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Nest Thermostat wiring questions

FBS32
Community Member

Hello, first time poster!  I am helping my neighbour to install her Nest thermostat.  It is replacing an old Carrier thermostat.  The Carrier only had two wires connected.  A red wire and a black wire.  I pulled another unused wires out of the wall and found them to be green, brown and blue.  How do I connect these wires to the new Nest?  Red will go to Rh (for power), I assume the green will go to G (fan), but where do I put the brown and blue wires?  Her system is a gas fired furnace (forced air), plus a heat pump for cooling/heating.  I just don't know where to put the brown and blue wires....I don't want to damage her furnace/heat pump by putting the wires in the wrong places?  Any help would be greatly appreciated.  Thanks so much in advance.  Cheers, Colin

3 Recommended AnswerS

CoolingWizard
Silver Product Expert
Silver Product Expert

FBS32, Please provide the model number of the carrier thermostat and upload a picture of the backplate with the wires connected.  You might have a carrier Infinity system.

Thank you,

Ken, The AC Cooling Wizard

NestPro and HVAC company owner

View Recommended Answer in original post

FBS32
Community Member

Mmmm, I will have to return to her house to get the model number in a couple of days.  I will attempt to upload a few photos I took this morning.  THANKS!  

Darn...I get a message that says I 'do not have permission to upload images'   I will try to figure this out.  😀

View Recommended Answer in original post

CoolingWizard
Silver Product Expert
Silver Product Expert

This community app is kind of silly, you have to upload the pictures before you start typing any text. But you cannot upload any pictures until your identification when you set up the account has been verified through your email. I hope that helps.

NestPro and HVAC company owner

View Recommended Answer in original post

9 REPLIES 9

CoolingWizard
Silver Product Expert
Silver Product Expert

FBS32, Please provide the model number of the carrier thermostat and upload a picture of the backplate with the wires connected.  You might have a carrier Infinity system.

Thank you,

Ken, The AC Cooling Wizard

NestPro and HVAC company owner

FBS32
Community Member

Mmmm, I will have to return to her house to get the model number in a couple of days.  I will attempt to upload a few photos I took this morning.  THANKS!  

Darn...I get a message that says I 'do not have permission to upload images'   I will try to figure this out.  😀

CoolingWizard
Silver Product Expert
Silver Product Expert

This community app is kind of silly, you have to upload the pictures before you start typing any text. But you cannot upload any pictures until your identification when you set up the account has been verified through your email. I hope that helps.

NestPro and HVAC company owner

Carrier face placeCarrier face placeInside Carrier thermostat showing only Red and Black wires connected from the furnaceInside Carrier thermostat showing only Red and Black wires connected from the furnaceInside the Carrier thermostatInside the Carrier thermostat

 

Here is the thermostat and wiring I want to change over to the Google Nest thermostat.  The Carrier only has red and black connected.  The other wires: green, brown and blue were tucked in the wall.  The furnace system is a gas fired forced air furnace with a heat pump/airconditioner. Only Red and Black were connected from furnace to the Carrier thermostat.  The other three wires: Green, Brown and Blue were tucked inside the wall.Only Red and Black were connected from furnace to the Carrier thermostat. The other three wires: Green, Brown and Blue were tucked inside the wall.

Jeff
Community Specialist
Community Specialist

Hi FBS32,

I just wanted to jump in real fast to see if you saw CoolingWizard's latest reply and to see if you still needed some help on this or if you were able to get it sorted out. If you are still needing some help, just let us know and we'll be happy to continue helping.

Thanks,
Jeff

Jhonleanmel
Community Specialist
Community Specialist

Hey everyone,

Checking back in should you still have some questions here. Let us know by replying to this thread. 

Best, 
Mel

Hi folks,

I'm just checking in to make sure that you've seen our response. Please let us know if you have any other questions or concerns as I will be locking this in 24 hours.

Thanks,
Mel

FBS32
Community Member

Red and Black wires connected from wall/furnace to Carrier thermostatRed and Black wires connected from wall/furnace to Carrier thermostatInside the Carrier thermostateInside the Carrier thermostateOnly red and black were used for Carrier Thermostat.  The other Blue, Green and Brown wires were tucked inside the wall.Only red and black were used for Carrier Thermostat. The other Blue, Green and Brown wires were tucked inside the wall.Face plate of Carrier thermostatFace plate of Carrier thermostatHere is the thermostat and wiring I want to change over to the Google Nest thermostat.  The Carrier only has red and black connected.  The other wires: green, brown and blue were tucked in the wall.  The furnace system is a gas fired forced air furnace with a heat pump/airconditioner. 

CoolingWizard
Silver Product Expert
Silver Product Expert

Now I see the problem. That current Carrier system is using the a proprietary digital communications with the HVAC system. It cannot be easily switched to a nest system without running a new thermostat cable.  In your case there are enough conductors in the cable probably inside the wall, but we’re gonna have to rewire the HVAC system at the other end of the cable.  If we do this we can switch to the Nest and the Nest can indeed control your home and the library it’s from a single app.

I believe at some point in time a normal thermostat was on the wall and a contractor came in and swapped to this carrier ion system and it’s possible to switch back and start using a Nest Learning Thermostat  if you would like to do so

give me a call 442-222-5995

NestPro and HVAC company owner