Replacing Cruisair SMX ir thermostats

[tnjet]

I'm getting increasingly fed-up with using the SMX ir thermostats in my Marathon. My buttons are starting to fail. I know I can buy replacement keypads, but want to go in a different direction. Has anyone successfully swapped out the thermostats with something more usable? Preferably looking for WIFI control while away from the coach. I have full time WIFI/Internet, so thats not an issue. Nest would be great. Anything? Anyone?

[Hoffman]

I looked at the idea briefly and not sure it will work. The industry standard wiring makes it possible to swap thermostats, but the SMX does not use standard wiring, so i dont see how to make a replacement unit work.
At least on my coach the SMX also controls the cub heaters and Webasto. I don't see how to integrate those functions into a standard NEST (or similar product).
If you do, i'm interested in how.

[tnjet]

Well....if your coach is like mine, I have a switch that lets me toggle between Cadet (120v) electric heaters and the Webasto (12v) heat exchangers for heat. Whichever one you select by button is the heating system that you get. Both of these run on the Aux Heat function. NEST has an aux heat function built in, so I think that would work. The NEST is 24 volt where I think the SMX ir is 12 volt, but that's easy enough to deal with.

The one thing I can't quite get my head around is the variable speed fans on the roof airs. NEST will handle two speed fans, but there would have to be an interface to adapt from 2-speed fan to variable speed fan.

I live in a warm climate (most of the time) and have found that setting my fan speeds to max for cooling is the best program. The way the SMX is set-up by default is to lower the fan speed more and more as the actual temperature gets closer and closer to the set point. I find the A/C's just sit there and grind as the airflow is reduced and it struggles to satisfy the set point. Running max fan (on manual) while cooling allows the A/C's to act just like your home air conditioner. Temp gets hot, A/C's come on with full fan, air gets cooler, A/C's quit and go off. The units run much less this way.

I don't really see the point of running the roof airs for heating. I know they are capable of it, but heat pumps get much less efficient as the outside temp drops. I would just as soon run the Webasto.

Anyway......looking for someone who has made the conversion.

[Gil_J]

Of course anything is possible. Marathon's Crestron control system with the Cruisair controllers will be a challenge if you want to preserve Crestron control. You might want to consider the new MicroAir thermostats, if you don't need Crestron control and you want to segregate one of your aux heat options or come up with a relatively easy to develop interface.