topic Re: Nest Gen 3 Learning on a Trane TAM7 thinks it's dual fuel in Nest Thermostats

Nest Gen 3 Learning on a Trane TAM7 thinks it's dual fuel

N9 — Fri, 24 May 2024 18:43:25 GMT

BLUF: My Nest thinks my equipment is dual fuel when it's all electric single stage with aux heat coils.

How do I change these settings? Is this a result of the wiring?

I bought a Nest Gen 3 and jumped through some hoops to get it to install properly but it is up and running in cooling mode.

It replaced a Trane XL824. The XL824 has no backup battery capability so I would sometimes come home to find that because of a momentary power fluctuation my system would be completely off and would need to be reset at the breaker.

The Trane TAM7 air handler is on a single stage compressor for air and heat, but does have an aux heat coil set.

So I have a Y1 and a W1 and W2. The W2 being the aux heat I imagine.

Also I have a BK wire that on the advice of a different forum member I have connected to the * wiring input to be used to control humidity fan settings. But I don't know where to configure that in the Nest menus.

Any help would be appreciated.

Thanks,

Re: Nest Gen 3 Learning on a Trane TAM7 thinks it's dual fuel

CoolingWizard — Fri, 24 May 2024 18:53:06 GMT

@N9 , can you upload the photo you took of the old thermostat before you removed the wires? From what you are saying you have a Heat Pump system with Auxiliary Heat Strips.
I need to see the photo of the old thermostat.

AC Cooling Wizard

Re: Nest Gen 3 Learning on a Trane TAM7 thinks it's dual fuel

N9 — Fri, 24 May 2024 20:35:13 GMT

CoolingWizard;

Thanks for the response. I don't have a "before" picture but I can provide the diagrams showing what was connected to what.

The first pic is the terminal board for the XL824 thermostat:

Rh and Rc are jumpered on the terminal block. And W2 was connected as well that's why I thought that was for the heat strips. Colored blocks are where there were connections and they are matched to this diagram below:

I'm beginning to suspect that I didn't need to connect W2 at all.

The BK wire is connected to the * terminal on the Nest. I wanted to setup the humidity fan function as somebody on another forum mentioned they did successfully. Not sure where in the settings that's done though.

Thanks again for taking a look!

Re: Nest Gen 3 Learning on a Trane TAM7 thinks it's dual fuel

williamsmithjou — Sat, 25 May 2024 15:04:26 GMT

To adjust settings like configuring the BK wire for controlling humidity fan settings, you'll likely need to navigate through the Nest menus. Look for options related to your county humidity control or fan settings, and you should be able to configure it there.

Re: Nest Gen 3 Learning on a Trane TAM7 thinks it's dual fuel

CoolingWizard — Tue, 28 May 2024 15:08:00 GMT

@N9, on the nest learning thermostat, the Star (*) Terminal

This is a Programmable functions you need to go into the settings to define what you want that to be. This can defined to be Stage 3 heat (W3), humidification (HUM), or dehumidification (DEHUM), 3rd-speed fan relay control.

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AC Cooling Wizard