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New Nest Thermostat - Heater Won’t Shut Off

Jflo
Community Member

I have a Trane XV 90 two-stage gas furnace with a two-zone Honeywell HZ322 control panel.  I purchased a new Nest Learning Thermostat 3D gen and, after following all the instructions, it won’t stop heating during the first test run. Even though it says it is not heating and even when I turn the heat mode to “off”.  The only way to get the heater to turn off is to unplug the Nest from the wall.  

Also, when I set it to test the fan, the heat comes on after a minute. And then it won’t turn off until I unplug the Nest. 

After several experiments with this I find that any time the heat comes on, it won’t stop heating. 

Pictures of my old thermostat wiring and the control panel are below. Per the instructions I removed the jumper wire between the old Rc and Rh terminals, put the red wire in the Nest’s Rh terminal, the W/E wire in the Nest’s W1 terminal, and W2 and G in the corresponding places. What the heck is going on here?  Help!

8091D749-DA0E-4533-BB55-D54848828728.jpeg2ECF71D5-A8FD-4718-B672-54386E7B6357.jpeg

1 ACCEPTED SOLUTION

Jflo
Community Member

Thanks for the delayed response. Having heard nothing here I called Nest for help and they told me my system was wired correctly and I should call a HVAC pro as the HZ322 system may not be compatible with the Nest Learning Thermostat. I didn’t want to pay someone for such basic information so I did some more googling and read reports on other forums that a C wire is needed to power the Nest in this configuration, as otherwise the Nest confuses the HZ322 controller by trying to steal power from the Rc line.  And yes, my control panel does have a C terminal (previously unused) as clearly shown in the picture above. So I connected an extra wire (thankfully my wiring harness had a spare) to the C terminal on the panel and thermostat and voila. It works, all problems solved. 

This is really easy to fix and document, and it is somewhat inexplicable that Nest’s documentation is so unclear on this and their wiring instructions are simply incorrect. May I suggest that someone from Nest correct the contradictory documentation (it does work with an HZ322 controller, but only if a C wire is connected). 

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6 REPLIES 6

Jflo
Community Member

Actually that’s not the right picture of the old thermostat wiring (because it doesn’t show the jumper). Here’s the correct picture. 
B6C20D24-3A85-4BC1-B1C1-3E46697E695D.jpeg

Jflo
Community Member

Any help here?  I’ve read some more and Nest documentation is inconsistent but suggests, maybe, that a C wire is needed to make the Nest Learning Thermostat operate the HZ322 controller.  I can run a C wire from the controller to the thermostat if that’s the way to make it work. It sure would be nice if someone from Google could advise here. 

Jake
Community Specialist
Community Specialist

Hey Jflo,

 

My apologies for the delayed response. I wanted to reach out and ensure you are good to go. Taking a closer look at the pictures and information provided, there is a chance you may need to install a C wire or a Power connector as the device is not properly being powered. This is usually the cause for the system to run constantly. Do you mind me asking if there is a C wire on the HVAC board? If you are unsure, I would advise having a Nest Pro come out and take a closer look. 

 

Best regards,

Jake

GarrettDS
Community Specialist
Community Specialist

Hey there,
Just wanted to jump in here to check to make sure that you saw our response. Please let us know if you have any other questions or concerns as I will be locking this in 24 hours.

Have a great day.
Garrett DS
 

Jflo
Community Member

Thanks for the delayed response. Having heard nothing here I called Nest for help and they told me my system was wired correctly and I should call a HVAC pro as the HZ322 system may not be compatible with the Nest Learning Thermostat. I didn’t want to pay someone for such basic information so I did some more googling and read reports on other forums that a C wire is needed to power the Nest in this configuration, as otherwise the Nest confuses the HZ322 controller by trying to steal power from the Rc line.  And yes, my control panel does have a C terminal (previously unused) as clearly shown in the picture above. So I connected an extra wire (thankfully my wiring harness had a spare) to the C terminal on the panel and thermostat and voila. It works, all problems solved. 

This is really easy to fix and document, and it is somewhat inexplicable that Nest’s documentation is so unclear on this and their wiring instructions are simply incorrect. May I suggest that someone from Nest correct the contradictory documentation (it does work with an HZ322 controller, but only if a C wire is connected). 

View solution in original post

GarrettDS
Community Specialist
Community Specialist

Hey folks,
It looks like we have come to a solution so I'm going to be locking this thread. If you have any other concerns or questions, please feel free to create a new thread.

Have a great day.
Garrett DS