Thermostat for King Electric Hydronic Heater

dt123

I would like to replace my old radio dial King 859M thermostats. The heating system does not shut off when the set point is reached, turning the house into the Bahamas. I'd like to replace with digital programmable thermostats. Does not need to be smart/wifi connected, just programmable.

King Electric of course recommended their own thermostat (HWP120) but it's so ugly and I've read terrible reviews. A local heating company recommended the Honeywell TL8230A1003. However when I installed it myself it didn't work. I had an electrician come by and he said I needed a 120v thermostat. Does anyone have a recommendation?

About my system:

* 5 King Electric in wall hydronic heaters. Model H612. All in different rooms controlled by individual thermostats.

* Current thermostats: King 859M high voltage thermostat

* Rinnai RL75i tankless water heater

Jamie Hall

That Honeywell is the correct thermostat for that application — in terms of voltage. It must, however, be installed and wired exactly as directed. I do not have the directions for it handy, but there is a chance that it may not be possible to use it — it may require that the neutral be present in the box, or that the two hots be on opposite sides. If this is an older installation, either of these possibilities may be the case.

The King you had is still available, by the way.

If the problem is that the box isn't wired correctly for 240 volts — two separate hots and a neutral — the electrician is correct.

Kaos

Jamie is in the right ballpark. You need the 120v thermostat like TH115-A-120S. This does require a neutral in the box.

You won't be able to use any regular programmable baseboard thermostat that doesn't require a neutral as those need more minimum load than your fan coil will provide.

hot_rod

Some of the radiant electric systems have nicer 120 or 240 v stats

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