NEST thermostat to control Trane XL15c Heat Pump

[DeanArizona]

My existing wiring set up is G R C Y1 W1.  I am considering a purchase of Trane heat pump model XL15c (single stage compressor with two stage fan).  (1) Is it true that the NEST thermostat can not control this model because the NEST will only operate a fan that has a single speed?  (2) Will I need to add a second wire (G2 or G3?) in order to operate the XL15c?

Any assistance on this subject would be greatly appreciated. Thanks.

[Patrick_Caezza]

Only the Nest Learning Thermostat and the Nest Thermostat E are compatible with multiple fan speeds. They are not compatible with variable-speed fans.

The Trane XL25c looks to be a ductless system that does not have the required 24V thermostat interface. This means none of the Nest thermostats are compatible with it.

Trane might have an adapter you can install, but I don't know.

[DeanArizona]

Patrick,

Thank you for the response. Are you confusing the Trane XL15c that I am considering buying with the XL25c? The XL15c is a roof mounted packaged unit in a heat pump design.

[Patrick_Caezza]

My bad. I searched, and the links to Trane's document sent me to the wrong system.

The Google Nest Thermostat is a basic entry-level thermostat that doesn't support anything other than basic HVAC control.

So the answer to your question is, no, it will not work with a two-speed fan unit.

The Nest Learning Thermostat, 3rd Gen, or the Nest Thermostat E will work.

The number of wires you currently have will not be enough for the new unit, and you should have them install an 8-18 thermostat cable which should cover all options.

[Jake]

Hey DeanArizona,

Thanks for the help Patrick_Caezza.

I wanted to check in and see if you managed to see Patrick_Caezza's post. Please let me know if you have any questions from here. I would be happy to assist, and make sure you are good to go.

Best regards,
Jake

[DeanArizona]

Thank you.  My research shows that I need to tie in a Venstar add-a-wire accessary to increase the number of wires from 5 to 6 in order for the thermostat to operate a two stage compressor (Trane model #XL15c).  In my original post I mistakenly stated that the Trance XL15c heat pump had a single stage compressor.  From what I have learned, the NEST learning thermostat requires a 6 wire connection to operate a two stage package unit.  Thanks for the guidance.       

[zoeuvre]

Hi DeanArizona,

Thanks for letting us know, and I appreciate you checking that for us. Once you have an update, please let me know as I would be happy to assist, and make sure you are good to go.

Thanks for your help here, @Patrick_Caezza and Jake. 

Best,

Zoe 

[Dan_A]

Hey there,

I wanted to follow up and see if you still need help. Please let me know if you are still having any concerns or questions from here, as I would be happy to take a closer look and assist you further.

Thanks,

Dan

[Dan_A]

Hey there DeanArizona,

We haven't heard from you in a while so we'll be locking this thread if there is no update within 24 hours. If you need assistance or want to discuss topics, feel free to start a new thread.
 

Cheers,

Dan