I have a 4 ton heat pump unit along with a back-up propane furnace. I have recently had to have the compressor replaced in the outside unit. I have been through 4 or 5 contactors in the past couple of years as well. HVAC technician has previously said that the problem lies with the outdoor thermostat/dual fuel kit mounted inside the heat pump. (It gets too much condensation. I live in southern VA wher it can get pretty humid.) I have replaced the outdoor heat pump t-stat twice and all is well for a while, then it starts to act up again and makes the contactor "chatter" and eventually fail. To try and remedy this, I purchased an indoor programmable t-stat with a wired outdoor sensor. It is dual fuel and 3 heat 2 cool capable.
My question is: After wiring the new t-stat in the same way as the previous one with the addition of the 3 wires for the outdoor sensor, how do I properly disconnect the outdoor heat pump t-stat with the dial on it? I have enabled the outdoor sensor in the menu and believe I have all the settings correct, but the new t-stat is still energizing either the heat pump or furnace, based on outside temperature taken from the old dual fuel kit. If I disconnect the old t-stat in the heat pump it blows the fuse in my furnace. Is there a wire going to the inside t-stat that I no longer need? Do I need to run any additional wires from my furnace to the inside t-stat? I want to be able to control everything from my new t-stat. Everything is working properly right now, but is is basically the same as what I had before, just a new inside thermostat.
Hope all of this makes sense.