Not compatible with Lennox variable speed furnace motor

[Bengie_D]

I recently tried to replace my Lennox iComfort smart thermostat with the Nest 4th generation thermostat, and found that the Nest was unable to 'talk' to my air handler's infinitely variable speed controller.  It appears that the Lennox iComfort thermostat generates specific commands to the fan motor telling it how fast it should run based on the difference between the current temp and desired (set) temperatures.

I tried the Nest thermostat because it was 1/2 the price of the Lennox thermostat, but looks like I will have to return the Nest and use the original manufacturer's equipment after all.

[Patrick_Caezza]

@Bengie_D 

You are correct.

The Lennox iComfort thermostat uses a proprietary interface that is incompatible with most third-party thermostats.

[jackmartin61]

It is like you've encountered a common issue with smart thermostats and proprietary systems. Lennox's variable speed technology does indeed rely on specific commands from the I-Comfort thermostat, so many third-party options, like the Manga go Nest, aren't fully compatible. It's unfortunate, but sticking with the manufacturer’s thermostat is likely the best option to maintain proper control over your system.