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JBM HVAC, HVAC Technician
Category: HVAC
Satisfied Customers: 146
Experience:  Self Employed Air Conditioning, Heat Pump, and Gas Residential Installation/Service technician
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I am installing a honeywell pro5000 thermostat to a rheem ac heatpump

Customer Question

I am installing a honeywell pro5000 thermostat to a rheem ac\heatpump unit need wiring info for orange and white wires.old thermostat orange was connected to b no b on new thermostat.
Submitted: 8 years ago.
Category: HVAC
Expert:  JBM HVAC replied 8 years ago.


Can you tell me what wires you currently have attatched to what terminals and what empty terminals you have left?

Customer: replied 8 years ago.
I currently have red to R,yellow to Y.C nothing connected,O|B white,G to green aux nothing connected E to brown L not connected

honeywell connectors L\E\AUX\G\O/B\C\y\R/RC

Wires coming out of wall blue,orange,wht,yellow,red,green,brown
Expert:  JBM HVAC replied 8 years ago.


This website should greatly assist you, if you still are not sure what you are doing, just reply back and i will do my best to explain it to you!

Customer: replied 8 years ago.
I have seen reply before following old thermostats connectors to the new honeywell there is no b terminal on new t-stat leaving me with orange wire not connected I have L,AUX,and C not be ing used on t-stat right now does orange wire connect to one of these terminal??
Expert:  JBM HVAC replied 8 years ago.

O/B is generally the terminal that is for the reversing valve.


Can you please tell me what you have hooked up to what in this format:


Wire Color = Terminal


Red =R/Rc/Rh

Green= G

White = W


Customer: replied 8 years ago.
C= nothing hooked up
aux=nothing hooked up
L=nothing hooked up

I have followed wire from old t-stat outside of the orange wire which went to a B terminal on t-stat there is no B on new t-stat.I am hoping this is correct I would hate to wipe out t-stat.
Expert:  JBM HVAC replied 8 years ago.

This is a regular single stage heat pump system correct? You don't have any backup or aux heat right?

Expert:  JBM HVAC replied 8 years ago.

Its best to follow your honeywell instruction manual for installation but i personally think that Orange should go to O/B and W should go to aux or whatever the instruction manual says is the emergency electric heat. I would just double check the White wire was not previously connected to the common terminal on your last thermostat(or C usually)

Customer: replied 8 years ago.
it does not have an aux or backup heat.
Expert:  JBM HVAC replied 8 years ago.
Your heat pump has to have some sort of back-up heat. If you do not have a fossil fuel as back up it will most commonly have electric resistance heat built into the air handler
Customer: replied 8 years ago.
Where would air handler be located
Expert:  JBM HVAC replied 8 years ago.

The air handler is your indoor unit that has your evaporator and your main Fan in it

Customer: replied 8 years ago.
the unit is located on roof,looking inside unit the blower is inside below the contactors,relay, etc.
Expert:  JBM HVAC replied 8 years ago.

Your ductwork enters your house from the roof?

Customer: replied 8 years ago.
Expert:  JBM HVAC replied 8 years ago.
Ok, so this is a packaged unit. It is just packaged Heatpump with no natural gas combined with it?
Customer: replied 8 years ago.
Yes, there is no gas lines running to unit.I was a little thrown off by that also.
Expert:  JBM HVAC replied 8 years ago.
Thats very interesting, you still must have some sort of backup heat i would think. A heat pump is designed so that every so often on a very cold day it will go into defrost, if you don't have backup heat you would be left without any heat while the unit is in defrost mode. I would still recommend hooking W and white up together while hooking the orange wire up to O/B
Customer: replied 8 years ago.
Looking at t-stat the wiring diagram is set up for either conventional or heat pump if looking at conventional side(upper) the white wire is in the W if looking at heat pump side (lower)it is on the o/b does that help at all it seems they both share this terminal this is why the orange wire is throwing me off.In previous messege old t-stat orange wire was hooked to b there is no b on new t-stst.does this help at all
Expert:  JBM HVAC replied 8 years ago.
Yes that o/b terminal usually stands for orange or blue. Can you look in your manual to see if this is for the reversing valve and if so, look at the wiring diagram for your unit and see if the orange wire is also for the reversing valve. If so then orange should be on o/b
Customer: replied 8 years ago.
according to t-stat manual the o/b is changeover valve I cannot locate wiring diag on unit
Expert:  JBM HVAC replied 8 years ago.

Here is a way we can find out what that orange wire is for. Try running your unit without the orange wire hooked up and see what it does, or actually, doesn't do.


Run it in Heating and Cooling mode

Make sure fan operates in both

Also turn emergency heat on and make sure it works

Customer: replied 8 years ago.
I will do that now
Expert:  JBM HVAC replied 8 years ago.
I will await your reply, i will be in and out for the rest of the night so my response may not be immediate just fyi
Customer: replied 8 years ago.
Nothing is happening upstairs
Expert:  JBM HVAC replied 8 years ago.
I'll tell you what, i'm going to opt out because i'm going to have to leave the office in a short while, so i will let another expert further assist you to get this done. Please stand by for another expert.
Expert:  Mark Henley replied 8 years ago.



B is used for the reversing valve for RHEEM products and a couple of units by other manufacturers, If there is no B terminal it will be the reverse of O in the set up of your thermostat. If you still need help with this stat reply back and let me know where you are at with it.





Expert:  HVACguy replied 8 years ago.
hi i agree with mark . hook to o/b then in the installer setup choose energize valve in heat mode
Customer: replied 8 years ago.
Hello mark,not sure if you received other question,it seems everyone agrees that orange wire will go to o\b that leaves me with the white wire.Is it safe to assume it will go to w2???
Expert:  JBM HVAC replied 8 years ago.

I see that both other experts are offline, so i will try and help you out again.


It should be safe to put it on W if you have nothing there and W2 if you do have something there already. Its safe to do this as long as it is not the common side of the transformer

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