Need help with Nest 3rd gen thermostat installation

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Old 06-27-20, 03:44 PM
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Need help with Nest 3rd gen thermostat installation

I need help to install my Nest (3rd gen) thermostat.
My brother in-law installed it, but I donít think it is wired correctly.



Hi, I donít know if itís wired correctly, because the ac doesnít stay cool for long. After a while, it just blows out hot air. Please help. Thank you in advance.
 

Last edited by PJmax; 06-27-20 at 06:46 PM. Reason: resized pic
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Old 06-27-20, 04:16 PM
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The nest wasnít working properly for 3 weeks or more so I got an ecobee smart thermostat and still need help with installation because I think the wiring is off with the black and blue wires.
 
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Old 06-27-20, 06:39 PM
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Where do the black and blue terminate on the other end?
What did they attach to?
I suggest rethinking the nest and/or staying with the Ecobee. The nest is an extremely poor product.
 
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Old 06-27-20, 06:48 PM
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Welcome to the forums.

If your system was producing A/C..... it is more than likely wired correctly. Based on what I see the black was the emergency heat line. In order for it to be used with the nest then * must be programmed as emergency heat.

It may not be a thermostat problem. It may be a problem with the outside condenser.
If you switch over to the ecobee..... the black wire gets taped off.
 
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Old 06-27-20, 07:12 PM
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Thanks so much for the replies.

Is this the correct wiring?


 

Last edited by PJmax; 06-28-20 at 10:24 AM. Reason: resized pic
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Old 06-27-20, 07:32 PM
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Yes, Iím beginning to think something else is the problem and may not be the thermostat since the ac doesnít blow cold air for long.
 
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Old 06-27-20, 07:34 PM
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What model ecobee is that.
 
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Old 06-27-20, 07:58 PM
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I believe it is the 5th gen.
 
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Old 06-27-20, 08:02 PM
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Did you replace the thermostat attempting to solve a problem you were having?
 
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Old 06-27-20, 08:06 PM
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Yes.... the wiring is correct.
You do need to tell the thermostat that you are using an air to air heat pump with back up electric heat.
 
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Old 06-27-20, 08:35 PM
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Yes, my ac wasnít blowing out really cold air for long periods of time about a month ago, so I switched to the nest first then ecobee. It kept cold for awhile, but is now having the same issue as before. It starts coming out really cold then decreases and can never reach set temperature.
 
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Old 06-27-20, 09:13 PM
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Ok, what diagnosis did you do that pointed to the thermostat being the issue? Or did you change it hoping that would be the problem?
 
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Old 06-28-20, 07:41 AM
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I donít know anything about HVAC. My brother in-law suggested a month ago that I change my thermostat because he had the same problem with his ac but after changing his thermostat, his ac worked well again.

He said he wasnít too sure that he installed the nest wiring correctly which alerted me that it may be the problem still.
 
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Old 06-28-20, 07:49 AM
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My first original thermostat was an old Honeywell, that couldnít keep the ac running constantly and kept turning off on its own but it never blew out hot air, only cold. Then after my brother in-law installed the nest, it wouldnít turn off by itself anymore, which is good except that hot air would blow out after a while.
 
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Old 06-28-20, 07:56 AM
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It’s a bad idea to change parts without troubleshooting the problem first.
You’ll have to use your meter to start troubleshooting. Is the condenser starting every time there’s a call for cooling? Is the reversing valve being powered properly? Do you have Rheem/Rudd equipment?
 
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Old 06-28-20, 04:25 PM
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I have the Lennox system.
 
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Old 06-28-20, 04:32 PM
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The condenser starts and stays running until I turn off the ac.
 
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Old 06-28-20, 04:37 PM
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Does the condenser run when the unit isn’t cooling?
Is the compressor running all the time?
 
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