I have a 2 stage heat pump system. About a month ago the 5 amp fuse for the 24 volt control circuit was shot. I disconnected all the wires at the thermostat, in-door, and out-door units. I check all wires for shorts to each-other and to ground and all was clear. I also ohmed out the coils for the relays. All was clear. I put everything back together and everything worked fine. Yesterday I come home to find the same thing. I checked out all the control wires as I did before and all was clear...again. I put everything back together fired up the system and it ran for about 45 minutes and then cut off. This time the breaker tripped. I reset it and tried it again. The system ran again for about 20 minutes and tripped again. The breaker feels warm to the touch. i tried it again in normal and emergency modes and the breaker tripped all but once when the fuse went. I can leave the breaker on with the thermostat in the off position and it holds.
I am not sure if the issues are related or not. I am wondering if the 24 volt transformer may be on the way out. It is the only component that is on both the high and low voltage sides. Any suggestions.