While installing a programmable therostat, two of the indentification stickers fell off the wires. The wires colors are blue and brown and I don't want to hook them up wrong. The "ports" are E and C. Any help would greatly be appreciated.

Thanks

I understand how heat pumps work, but little more. In a conventional system a blue wire is often used for the common, C? Check at the inside unit controls and see if the blue wire is connected to one of the terminals of the 24 volt transformer. Actually, the brown and blue wires may be connected to terminals marked E and C at the other end. If so, problem solved.