Thermostat wiring issue

[urachen]

Hi,

A nest thermstat e was installed last summer by an AC technician.
Today I found there is no aux heat in the thermostat and it only allows heat pump heating. By the way, my house has a heat pump and a gas heater.

I did google search about it and it looks like there is a wiring issue.

What I found on google is that aux heat is white wire. However, when I opened the thermostat, I found the white wire was not connected. I went downstairs and found the white wire from the air handler is not connected to the white wire to the thermostat. Instead, it is connected to the green wire from the compressor that I believe it is a safe ground.
I don't know why they are wired in that way.
Could you please see the attached picture and let me know whether I can just detach the green from the white and connect the white to the white from the thermostat?
Thanks!
DS

 

[LS6 Tommy]

He sold you the wrong t-stat. You have a t-stat for a heat pump without aux heat. You need a W2 terminal to have aux heat. Not sure what he did with the wiring just by looking at the pic. I'd need to see the terminal board connections in the units.

Tommy

 

[urachen]

Thank you for the comment.

 

[jlv03]

Not sure if the thermostat is the wrong one, but it does not appear to match the wiring diagrams you can find online or on the thermostat itself.

https://www.snapav.com/wcsstore/Ext...des/Nest_Thermostat_E_Pro_Installer_Guide.pdf

 

[BD1]

Call tech support for thermostat if instructions are confusing.


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[fitter30]

For emergency heat need 6 wires if the stat needs a common.
R power
G fan
W1 white reversing valve
W2 emergency heat
Y cooling
C common

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