This indicates that a "Condenser Freeze Condition" has been detected.
A condenser freeze may only occur in heating mode when the water coil is now on the low pressure side of the refrigeration operation.
Safety Notice - This is a high voltage product and contains refrigerant. Only professionals who are qualified to work on such equipment should do so.
For further details on all of the points below, please refer to the product's manual (available for download HERE ).
1. Low (or no) Water Flow Through The Coil
a. Check water valves and pumps for correct operation.
b. Check for blockage in the water coil.
2. Low Water Temperature
a. Check the water temperature, is it below 40º entering?
b. Is the heat pump connected to a closed loop with antifreeze? If so, check that the "FREEZE 1" resistor on the UPM board has been cut to set the unit to antifreeze mode.
3. Low Refrigerant
a. Check refrigerant pressure with your gauge set.
4. Poor Water Heat Exchange
a. Check for scaled water coil.