Defrost operation applies only to air source VRF outdoor units in heating mode operation. The strategy may be either Reverse-cycle or Resistive. The ‘Reverse-cycle’ option will temporarily run the outdoor unit heat pump in cooling mode, rejecting heat via the condenser coils to remove any ice/frost build-up. The ‘Resistive’ option will simply operate an electric resistance heating coil to melt the ice/frost build-up
Select the meter for reporting the defrost energy.
When a resistive defrost strategy is selected, the resistive defrost heater capacity must be specified.
Defrost control may be either Timed or On-demand. When timed, specify the defrost time fraction. This is the fraction of the total time below the specified Max outdoor temp. for defrost operation that will be dedicated to running the defrost cycle. When on-demand, the defrost time fraction is calculated based on outdoor weather (humidity ratio) conditions.
Defrost does not occur when outdoor temperature is above the specified Max outdoor temp. for defrost operation.
