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thermostat starting ac instead of furnace

kupper
Community Member

I have a 5 wire system coming into my nest thermostat.  I am sure it worked for heating last year.  This fall I turn it on to heat and the ac starts.  If i go to emergency heat the furnace starts properly.  

15 REPLIES 15

Houptee
Silver Product Expert
Silver Product Expert

Is it a heat pump A/C system with the OB wire on the Nest or a regular gas furnace with AC?


Houptee -- NJ Master HVAC Licensed Contractor

kupper
Community Member

Gas furnace with ac 

Houptee
Silver Product Expert
Silver Product Expert

There should only be a w1 wire on the Nest that turns on your heat and no emergency heat wire unless you have a heat pump system.

Can you post pics of the Nest wires and also the wires on your system end so we can figure out what you have.


Houptee -- NJ Master HVAC Licensed Contractor

kupper
Community Member

20221004_163803.jpg

This is the control board 

kupper
Community Member

20221005_160318.jpg

 this is the nest side

Houptee
Silver Product Expert
Silver Product Expert

I dont even see the white wire from the thermostat in the control board pic.  Can you take a better pic of the control board with the wires clearly shown what screws they are on. It is hard to tell from that picture.

And do you know if this is a Heat Pump because they have blue wire in the Nest OB and that is only used for a heat pump system.

Who wired the Nest and the control board? Was it a professional HVAC company or did you self install it?

 


Houptee -- NJ Master HVAC Licensed Contractor

kupper
Community Member

The white wire goes to w1. It was wired like this when we moved into the house few years ago. This is a normal gas furnace with outside ac unit. 

Jeff
Community Specialist
Community Specialist

Hi ,

I just wanted to jump in real fast to see if you saw Patrick_Caezza's latest reply and to see if you were able to get that picture. If you are still needing some help, just let us know and we'll be happy to continue helping.

Thanks,
Jeff

Jeff
Community Specialist
Community Specialist

Hey kupper,

I just wanted to follow up once more to see if you were still needing some help here. If so, just let us know.

Thanks,
Jeff

kupper
Community Member

I reset the whole thermostat from the beginning and it all began to work.

Jeff
Community Specialist
Community Specialist

That's good news, kupper. Let's watch it for a couple of days and see how it works. If things remain stable, we can mark things as resolved. I'll check back in with you in a few days to follow up. If anything else comes up, definitely let me know.

 

Thanks,

Jeff

Princesss
Community Specialist
Community Specialist

Hey there,

 

Chiming in-- have you noticed any changes? Let us know if you have additional questions, otherwise we'll be locking the thread.

 

Best,

Princess

Princesss
Community Specialist
Community Specialist

Hi there,

 

Due to inactivity, I'll go ahead and lock this thread in 24 hours. Feel free to start a new thread if you need assistance with your Nest Thermostat and we'd be glad to assist you further.
 

Best,

Princess

Houptee
Silver Product Expert
Silver Product Expert

Check the white wire is firmly in the Nest terminal as that is W1 heat control wire that turns on your heat when the Nest sends out + 24 volts on the white wire to the control board.

Also check the W1 screw is tight on the white wire on the control board and no wires are touching each other making a short circuit.

You must have 2 stage heating and they used the OB wire and it goes to W2 (2nd stage heating) on control board.


Houptee -- NJ Master HVAC Licensed Contractor

Patrick_Caezza
Platinum Product Expert
Platinum Product Expert

Do you still have a picture of the original thermostat's wiring? If you do, can you post it here?


To ensure that I see your reply, please tag me using @Patrick_Caezza