Make sure the control is in occupied mode and not in morning warm-up mode. Enable the VAV occupied heating feature. If the return air temperature drops below the VAV occupied heating setpoint, all cooling stages de-energize after all compressor minimum runtimes have expired. If the system controls a cooling valve instead of cooling stages, the valve closes down to 0%.
After the two minute cool to heat changeover delay has expired, all heat stages energize with approximately 30 seconds of delay between stages. If the system controls a heating valve instead of heating stages, the valve opens to 100%. Heat remains energized until the return air temperature exceeds the VAV occupied heating setpoint.