Geothermal Frozen Water Coil

[mike42]

I have a Climatemaster Tranquility 27, 2 ton, running in open loop. I had some water flow issues that are now resolved, that resulted in low water temp lockouts. The last time, the water coil in the heat pump was frozen and took a while to thaw. The low water temp trip is 30F. Is it normal for the water to freeze in the coil after tripping? Why did it do it only the last time out of 4 similar events? Should I be worried about a bad temp sensor?

[cartercrew]

Is it possible that the temp sensor got moved? I would expect to see a 30* sensor on the leaving water line, but if it was moved to the inlet side, the coil would have to freeze and stop all flow before the sensor responded.

If the sensor is in the correct location, have it tested. Restrict water flow while watching the water temperature to see what temp the switch trips at.

[mike42]

The sensor is original and was never moved, so it should be in the correct position. I guess I should test it. I understand your suggested method for testing it, but is the usual method to remove it and measure the resistance compared to the temperature?