I found out the hard that that is for a thermostat for the bedroom air conditioner. I added my a/c after the fact, didn't know that it is set up so it can be added to the duct system so ordered the wrong thing and I didn't know about it until it was already installed. The tech told me that those wires near the safe are for a thermostat had I ordered that type of A/C. As it is, in the winter I am going to have to spend a couple of hundred dollars to have it converted to the ducted version with a thermostat . . . such is life.