single or double pole switch for 240V baseboard heater

[William.Deans]

Greetings,

Part A: I have 240V baseboard heaters with the termostat inside the heater. I want to put wall switches in the same place as the light switches so that I can turn off the heaters when I leave the room without getting down on the ground to adjust the thermostat. I know that a single pole switch will work but I wanted to know if there was any reason the code required a double pole switch? Thanks!

Part B: The baseboard heaters are 2000W. If I put 2 of them on the same 20A circuit I am at 83% of the rated breaker capacity (I am using standard Siemens breakers). Do I really need to put each one on its own breaker?

Thank you for your time, William

[RBM]

You can't exceed 80%, so you could use 30 amp wire. A wall thermostat or switch needs to disconnect both hot legs

[peter]

120V circuit has a neutral and a hot; if you stand in a bath tub and touch the two wires one by one, you will get shocked by the hot, and not by the neutral 240V circuit has no neutral; it has two hots (each one is 120V relative to ground). If you touch the two wires one by one, you get shocked twice.

If you switch off only one hot, then the heater wiring is still carrying

120V. This is potentially dangerous.

[William.Deans]

Greetings,

I fail to understand why it is dangerous for the wire to be carrying

120V into the heater. So what? The (optional add-in) integrated thermostat only breaks one pole. Are you saying it is dangerous? Based on your posting alone it appears that if one is dangerous then the other must be as well.

Please explain.

Thanks, William

[William.Deans]

RBM (remove this) wrote:

Greetings,

You cannot exceed 80% of the wire rating or of the breaker rating? I thought it was of the breaker rating? And my real question is: are baseboard heaters considered intermittent loads?

Thanks, William

[Toller]

Do it if you want to; it is neither legal nor safe. With a switch off, there is to be no voltage at a device. With a single pole switch, someone working on the heater will be very surprised. Your heaters could easily be on for hours at a time. Do you think that is intermittent?

Do what you what, but don't hope that people will tell you it is okay.

[Rich256]

What you are saying is true but I expect code requires a double pole. Someone working on the unit would not depend on the thermostat to remove all power but would most likely expect it to be removed by the switch.

Kind of like power to a lamp with a non polarized plug being plugged into a switchable socket. It is possible for the lamp to have voltage even with the switch turned off.

[Rich256]

My mind was somewhere else on that last statement!!! Thinking of the outside of a socket I guess.

[Edwin Pawlowski]

Yes, 83 % is too high.

If the wire is properly matched, it works out to both.

And my real question is: are

What is intermittent about a heating element that maybe on from a few minutes to hours at a time?

I'm glad I'm not your tenant. You seem to want to cheap out on this and potentially cause a serious safety situation. Use the right double pole switch, use the right wiring.

[Jeff Wisnia]

I take it you meant to say, "even with the switch ON THE LAMP turned off"

Jeff

[HeatMan]

I am happy as (insert expletive here) that you are NOT my landlord.

You've asked nearly the exact same question three times. You must be a real cheap person.

FWIW, back when I rented, I (as the tenant) was responsible for the utilities.

[Jeff Wisnia]

He's probably too cheap to convert that apartment to separate metering so the tenant can pay for the electricity, and would then also have an incentive not to waste it.

Or, maybe he's renting an "illegal apartment" in an area zoned only for single family housing and can't do that.

Jeff

[Mark Lloyd]

That reminds me of the way I first learned to connect 3-way light switches. It's considered unsafe because the light can be off and still have 120V connected to it.

[Rich256]

Yeah, but as I posted, I don't know where my mind what when I made that last statement. Immediately after I hit the send button I realized what I had said. With the switch off there should not be any voltage on the lamp.

If plugged into an ordinary socket it could have voltage on the outside rim of the socket.

[Chris Lewis]

According to Toller :

Ah, but it is. Call it crazy, but the NEC (and I believe the CEC as well) permit the use of single pole thermostats with 240V heaters.

I don't like it either, and when installing a heater, I'll use a two pole thermostat.

But, anybody fiddling with the wires of a 240V heater, relying _only_ on a thermostat to shut power off, probably deserves what they get.

As an interesting sidenote: somewhat akin to the special ampacity ruleso for motors, the CEC has special provisions for dedicated electric heater circuits.

While you cannot exceed the 80% rule for the breaker, you can load the wire to 100% of its rating.

In other words, if you have a 15A heater on 120V, you can use a 20A breaker and 14ga wire.

Which suggests to me that the continuous 80% ampacity limit is largely for the breaker's benefit, not the wire.

This doesn't apply to the NEC.