Lennox SLP98UH + Lennox XC17 Connect with Nest Thermostat Gen3

This post covers the steps I took to set up my Nest 3rd Generation Thermostat with my Lennox SLP98UH and Lennox SX17 furnace. Furnace use to control was Lennox iComfort without wifi. 

Lennox SLP98UH
- 2 stage variable speed gas furnace (indoor)

Lennox SX17
- 1 stage a/c condenser (outdoor)

Overview Step: 

1.                 Turn the AC & Furnace off at the circuit breaker.

2.                 Take the furnace cover off.

3.                 Unscrew the 2 screws holding the circuit cover on.

4.                 Re-wire (change for 4 wire to 7 wire from thermostat to furnace) 

5.                 Setup the Nest Thermostat.

Cons:

- an onboard diagnostic that comes with iComfort thermostat 
- the wire is changed from digital to analog

Initial Wiring

1)    Indoor furnace wire setup

2)    Outdoor furnace wire setup

 

3)    Humidity connection (Indoor furnace)

 

4)    Thermostat connection

 

After Re-wiring connecting with Nest Gen 3 thermostat

Since Indoor furnace wire was hard to explain with a picture,  I did the wiring diagram.

 

1)    Indoor furnace wire setup

Check wiring diagram 

 

2)    Outdoor furnace wire setup (L is not connected)

 

 

 

3)    Humidity connection

Check wiring diagram

 

4)    Thermostat connection

 

I hope this post helps others to change from iComfort to smart thermostat without paying a premium to Icomforst Smart thermostat.