Freeze protection activates when the system estimates there is a risk of water freezing in the heat exchanger or the hydraulic circuit.
Potential causes
Low flow, very low water temperature, a stopped circulator pump, or a faulty sensor.
In cooling mode
A very low setpoint or insufficient flow can drop the heat exchanger temperature excessively.
During shutdown
For external piping, protection depends on antifreeze or continuous circulation where specified.
Diagnosis
Actual temperatures, flow, the circulator pump, and sensors should be checked before performing a reset.