Climatemaster Tranquility 27 dual stage geothermal heatpump

[lowry82]

I have the subject furnance and want to verify compatibility before purchasing a nest thermostat.  My system has C, R, W1, O, Y2, Y1, G and L wires.  Based on the compatibility system it would work by not using the L wire, however some people have identified that Climate Master systems will have faults without this connected.  Can you please address whether this is the case or whether your system is compatiable?

[Patrick_Caezza]

@lowry82 

Can you post a picture of the original thermostat's wiring here?

The L terminal is strictly to turn on a fault LED and normally won't cause a fault.

Here is a link to its manual; if you look at page 38 you will see that the L terminal is not used all the time.

Tranquility 27® (TT) Series - INSTALLATION, OPERATION & MAINTENANCE 

[lowry82]

Thank you for the information...  I tried to upload a photo but it tells me I do not have permission?  I did a little searching and found an identical one (https://www.reddit.com/r/hvacadvice/comments/12by93c/just_moved_can_i_replace_this_with_a_nest/) to mine.  all wires, colors and labeling are the same.  Unfortuantely it doesn't seem anyone gave a solid answer in it.

I have read the attached manual previously, however my current thermostat also displays eror codes and alerts when it is on emergency heat (no LED on thermostat, per se).  Based on all the of other wires purposes, I anticipate this information must be communicated on the L wire.  One other post I had read previously, also said when they switched to a smart t-stat their unit started making a clicking sounds.

If your confident, then I will give it a shot... I just didnt want to drop $300 if there was known issues with compatiability with my furnace.

Thanks

[aperezdeleon]

Hello lowry82,
 
Thanks for reaching out to our community, and thank you Patrick_Caezza, for chiming in.
 
Determining if your system is compatible can be more complicated than it seems. Let's break it down to find the best course of action.
 
Since your system uses standard HVAC wire labels and is wired just like the photo you're referencing, it should be compatible with a Nest Learning Thermostat. According to your system's manual, on page 57, the L terminal is not being activated with any of the heating or cooling stages, so you can ignore it. Ensure to tuck the wire away in the wall and cover it with electrical tape to prevent contact with other wires.
 
However, I recommend contacting one of our recommended technicians as well to determine if your system needs to be rewired or modified for it to be compatible with a Nest thermostat and to ensure a proper installation.
 
Let me know how it goes.
 
Regards,
Angel.

[Patrick_Caezza]

@lowry82 

To upload a picture you need to click on the camera icon at the top of the Replying to box.

I completely understand you do not want to spend money if it doesn't work.

Do you know what brand and model of your current thermostat is?