or supplemental heating as needed. Supplemental heat is used before box heat if both heating strategies are present. In the zones that do not require heating control the supply flow to the warm-up minimum flow. For example, if the zone temperature is higher than the occupied heating setpoint.