Smart Thermostat - AC only

This may be a dumb question, as I couldn't find this question asked anywhere else. However, when it comes to smart thermostats, can they be used with AC only units? My parents house have baseboard heaters which separate from their AC unit and wasn't sure if Smart Thermostats like Ecobee, could be used to replace AC only thermostats.


Yes, however I caution that you'll need a common wire with almost any WiFi equipped thermostat.

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WiFi thermostats, yes. Z-Wave or Zigbee, it will depend on the thermostat.

Lux KONO models run off batteries or C wire. Honeywell T6 Pro Z-Wave runs off batteries or C wire.

@Shamwedge make sure you read the specifications and requirements for the thermostat you are looking to purchase.


Sorry, I probably should have mentioned that their current thermostat, luckily does have a C wire!

Are there any favorited brands amongst the hubitat community? Just need something fairly simple and straightforward for the parents as far as every day operation goes; I'll be handling the setup portion.

Do you plan on using the thermostat with Hubitat or will it be a standalone device for your parents?

For simplicity, since the t-stats will be for AC only, I recommend something like this:

Since you have a C wire, your choices are pretty much endless.

It has a C wire, but there's also a wire at the W or O/B terminal. Do they have a heat-pump, or is their HVAC system single-stage heat/cool, and not just single-stage cool (i.e. A/C only)?

If it really is just single-stage cool, then the white conductor isn't connected to anything at the other end. Leaving me to suggest that you should confirm that the C conductor (blue) is connected to the C terminal at the air-handler (or the ground side of the 24VAC transformer).


@jkudave It will be configured with the hubitat. Essentially, I'm ok with it being on the techy side as I'm setting it up and will be doing maintenance, but for the every day operation, just has to be straightforward for the parents.

The Lux Kona you mentioned looks pretty, and pretty straightforward.


This is exactly why I wantrd to post a picture of the wiring, just in case something seemed wack-a-doo.

Coincidentally, they're having an AC guy coming out to look at their system for general maintenance. Maybe I'll see if he can confrkm the wiring whiles he's there. However, the AC is strictly AC only as they use baseboard heaters that have their own individual thermostats.

They are fantastic thermostats. I have 2 of the KONOz, Zigbee models. Unfortunately, I had to stop using them due to them continually dropping off my Zigbee mesh after migrating to a C8 hub. They worked with zero issue for years with my C5.

Lux makes the KONOz which are Zigbee, and the KONOzw which are Z-Wave. If you are using a C8 I would advise going the z-wave route.

Since I had the issues with my KONOz thermostats, I have switched to the Honeywell T6 Pro Z-Wave. These are also highly recommended. However, they may be overkill for simple AC control only.

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I actually just got them to replace their old C4 as it was having some weird issues, that just seemed more easily fixed by getting the new C8 while it was on sale. So thanks for letting me know about that regarding the Lux! Z-wave sounds like the better option, plus they have z-wave extender, which is primarily used for their older Schlage Door lock. So hopefully that will add some stability as well.

However, after all this, they just found out they're more than likely going to have to replace their AC unit as it still uses R22, which is apparently now illegal as of 2020.

So this project will more than likely have to be put on hold unfortunately. Thanks everyone who chimed in though!!

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It is only illegal to produce new R-22 refrigerant, and by extension new equipment can't use it either. You can still service R-22 equipment using R-22 stock from everything I have read and heard.

You might be in for sticker shock at the price of R-22 per pound. It will still be cheaper to add a pound or two of R-22 than to replace everything, and that might get them by for a year or two. That said, new equipment is very likely to be a lot more energy efficient, and there are federal incentives to replace old stuff in the ironically named "Inflation Reduction Act" bill from last year.


This is incorrect. R-22 cannot be produced in the US (or imported) as of 2020. However, it is perfectly legal to use reclaimed R-22 to service units that are currently functional (and existing R-22 stock as @neonturbo posted).

There is another option that is fairly popular depending on where they live to continue using existing R-22 compatible condensers and matched evaporators.

And that is to recover the (remaining) R-22 in the existing system along with the pagination oil. And then replace it with R-407c and oil that is compatible with R-407c (along with replacing a few seals and the Schrader valve).

Around about where I live (Louisiana), this will run about $1200-1500 for a 3 or 4 ton system. R-407c is a legal refrigerant, and should minor leaks occur in the future, R-407c can be added as necessary. This is a heck of a lot cheaper and less intrusive than replacing both a condenser and the air-handler.