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No heat after installing Nest learning Thermostat

Mrperry75
Community Member

After installing my Nest Learning Thermostat I am only getting cold air from my vents and house temperature drops. I wired the thermostat according to the diagram on the screen yet I am cold! Please help?

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18 REPLIES 18

Houptee
Silver Product Expert
Silver Product Expert

Looks like you have a Heat Pump system.

Do you also have Auxiliary heat? Maybe a gas furnace for backup heat or is it electric emergency heat ?

Do not use any jumper wires on the Nest (your old tstat has jumper on white).

Put White wire in W1 on Nest.

Do you have the OB wire and the C wire connected to Nest?


Houptee -- NJ Master HVAC Licensed Contractor

I do have the O/B wire and the C wire connected. I do NOT have a jumper wire connected.

I do have a Heat Pump system. No gas furnace, all electric. I also have Auxiliary heat And electric emergency heat.

CoolingWizard
Silver Product Expert
Silver Product Expert

You old thermostat has the Emergency and Secondary heat wired together. You only have Heat pump heat and auxiliary heat.

Ken, The AC Cooling Wizard

NestPro and HVAC company owner

Houptee
Silver Product Expert
Silver Product Expert

Some heat pumps the OB wire has to have 24v output for heat and some need 0 volts on the OB wire so you can go into settings and change the OB output.

Go to this link and see #3 read the instructions to switch the function of the OB wire output and see if this gets the heat to kick on.

https://support.google.com/googlenest/answer/9257086?hl=en#zippy=


Houptee -- NJ Master HVAC Licensed Contractor

Well I did exactly what you suggested by changing it to B. The system continued to turn on for a few seconds then shut off. It did this numerous times. Finally I charged it back to O.

Houptee
Silver Product Expert
Silver Product Expert

Was the system running in cool mode right before you changed the OB setting?

If it was running you have to wait for around 20 mins with the system off so the freon gas pressures in the system equalize before it can switch to heat.

Maybe turn off the system wait 20 mins, and try to change OB again then turn on in heat mode.


Houptee -- NJ Master HVAC Licensed Contractor

CoolingWizard
Silver Product Expert
Silver Product Expert

The system has a safety interlock that does not allow the system to switch from cooling to heating back to back. You must wait a minimum of 5 minutes before changing modes.

Ken, The AC Cooling Wizard

NestPro and HVAC company owner

CoolingWizard
Silver Product Expert
Silver Product Expert

Your HVAC system is a Heat Pump with Electric Heat Strips. Your Heat pump control wire is Blue, the compressor control wire is Yellow, The Blower Fan is Green wire, Your Power IN is Red wire and your Power Common is Brown wire. Your white wire is connected to both Emergency Heat and Secondary Heat. Your Nest set up should be:

Primary Heat: Heat Pump, Forced Air

Secondary Heat: Electric, Forced Air

The heat Pump reversing valve is controlled by the O/B (blue wire). Now, some heat pumps are default Heat Mode, and some default to Cooling mode. The O/B wire, when energized, changes the mode. so, it will be change from Heat to Cooling or changed from Cooling to Heat. The nest will allow you to change the O/B function. You set it to energize for Heat, or to energize for cooling. If you have set your equipment type correctly, and as you say, heating is cooling, go into to equipment settings and change to current O/B mode to the opposite. Then retest the heating system. BTW, if it is currently programmed backwards, put it in cooling mode and you should get heating.
Your wire setup on the Nest will be :

RC is Red Wire

C is Brown Wire

Y1 is Yellow Wire

O/B is Blue wire

G is Green Wire

AUX is White Wire

Ken, The AC Cooling Wizard

NestPro and HVAC company owner

I tried what you said. I am still not getting heat. I will return the Nest and purchase a traditional thermostat. 

CoolingWizard
Silver Product Expert
Silver Product Expert

Mr. Perry, please be specific, and tell me exactly what you did to test. And how about posting a picture of how you have the nest backplate wired so we can make sure you wired it correctly.

Ken, AC Cooling Wizard

NestPro and HVAC company owner

EdwardT
Community Specialist
Community Specialist

Hi folks,

 

@Houptee and CoolingWizard, thanks for the help!

 

@Mrperry75, how's it going with your Nest Thermostat? Still need our help?

 

Thanks,

Edward

Yes. I am still not getting any heat after installing the thermostat. At this point, I am just going to return and get a refund. Worst piece of …I’ve ever purchased!

CoolingWizard
Silver Product Expert
Silver Product Expert

You can certainly do whatever you wish. In my years of installing and configuring these Nest thermostats, I have never encountered a situation where the Nest Thermostat did not operate properly when initially installed. I have been called back to homes where the customer states it is not working and In 100% of the callbacks we have discovered that the customer began changing the thermostat and as a result created the problem that caused the heating not to work or the cooling not to work properly. All we do is reset the thermostat, configure it properly and put them back in service.

I also find on this public forum, that many people who report a problem, do not provide the necessary information for us to help them the best. Customers who call on this forum for help should immediately upon opening the ticket upload the configuration of their thermostat, upload a photo of the back plate of the old thermostat and a photo of the back plate of the nest thermostat I don’t know why that logic fails over and over.

Ken, The AC Cooling Wizard

NestPro and HVAC company owner

EdwardT
Community Specialist
Community Specialist

Hi folks,

 

@CoolingWizard, thanks for the help as always!

 

@Mrperry75, thanks for the update. We're sad to see you go. We hope we can make it up to you in the future. Let me know if there's anything else.

 

Thanks,

Edward

EdwardT
Community Specialist
Community Specialist

Hi Mrperry75,

 

It's me again. I wanted to check back in to see if you have other questions and concerns. Feel free to let me know if you do. 

 

Thanks,

Edward

I had a professional to install it correctly. No questions or concerns. 

Jhonleanmel
Community Specialist
Community Specialist

Hey there, 

Mrperry75, awesome — glad to hear that your issue is fixed. It looks like we can consider this one complete, so I will lock the thread shortly unless I can help out with anything else. 

Best, 
Mel