Change lennox icomfort thermostat to nest

[Lexylalas]

There are 4 wires red, white, blue, and black. Will it be compatible with nest

 

[dreed]

I just replaced my Lenox iComfort Wi-Fi thermostat (temporarily as an “experiment”) with the Nest Thermostat.  It was not easy, I had to change a dip switch setting and move thermostat wires around on the control board of my Lennox furnace (SLP98UHV).  I was only able to do this because I have the 66 page installation manual that came with the furnace.  The iComfort thermostat is a “communicating” thermostat.  Are your 2 middle wires ( white and blue in your case) labeled I+ and I-?  I think this is some kind of special Lennox communicating bus that the Nest won’t understand.  In my case the big Lennox manual told me how I can use a “non communicating” thermostat like the Nest Thermostat in place of the iComfort one.  I had to study the manual a bit to figure this out, but it told me what to do.  My iComfort Wi Fi thermostat used only 4 wires just like yours, but to do the heating and cooling function I had to use 5 wires and move them around on the furnace control board.  I’m a retired electrical engineer so was comfortable doing this.  If you aren’t comfortable doing this, your local Lennox pro can probably do it if he/she has the manual for your furnace.  I can tell you for certain that you can absolutely replace a smart Lennox iComfort thermostat with a Nest Thermostat, but you need the Lennox manual to guide you.

I love the Nest Thermostat, but actually like my Lennox iComfort Wi-Fi thermostat better.  It shows me the 5 day weather forecast, etc. and I like that I can adjust the display brightness.  I only did this as an experiment.  I will be using the Nest in an apartment that has a much simpler heat only application.

I hope this helps.

[dreed]

To follow up, here is the wiring of my Lennox iComfort thermostat before I made the changes for the Nest.

 And here is a photo of the Nest temporarily in front of the iComfort mounting plate.

 Here’s a photo of the front of my manual…

 

[dreed]

And here is a photo of page 34 with my notes, this table told me what I needed to know.

 

[newsvendor]

Awesome! I think my iComfort gave out and I'm trying to replace it with a Nest. See photos; my iComfort has an Interface unit between it and the Lennox AC and the old non-Lennox (non-dual-stage) furnace/fan. The Interface has 4 wires coming in from the thermostat and these same 4 go out to the oudoor AC unit (R, i+, i-, C). To connect the Nest, I think I want to entirely bypass the Interface.  I'll connect the 3 R's (from the AC, the furnace, and the thermostat). Similarly I'll connect the 3 C's and the 3 Y1's. And connect the W from the furnace to the W from the thermostat. All without the Interface board. That should work, right? And hope the fan comes on when the AC comes on and when the furnace comes on (I only have 4 wires to the thermostat, not 5, so I don't think I can turn on a continuous fan, unless I run a new 5-wire strand to the thermostat. Although possibly I don't need the C at the thermostat and can instead use that wire to connect the G at the thermostat to the G at the furnace.) Thanks! iComfort InterfaceAC unit with iComfort 

[newsvendor]

OK, the "O" must reportedly swithces it to heat pump (which I don't have), the B switches it back to AC, the L is for some kind of auxiliary (unused in my case?), the W is for "who knows what" :). So I'll connect the 3 R's (from the AC, the furnace, and the thermostat). Similarly I'll connect the 3 C's and the 3 Y's. And connect the W from the furnace to the W from the thermostat. All without the Interface board. That should work, right? And hope the fan comes on when the AC comes on and when the furnace comes on (I only have 4 wires to the thermostat, not 5, so I don't think I can turn on a continuous fan, unless I run a new 5-wire strand to the thermostat. Although possibly I don't need the C at the thermostat and can instead use that wire to connect the G at the thermostat to the G at the furnace.)

[newsvendor]

Seems to have worked as planned!

[MelbaDT]

Hey folks, 

Thanks for sharing your insights and for keeping the Community alive. I appreciate your very detailed discussions here.

newsvendor, glad to hear that you've got it working and welcome to the Google Nest family. 

dreed, thanks as well for sharing to the Community your notes and how you configured your own system — this will be a huge help to others out there who have the same system as yours. 

Lexylalas, you might want to try the detailed suggestions above and see if it works for you. Keep us posted. 

Best, 

Melba

[MelbaDT]

 Hey Lexylalas, 

How's it going? Have you had the chance to try the suggestions above?

Best, 

Melba

[Ryan_G]

Hey there,

Thanks for being here in the Google Nest Community. 

I'd like to bump in here and make sure that you’ve seen our response.
Please let us know if you have any other questions or concerns as I will be locking this thread in 24 hours.

Have a great day.

Best regards,
Ryan