Using Smart Thermostat with In-Wall Electric Heater

My home has a walk-out basement that was completely finished by a previous owner. The lower-level rooms are not on the central forced-air furnace; rather, the two bedrooms and the family room down there each has a King W2424 240V/2400W heater in the wall, each of which is controlled by its own line-voltage thermostat external to the heater. The original thermostats were mechanical (i.e., bi-metallic coil) but I’ve since replaced them with digital. These heaters have a built-in fan to circulate the heated air.

The family room is where the TV for the house is, so it gets semi-regular use, but the bedrooms are seldom occupied. In addition, when we are away for extended periods of time, we often let friends/family use the house. Occasionally the heat is left turned up in one or more of the three rooms, needlessly heating them and running up the electric bill. Not only would I like to be able to automate the heating of these rooms, but also be able to dial them down remotely if someone leaves them at a higher temp.

There are Aube relays which can be used to connect a low-voltage thermostat (including smart ones like Nest) to these heaters, and I’ve also found a few line-voltage smart thermostats.However, especially with the latter, they pretty much all say they’re for use with baseboard and in-floor heating only, and some explicitly say they will NOT work with forced-air systems.

So, my question is . . . why?

The current thermostats, and the ones before them, essentially turn the whole heater on, or the whole heater off. When it’s on, the heating element is working and the fan is blowing. When it’s off, both are off. The only reason I can think of that a smart thermostat wouldn’t “work” would be if these heaters were designed for the fan to keep running for a few minutes after the heating element shuts off, to circulate the residual heat. But that’s not how they work.

So, can a more knowledgeable person clue me in as to any reasons (including safety - especially safety) that I shouldn’t be able to use a smart thermostat with these?

For safety you simply need to understand if the original design of the units allows the element to be on without the fan.

If no, then does the fan always have to be on?

If yes, does it have to extend after? By design.

If the design is as you say, fan on in conjunction with element, then I don’t see why any programmable thermostat wouldn’t work.

I’d stick with some sort of thermostat for greatest safety and control.

The term “forced-air furnace” is used to describe a central heating system in your house using ducts and vents to distribute heat to all different rooms in your house and they usually use low voltage thermostats for control. Most electric thermostat will have this warning on the box so the majority of the people won’t be confused.

Thanks for your comments. The part that makes it a bit confusing is that some wall heaters have blower fans (and sometimes refer to themselves as “forced air”) while others are strictly convection or radiant. So it can be unclear whether they are referring to the ones with the fans or not.

The unit for the upstairs of our house is a forced-air propane central furnace.