A18.104.22.168 Controls for Heat Pumps With Supplementary Electric Resistance Heaters
In which the cut-on temperature for compression heating is higher than the cut-on temperature for supplementary heating and the cut-off temperature for compression heating is higher than the cut-off temperature for supplementary heating.
Exceptions: The controls may allow supplementary heater operation during:
- Defrost; and
- Transient periods such as start-ups and following room thermostat setpoint advance, if the controls provide preferential rate control, intelligent recovery, staging, ramping or another control mechanism designed to preclude the unnecessary operation of supplementary heating.