Nest wiring to replace Lennox icomfort

[Starlord]

I currently have a Lennox I comfort and wondering how to wire the learning Nest (ver 3). Attached is current base plate and thermostat wiring (C, R, l+,l-)…

 

 I ran into compatibility issues with Nest Ver 1 and hoping the latest ver. works out. Any guidance appreciated.

[Houptee]

You need to go to the furnace and there are screw terminals with standard thermostat labels next to the I+ I- terminals.

To use a Nest or any regular thermostat you have to move the wires off the I connectors over to the screw terminals.

They should be labeled R Y G W C etc.

You will lose the advanced features of the iComfort thermostat tho since it is made to work with that system.

[Starlord]

Thanks for the reply. How do I know which of the  screw terminals to use in place of icomfort. I have two stage heat and AC and two thermostats and assuming the same solution for both.

[Houptee]

Take cover off the furnace and you will see the thermostat wires going to screws marked I+ I-.  and then next to where they are now are standard terminal screws in a row.

Take a pic and post it of the furnace wire connection screws and we can guide you where to put each wire.

[Starlord]

Attached is the board wiring. A lot  going on here. Note I have two (upstairs and downstairs) systems. This is downstairs.

 

 

[Houptee]

OK so now look on the door you took off and it will show wiring diagram decal, or if you still have the manual laying around for the furnace it would be in there also.

It should show Thermostat wiring for using a standard tstat and going directly to the screws with the yellow decal labels.

It looks like you have a 2 stage heating (w1 and w2 screws) and also 2 stage cooling (y1 and y2 screws).

The outdoor unit and indoor unit communicates on the i + and i - wires and with the Icomfort thermostat.

So if you go with Nest you will not have all the same features.

[Starlord]

Here is what I have, so generally, just make sure that the wires labeled on the board are connected to matching terminal on Nest? Same for upstairs unit? And disregard all icomfort terminals? Should I keep the “outdoor” icomfort wires connected?

 

[Houptee]

You have to have 7 wires in the thermostat cable going to the Nest per the wiring diagram.

See on the left of the wiring diagram it shows the thermostat wiring as dashed lines.

You have 2 stage heat and 2 stage cooling system.

And the wiring for the outdoor has to be moved over to the screws Y1 Y2 and C (it shows L but in the notes on the wiring diagram it says L is only needed for icomfort )

[Houptee]

If the existing thermostat cable does not have 7 conductors at the Nest then you would have to run a new thermostat cable to get it to work with this system. You can buy thermostat cable at home depot and lowes. 8 conductor cable is what you will find so one will be a spare not used conductors.

[Starlord]

Thank you! It’s making sense, so should the outdoor board on the tower have similar Y1,Y2,C?  And assuming indoor thermostat and outdoor unit share these coccnections on the board? Thanks, huge help probably to more than just me! There is hope in installing the NEST.

the cable at the indoor thermostat, once icomfort is removed, has enough conductors to complete wiring.

[Houptee]

Yes outdoor unit will have Y1 Y2 C and L but L not needed. Make sure you match up the colors the same as the indoor connections to Y1 Y2 C.

There will be 2 wires indoor on these screws coming from the Nest and as shown in the wiring diagram the double dashed lines on Y1 Y2 and C

[Starlord]

Okay, checked for outside unit board, box on left is locked by power company, right one is power, where would I find said outdoor panel?

 

[Jhonleanmel]

Hey folks,

Houptee, appreciate your helpful response. 

Starlord, I suggest reaching out to a Nest Pro to properly setup your HVAC system and wire them correctly to your Nest Thermostat.

Best,

Mel

[Jhonleanmel]

Hey there,

Checking back in should you still have some questions here. Let us know by replying to this thread. 

Best, 
Mel

[EmersonB]

Hello everyone,

Just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, I would be happy to keep it open. If there's more we can do, just let me know.

Thanks,
Emerson

[Houptee]

Usually the Thermostat wires follow the lineset pipes for the freon, then go inside the unit and attach to screw terminals same as in the furnace.

So you need to remove the cover to access the terminal screws and relocate them onto the Y1 Y2 and C screws (make a note of the colors used so they match up in the furnace.

That power co box has nothing to do with the thermostat wiring its for them to shut off the ac during peak demand on the power grid.

[EmersonB]

Hey natopigro,

Thanks for sharing this visual information Houptee.

@Starlord were you able to read what Houptee has shared above? In case you have an update, you know where to find us.

Regards,
Emerson

[Jhonleanmel]

Hi folks,

Chiming in to see if you still need assistance with this. Let us know if you have additional questions ― we'd love to help.

Best,
Mel

[Jhonleanmel]

Hi everyone,

I'm just checking in to 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 after 24 hours.

Thanks,
Mel