Same situation here. SLP98UHV in communicating mode with dying iComfort wifi stat.
However I didn’t spend the money on a fancy XC17 or 21 or 25, I have a simple 13acx single stage non-communicating ac. So my furnace control board has 4 wires in the R i+ i- C to the stat, but the outdoor side is empty. There are two wires coming in from outside going to (i think, i may have forgotten) Y and C on the traditional terminal strip. The icomfort knows the furnace is communicating and the ac is not, so I guess that’s how it energizes only the Y terminal when the icomfort calls for cooling or dehumidifying.
When I pulled my icomfort stat from the wall there are 5 wires, but one isn’t being used.
If I want to switch to an ecobee, will 5 wires be enough? I’m guessing I won’t get to us the ecobee in 2 stage mode with just 5 wires, just single stage and the furnace will be in it’s least useful mode. Being controlled by a single stage stat and using dip switches to use a low burn and high burn setting (compared to variable 35-100% gas valve and variable 35-100% fan speed) and get maybe a couple fan speeds out of it. Kind of like taking a modern 10speed dual clutch auto out of a new car and putting in an ancient 2 speed powerglide lol.I mean it will heat the house but probably be noisy and temp fluctuating.
Is 5 wires enough or do I need more? I was thinking R, C, W,Y1, G. That gives me heat, ac, and fan only right? Then what about dehumidify mode?
As far as the question of converting the furnace to dumb mode from smart mode, I think it ships from the factory with all dips down, and if your installer hooked up to the R i+ i- C terminals then the dip switches are ignored. If you move the wires over to the standard terminals you would have to carefully change several dip switches to set fan speeds, ramp choices, delay, etc. All the things the icomfort does at the stat.
Oh as far as the comment about not having emergency use of the furnace or ac if the icomfort dies completely. I’m pretty sure you could in an emergency, take a cheap thermostat down to the basement by the furnace (well, mine is in the basement), unplug the communicating wires, and wire up your cheap temporary stat to the standard terminals. It wouldn’t be ideal but for an emergency situation at least you could have all the cooling or heating you wanted until you figure out what you want to do permanently.In my case I have a laundry chute in the wall next to my thermostat I could just drop wires down there and still have a cheap temporary thermostat on the main floor.
In fact if it was the middle of the night and the stores were closed, couldn’t you jump R to Y1 to fire up the ac and also jump R to G to run the blower motor? Or maybe the controller board would run the fan itself when you jumped R to Y1. You would have to set some dips maybe to keep the fan from roaring at full speed.