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Old 03-31-2017, 06:14 PM   #1
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This may sound really simple, but would this line stat work to break one leg of a 120/240 volt baseboard heater?


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Old 03-31-2017, 06:15 PM   #2
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Thermostat question?-img_0648.jpg


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Old 03-31-2017, 06:17 PM   #3
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Attachment 102953
This may sound really simple, but would this line stat work to break one leg of a 120/240 volt baseboard heater?


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Yes. The NEC may require that there be a disconnect that opens both L1 and L2 at the same time, but a control thermostat only needs to open one.

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Old 03-31-2017, 06:28 PM   #4
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Yeah normally I get the spdt stat with the four leads but got the wrong one will have to freshen up on nec requirements for resistive loads.


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Old 03-31-2017, 06:35 PM   #5
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Yeah normally I get the spdt stat with the four leads but got the wrong one will have to freshen up on nec requirements for resistive loads.


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You mean you usually get a DPST.
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Old 03-31-2017, 06:53 PM   #6
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Ok. So I read in 424.20(b) that thermostats that do not directly interrupt all ungrounded conductors are not permitted as disconnecting means.
The disconnecting means in 424.19 needs to simultaneously disconnect heater and controller from all ungrounded conductors.
424.19(A) states that the if there be supplementary overcurrent protection the disconnecting means must be within sight.
The stat is not overcurrent protection, but there is a thermal cutoff within the baseboard.
Breaker is around the corner from the stat and heater it controls.
It does not jump out and tell me that it this would be a violation, unless I am missing something.




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Old 03-31-2017, 07:00 PM   #7
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I'd be surprised if the breaker wasn't the disconnect
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Old 03-31-2017, 07:45 PM   #8
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As Inetdog and your instructions on the box both said, if you wire it that way it will electrically work fine, but will not provide a disconnecting means within sight as required by NEC 424.19 (B)(1).
A thermostat that opens all ungrounded conductors AND has a marked OFF position on it can serve as both the disconnecting means and the controller. See 424.20(A) parts 1-4 and 424.20(B).

Edit: Somehow missed your post #6, glad you do your homework!
I'm not sure if I would consider the thermal as "overcurrent protection", as that's more a high limit to prevent a fire (IE idiots piling laundry on the heater) and not really to protect the conductors.
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Old 04-02-2017, 03:03 PM   #9
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As Inetdog and your instructions on the box both said, if you wire it that way it will electrically work fine, but will not provide a disconnecting means within sight as required by NEC 424.19 (B)(1).
A thermostat that opens all ungrounded conductors AND has a marked OFF position on it can serve as both the disconnecting means and the controller. See 424.20(A) parts 1-4 and 424.20(B).

Edit: Somehow missed your post #6, glad you do your homework!
I'm not sure if I would consider the thermal as "overcurrent protection", as that's more a high limit to prevent a fire (IE idiots piling laundry on the heater) and not really to protect the conductors.


Just use that t stat and throw a lockout in the panel.


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Old 04-02-2017, 03:13 PM   #10
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I take it you haven't installed that much electric baseboard. Always had breakers for each room and a t-stat per room unless it was a large room that needed a lot of heat.

Breaker was the means of disconnect, I'd never rely on a thermostat for a means of disconnect.
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Old 04-02-2017, 03:49 PM   #11
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I take it you haven't installed that much electric baseboard. Always had breakers for each room and a t-stat per room unless it was a large room that needed a lot of heat.

Breaker was the means of disconnect, I'd never rely on a thermostat for a means of disconnect.
I have had a few thermostats that would not turn off in the off position
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Old 04-02-2017, 09:31 PM   #12
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I have had a few thermostats that would not turn off in the off position
I've had many that have an off position but one side is welded in place and still passes voltage.
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Old 04-03-2017, 09:41 AM   #13
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We have installed a fair bit of electric heat, with room t-stats. Never had an inspector fail us for this reason. I always thought about though.
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