I am getting ready to take a look at a duel fuel system, first time to do so. I have not ever had the experience to work on one before. It is heat pump/ gas furnace system. It belongs to a friend of mines neighbor. I know from conversations that his fuel bill has really gone up since he or someone has installed a new T-stat. I would appreciate very much if anyone could enlighten me in the correct wiring procedure. I haven't called on the home yet and taken a look, don't know as if it is a digital or conventioal T-stat. First system I have heard of here, in Texas.