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Electric Heat Thermostats

EBEBRATT-Ed Member Posts: 15,344
This came up on another post so I decided to make a new post to clear some things up ....I hope.

So thermostats used on electric baseboards or or other electric heating equipment "fixed electric space heating equipment" as the code refers to it are required to either have a disconnecting means at the equipment, or a circuit breaker in a remote location that can be locked in the off position. Code section 424.19

The "disconnecting means" has to disconnect all power so 240 volt it breaks both wires.

This is usually a thermostat with an "off" position so that it can serve as a disconnect without having to lock out the circuit breaker.

Now with the advent of digital thermostats (and there are plenty of them available for electric heat) everyone want's them as they offer better control and look better.

That's all fine and I have seen some 1 pole and 2 pole (you can use a 1 pole on a 240 volt load but not as a disconnect)

So the problem and the question is this

So now if you take off an old stat with the "off" position and replace it with a digital stat you have to then provide a locking mechanism at the circuit breaker.

Has anyone found a digital stat (two pole) for electric heat that has some type of off position or switch that is listed to be used as a disconnect?


  • Jamie Hall
    Jamie Hall Member Posts: 22,942
    Can't say I've seen one, @EBEBRATT-Ed -- and in addition, you have to remember that that "off" position has to be a mechanical break on both poles, not just some collection of silicon bits removing the drive to an SCR or Triac...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • pecmsg
    pecmsg Member Posts: 4,696
    That make LOTO devices for breakers. 
  • mattmia2
    mattmia2 Member Posts: 9,469
    pecmsg said:

    That make LOTO devices for breakers. 

    It would have to be permanently installed in the panelboard instead of the usual kind that clips on to the breaker, right?
  • pecmsg
    pecmsg Member Posts: 4,696
    NFPA70E approved LOTO Device. 

    EBEBRATT-Ed Member Posts: 15,344
    edited December 2021
    No. It has to be permanently installed in the panel. That is what I have been getting at. They are specific to the brand of panel.

    110.25 lockable disconnecting means

    "if a disconnecting is required to be lockable open elsewhere in this code............the provisions for locking shall remain in place with or without the lock installed"

  • pecmsg
    pecmsg Member Posts: 4,696
    My breaker LOTO is still approved 

    as far as I’m aware 
    EBEBRATT-Ed Member Posts: 15,344

    It's because it's fastened in place. Any appliance or equipment fastened in place must have a disconnect.

    stove, dryer refrigerator, washing machine, microwave you can unplug which is considered a disconnect.

    Dishwashers and disposals if hardwired need a switch on the wall now, if their cord and plug that's the disconnect.

    Window AC same thing

    Electric water heaters same thing if hardwired a disconnect, unless 50' or less from and in site of the panel which is the basic disconnect rule.

    No one puts disconnects on the indoor half of a mini split but your supposed to it's a
    motor driven appliance

    This was not an issue with the old thermostats as they were two pole and had a positive off position which the code accepted as a disconnect.

    LOTO is legal to work on the equipment but especially for homeowners they want some type of permanent disconnect.
    JUGHNE Member Posts: 11,021
    My AHJ wants the locking device installed before the panel cover goes on.
    Makes it permanent (almost anyway).

    Ed, I did post on the other posting about the HW Pro 7000, DP with off switch,
    3600 watts, digital read out and good +/- 1 degree....it claims.
    EBEBRATT-Ed Member Posts: 15,344

    TY. I will take a look at that.