Honeywell RTH 7400 Thermostat wiring for Heat Pump (Rheem)


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Old 11-23-06, 11:25 PM
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Honeywell RTH 7400 Thermostat wiring for Heat Pump (Rheem)

I am trying to hook up a Honeywell RTH 7400 Tstat to the existing Rheem HVAC in my house. Currently using Rheem thermostat that came with the house (non-programmeable, using mercury tubes). Heating is provided by a heat pump as well as Natural gas furnace for aux heating (besides the air conditioner for summer). This is the original system installed in the house when it was built 4 years ago. See details on current Rheem connections below. The proposed new connections using Honeywell RTH 7400 are also below with a link to the installation instructions.

The problem is the Blue wire in my current Rheem system. Some other information on the web indicates that Rheem systems have separate O and B wires. For example:

B=reversing valve (heat pump) energizes on heat (mostly just Rheem/Ruud/Weatherking)
O=reversing valve (heat pump) energizes on cool (Most all heat pumps)

In the Honeywell Tstat the O and B terminals are not separate. So what happens to the extra Blue wire? I doubt it can be left unconnected?! Any help is very much appreciated. If the answer is that this Tstat cannot work with this HVAC system then thats ok too. I will return it and find one that does work. Any recommendations? Thanks for the help.

Below are the details on current Rheem connections and the new Honeywell RTH 7400 Tstat.

Current connections of Rheem Tstat:

Wire ----> Connected to -> T-stat Terminal
--------------------------------
Green ---> Connected to -> G
Red -----> Connected to -> R
White ---> Connected to -> W2 and E
Yellow --> Connected to -> Y
Orange --> Connected to -> O
Black ---> Connected to -> X
Blue ----> Connected to -> B

Proposed connections using Honewell RTH 7400 Tstat

Wire ----> Connected to -> T-stat Terminal
--------------------------------
Green ---> Connected to -> G
Red -----> Connected to -> R (jumper to Rc)
White ---> Connected to -> Aux (jumper to E)
Yellow --> Connected to -> Y
Orange --> Connected to -> O/B
Black ---> Connected to -> C
Blue ----> Connected to -> ??

Honeywell RTH 7400 Installation Instructions (http://customer.honeywell.com/Techlit/pdf/69-0000s/69-1900ES.pdf)
Pages 10 & 12 for wiring reference. Pages 18 & 19 for System Setup of options 170, 180 and 190.
 
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Old 11-24-06, 09:26 AM
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Wink

B=reversing valve (heat pump) energizes on heat (mostly just Rheem/Ruud/Weatherking)
O=reversing valve (heat pump) energizes on cool (Most all heat pumps)

You have it right in the above. On the tstat You can only use one the B or O wire to the O/B
Just tape off the other Id say run down where the O wire goes and where the B wire goes.
 
 

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