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Google Nest with Rheem Split Unit - Wiring Help Needed

DBNet
Community Member

Greetings...

I have a OLD Rheem AC/Heat system that is so old it has mercury switches!  It still all works great and it is used for our upstairs. Please see photos for wiring and info on the system. (Just need better control than mercury!)

When I used the Nest compatibility tool, it says it is not compatible. The reason stated was that it was a proprietary  system. Yet I have seen that others have been able to connect a Rheem system to a Nest Gen 3. 

Attached a is a shot of the current wiring and shots of the labels for help in this. 

Note that the WHITE wire travels over from W2 to E. 

Any help with how I should wire the Nest Gen 3 would be great.  Thank you kindly.

David

PXL_20220518_163413072.jpgPXL_20220518_163351727.jpgPXL_20220515_182405347.jpg

1 ACCEPTED SOLUTION

Patrick_Caezza
Platinum Product Expert
Platinum Product Expert

Give this a try

Brown - X to C

White - W2 to W2/AUX (set as AUX heat)

Yellow - Y to Y1

Green - G to G

Red - R to Rc

Blue - B to OB

Orange - O to (not used)

You will need to make this change on the heat pump orientation.

  1.  On your thermostat, go to Settings.
  2. Select Equipment.
  3. Select Continue > Continue.
  4. Select Heat Pump.
  5. The Nest Thermostat defaults to an O setting for heat
    pumps. 
    • If the O option is highlighted, select B.
  6. Test your heating and cooling again to make sure the issue is resolved.

 

The Orange (O) wire is for a defrost mode which the NEst doesn't support, so just tape it off

View solution in original post

14 REPLIES 14

DBNet
Community Member

Hello?  Anyone?

DBNet
Community Member

Really, no one can help with this?

Ryan_G
Community Specialist
Community Specialist

Hi DBNet,

 

Thanks for reaching out here in the community and we're sorry for the delay.

 

By looking at the photos, it looks like you have a heat pump that could be compatible with Nest Learning Thermostat. I'd like to verify the connection for the W2 and E. Could you take another picture showing a clearer connection for those 2 white wires?


Also, when you use the online compatibility checker, you could remove the X wire as it is possibly the wire for the display from the old thermostat and we don't need that on the Nest thermostat. 

 

I hope to hear from you very soon. 

 

Best regards,

Ryan

DBNet
Community Member

Hi Ryan...

THANK YOU for reaching out!!!

1st I have to say LOL on the X wire being for the "display".  This is an OLD system with just a slider to set the temp that is then used with mercury switches. So more or less, little metal bands bend as the temp changes and the mercury then slides to make the ON connection.  🙂  

Now getting back to what you had asked.  The WHITE wire comes out of the wall and wraps around W2 and then continues on to E.   I had mentioned that in my post "Note that the WHITE wire travels over from W2 to E."

Hope these 2 photos help. 

Thank you again Ryan!  I hope we can get it to work!!!

PXL_20220523_181002442.jpgPXL_20220523_182526508.jpg

Patrick_Caezza
Platinum Product Expert
Platinum Product Expert

Give this a try

Brown - X to C

White - W2 to W2/AUX (set as AUX heat)

Yellow - Y to Y1

Green - G to G

Red - R to Rc

Blue - B to OB

Orange - O to (not used)

You will need to make this change on the heat pump orientation.

  1.  On your thermostat, go to Settings.
  2. Select Equipment.
  3. Select Continue > Continue.
  4. Select Heat Pump.
  5. The Nest Thermostat defaults to an O setting for heat
    pumps. 
    • If the O option is highlighted, select B.
  6. Test your heating and cooling again to make sure the issue is resolved.

 

The Orange (O) wire is for a defrost mode which the NEst doesn't support, so just tape it off

DBNet
Community Member

Patrick...Thank you kindly for the reply and information.  I will give it a try tomorrow and see what may happen.  Gulp! 🙂 

(Hey, the unit is 27 years old, 2 ton, but still runs the upstairs.  We have a new, 2020, 5 ton for downstairs main living area so I had no issue with that and Nest. The old one surely is not efficient as the new, but hey...it still runs!) 

I'll report back but wanted to say thanks in advance for trying to help.

DBNet
Community Member

Patrick....It works!!!!  This is despite the online NEST compatibility page said it would not! Thank you for your help.  I wired it as you said and also made the setting change mentioned and all seems to work as it should!    

THANK YOU!!!!

David

DBNet
Community Member

Patrick...

Side Question... Any idea why the online compatibility page would say it would not work when it clearly does?  (I mean I have read that it does, but did not find any notes on how until you came along.) 

Thank you.

Patrick_Caezza
Platinum Product Expert
Platinum Product Expert

The online capability checker is only as good as the wiring information you put into it. It doesn't know what the X terminal is or that, in this case, the O terminal isn't to control the heat pump valve.

I have been messing with this long enough to know what-is-what and where to look when I don't know.

Your average layperson has no real need to know stuff like this. You'd be surprised how many HVAC people don't know this type of stuff too. lol

Well I truly do. Thank you for your help! I've been researching and researching and couldn't find anything on it and all I got was the blue wire was a proprietary wire to the manufacturer and therefore wouldn't work. Though I knew I had read that other people had done it, I just couldn't find out how.

So thank you very very much for your help! Now off to learning more about the Nest thermostats and how to best get the savings it possibly can make.  We like to sleep at around 70° and in the daytime we usually run about 76° for the summer heat. We are located in East Tennessee. 1900 ft elevation.  We had just purchased this house, and thus have no idea on the insulation, or otherwise. So they're surely will be a learning curve. Heating it in the winter time, will be another story of course.

But I think you again for your help in making this system work. Now have a Nest thermostat downstairs and one upstairs. Now to figure out what to do next with it.

Thank you again Patrick!  It is people like you that make communities like this possible.

David

 

 

 

 

Ryan_G
Community Specialist
Community Specialist

Hey DBNet,

 

Thanks for sharing your thoughts here in the community.

 

It's great to hear that the recommended wire configuration suggested by Patrick worked. We really appreciate your kind words being shared here on how Patrick helped you and make it possible through this community. We'll keep this thread open for the next couple of days and let us know how it goes with your thermostat.

 

It is really an honor to have your here in the Google Nest community, Patrick. 

 

Best regards,

Ryan

Ryan_G
Community Specialist
Community Specialist

Hey DBNet,

 

I just wanted to follow up and see if you're still in need of help. Please let us know as we would be happy to answer any questions you may have. 

 

Best regards,

Ryan


 

DBNet
Community Member

Hi....

All is good here thus far thanks to @Patrick_Caezza suggestion on the wiring.  So far so good!

Thanks for checking in.

David

MelbaDT
Community Specialist
Community Specialist

Hey there, 

 

Awesome — glad to hear that and thanks for getting back to us. Since everything is working as it should, we'll be locking this thread after a day. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the community.

 

Best, 

Melba