Installing Honeywell RTH 7400

Old 04-26-13, 09:06 PM
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Installing Honeywell RTH 7400

I have an old comfortmaker t-stat that controls a heat pump with an electrical heat backup. The wires on the old t-stat were connected to the following terminals:


While installing the new Honeywell Programmable T-stat (which is supposedly compatible with heat pumps), I connected them per the instructors manual as follows

Old T-stat => New T-stat

C => C
Y => Y
G => G
O => O/B
R => R (Jumper to Rc)
W1 => Aux
E => E

* No L or Rc wire from old t-stat; Had an "X" wire without anywhere to put it.

My question is what to do with the extra "X" wire? That manual says to push extra wires back in, but it also says that "X" can sometime be placed in either the "C" or "E" terminals, but I already had a C and an E.

Any thoughts would be appreciated. Thanks!
Old 04-27-13, 06:33 AM
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First, you don't want to use night setback for heating.... You will consume a lot more energy trying to recover temps when using a night setback schedule. We will need more info about your existing thermostat, such as pictures of the sub base and wiring with the thermostat removed from the SB. A model number would also be helpful.

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