I have a an apartment from 1980s, so the thermostats are quite old. One of them is Marley MD26 Qmark Electric Line Voltage Wall Thermostat x 3. Plus 2x thermostats that built into the heaters themselves (in two bathrooms).

One of the thermostats - MD26

I'd like to replace those with thermostats that also allow remote control. That would allow to control each heater area individually from the thermostat (current setup), or remotely (eg turn them down when we travel). Thanks for any ideas.

  • To be clear, you have 3 of the MD26 thermostats, plus 2 built in 'stats (are they also controlled by one of the MD26s, or are they standalone), and you want to install a remote control "master thermostat" to override them all?
    – FreeMan
    Jul 11, 2022 at 17:49
  • @FreeMan I want to replace them all, and looking for an option that would have the central control way of access too. thx
    – Tagar
    Jul 11, 2022 at 21:14
  • I'm no expert, but I'm not sure that "a centralized thermostat, that would allow to control each heater area individually" if "each heater individually" means setting them to a different temperature. If you want them all to be set to 72°F, then one would work just fine, but if you want the house at 72° but the bedroom at 68°, then I believe you'll need individual thermostats for each heater. But, I could be wrong. Again, please clarify, and edit your original question with the clarification so everyone sees it.
    – FreeMan
    Jul 12, 2022 at 11:45
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    What voltage are those (many bathrooms are120v) where rooms are 240, what kind of wiring? Black , white , ground? Many older heaters in the PNW only switch one side of a 240 , any idea of how it is wired ? We could provide lots of fluff but without the above info there is not enough info to answer
    – Ed Beal
    Jul 18, 2022 at 20:44
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    Knowing the area can be helpful in some cases Colorado helps , my experience there was only a year long and almost exclusively commercial. Many if 240 their may not be a neutral and most of the electronic controls need a neutral. I use the least expensive thermostat sometimes that is a double pole for 2 separate 240v heaters in the same room only breaking 1 leg so not knowing a bit more about the wiring and type of control makes it hard to answer.
    – Ed Beal
    Jul 20, 2022 at 16:15

1 Answer 1


Ok I did a little more looking, you have standard 240v with ground for the larger baseboards and your wiring will most likely be the same as the PNW.

What you will need will be a line voltage smart thermostat. I have no connection with the company, I found MYSA is NRTL listed Similar to UL.

The info I found appears that MYSA will work on 120 or 240v heaters and had lots of good reviews for pairing.

The connections looked similar to your old fashion line voltage thermostats that the black wire is the supply and the red is the switched out , I did not read all the specs but it was common to use 1 thermostat for 2 heaters 240 normally and break 1 leg for each heater or to provide a quick overview 2 heaters fed by 2 wire 240v Breaker #1 1 white to black of stat the stat red wire to heater the black from breaker to the other heater connection connect the ground. Put some black tape on the white conductor coming from the panel.

Now the second heater from another 240v breaker hook up the same on the remaining black red from the thermostat Remembering to tape the white black. But put the black and white on opposites as breaker #1 #1 or number 1 black on even #2 black on odd to provide 240v for control voltage. This is how most larger rooms were connected to 1 stat

If you have 3 wire-black, red , white, ground coming from the panel exchange the red will be the second hot (unusual) I believe I have seen 3 or 4 ckts 240v with a neutral these were normally also feeding a bathroom (most bathrooms not all) are 120v

As always make sure my instructions match the oem of the brand you purchase but you want a line voltage smart thermostat I saw some that could gang together but they were not UL listed and most want room thermostats for the control.

One base board use both Hots to both blacks.

  • Thanks Ed. The living room has 3 heaters connected to one thermostat, I think I forgot to mention this. Master bedroom has 2 heaters connected to one thermostat. The other bedroom has 1 heater on one thermostat, as well as three other thermostat-on-heater areas (two bedrooms as I mentioned, and one closet area). Not sure if this is adds anything new that changes the conversation here.
    – Tagar
    Jul 25, 2022 at 21:25

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