having fitted three of these in the last month I have just been back to one of them which has the heater open circuit is there a problem with these or have I just been unlucky.( me thinks that these are not going to be to reliable).
Are you finding the heat pumps sitting in water ? The problem is as much to do with leaks from the tanks as much as the heat pumps themselves on a lot of occasions. The tanks leak water which accumulates under the heat pump which then short out.