Hello, I'm brand spanking new to this group. This is my first question here.

I'm switching from an oil furnace to baseboard heat. I will allow 3750w per circuit. So I need to understand how to wire this. For example: one circuit is for 3 bedrooms. Each bedroom will have a 1250w heater and a wall mounted thermostat. How do I wire this? Can someone tell me the wiring sequence from the breaker to the end? Thanks.

This is one of those things that you NEED to hire an electrician to do...

I know that. But I want to know from someone here how its done.

I'm actually an industrial electrician, but without any residential experience and learning this in school many, many years ago, I don't recall the best way to accomplish this task.

I'm actually an industrial electrician, but without any residential experience and learning this in school many, many years ago, I don't recall the best way to accomplish this task.

Ok... then you aren't exactly the average homeowner... and that does make a HUGE difference

What's the difference? If you are an electrician you should know how to wire a circuit.
Are you seriously asking for detailed wire for wire instructions on how to wire this?

As an industrial electrician, I have spent my full career troubleshooting motors and dealing with instrumentation process measurement. Can we get back to my original question? Thanks.

Then I suggest you get a few good books on home wiring.
Asking for instructions on what wire to connect to what is dangerous ground. Every installation is different.

Apart from the ongoing debate of your abilities, what exactly are you trying to accomplish? Have you applied for and received a permit for this work?

What is your incoming service?

Are the heaters 240 volt or 120 volt?

Do you have enough space in your panelboard for the number of circuits you are going to need?

Have you considered switching to an HVAC (electric forced air) system rather than using space heaters?

How are you planning on getting the wiring from your panelboard to the baseboard heaters and theromostats?

What are the required ampacities for each circuit?

What "type" of conductors are you planning on using?

Will you be running the wiring inside of conduit?

This is my plan.

12/2 red and black from a double pole 20 amp breaker in the panel to the first t-stat box. Pigtail the black to one side of the single pole t-stat. The other side of the t-stat will be black to the heater. The red from the heater coming back up will be joined to the other reds in the t-stat box. Then I will continue to the next t-stat with my 12/2 red and black and do the same procedure. I have allowed a max of 3750w per circuit, as per code. My panel is 200 amps with plenty of space.

So, tell me what's wrong with that?

Apart from the ongoing debate of your abilities, what exactly are you trying to accomplish? Have you applied for and received a permit for this work?

What is your incoming service?

Are the heaters 240 volt or 120 volt?

Do you have enough space in your panelboard for the number of circuits you are going to need?

Have you considered switching to an HVAC (electric forced air) system rather than using space heaters?

How are you planning on getting the wiring from your panelboard to the baseboard heaters and theromostats?

What are the required ampacities for each circuit?

What "type" of conductors are you planning on using?

Will you be running the wiring inside of conduit?

donf,
Permit obtained.
My service is 200a.
240volt heaters.
Panelboard has room for this.
I will wire from the open basement up the walls to the main floor.
3750w is the max possible on a 12/2 circuit 20a breaker.
12/2 red and black heater wire NMD90. Standard house wire for heaters.
No conduit needed.

Well to begin with, because you are using multi outlets on the same circuit, the allowable amperage is only 80%. That means you have 16 amps available to you.

240 X 16 = 3840 Watts max. You are planning to use 3750, that's cutting it awful close for my taste.

donf, this in standard practice in the trade. 3750w is normal. Are you an electrician?

Now, back to my wiring method plan. Does anyone disagree with it?

Well it seems to me that you want to do exactly what you want. Why ask a question if you don't want an answer different from what you want?

And by the way, heaters are considered to be a continuous load (on for longer than 3 hours) so you need to take the 3750 and multiply by 125%, Which means the load will be 4688 Watts. Now this puts you at 19 amps on a circuit that allows only 16 amps.

Oh wait a minute, you know that because you are an industrial electrician.

Yes, I am an electrician (not licensed). I also teach Basic residential wiring aand edit college level electrical textbooks.

3750w is the max possible on a 12/2 circuit 20a breaker.

, because you are using multi outlets on the same circuit, the allowable amperage is only 80%.First let's clear up some common misconceptions. In the US, the above is not true for most circuits. In a residence this mystery 80% rule does not apply to receptacle circuits or even most lighting circuits.
The maximum load on a 20A circuit is 20A, or 4800 watts if used at 240V.
Also, there is no multi-outlet 80% restriction either.
If you think I am wrong please provide the code section.

Now... with regard to electric baseboard heat in question, the NEC does in fact require this to be considered a continuous load so the 80% restriction does apply. I believe Canada is the same (the OP is in Canada).
Don is correct there in that a 20A 240V circuit can be loaded to 3840W. The fact that 3750 is so close to that only means milkman is being efficient with these circuits. So what if it is close to the 80% limit? I would do the same thing. Even if it were 100% of the circuit. Just how often do you think every heater will be on at the same time for more than a few minutes?

Don, 3750 watts is the optimal number for this circuit. It puts him at just over 14A, not 19. I think you made a bit of a math error there.


Milkman, what you propose seems fine IMO.I would wire the feed to the thermostat then to the heaters. Use large enough boxes that you can have a feed-in, feed-out and switch legs down to the heaters at each thermostat.

Stan, thank you for being direct with your answer. This is all I ever wanted, someone to double check my plan for me.

Just make sure of your box fill. I know your rules are more stringent than ours, like you count wire nuts and we don't.

Stan,

The answer will be directly on the breaker. Unless the breaker is listed for 100% usage, you must allow for the 80% usage.

I'll go dig through the code book and see if I can find it or not. Just for grins, I'll use the 2014 edition.

The answer will be directly on the breaker. Unless the breaker is listed for 100% usage, you must allow for the 80% usage.I wish you would find this because I have never heard this in my life. At least not in the 30 years I've been doing electrical work.

For giggles here is the 2011 NEC text on this.


210.23 Permissible Loads.

In no case shall the load exceed the branch-circuit ampere rating. An individual branch circuit shall be permitted to supply any load for which it is rated. A branch circuit supplying two or more outlets or receptacles shall supply only the loads specified according to its size as specified in 210.23(A) through (D) and as summarized in 210.24 and Table 210.24.

(A) 15- and 20-Ampere Branch Circuits. A 15- or 20-ampere branch circuit shall be permitted to supply lighting units or other utilization equipment, or a combination of both, and shall comply with 210.23(A)(1) and (A)(2).

Exception: The small-appliance branch circuits, laundry branch circuits, and bathroom branch circuits required in a dwelling unit(s) by 210.11(C)(1), (C)(2), and (C)(3) shall supply only the receptacle outlets specified in that section.

(1) Cord-and-Plug-Connected Equipment Not Fastened in Place. The rating of any one cord-and-plug-connected utilization equipment not fastened in place shall not exceed 80 percent of the branch-circuit ampere rating.

(2) Utilization Equipment Fastened in Place. The total rating of utilization equipment fastened in place, other than luminaires, shall not exceed 50 percent of the branch-circuit ampere rating where lighting units, cord-and-plug-connected utilization equipment not fastened in place, or both, are also supplied.


What I get from this is that any one piece of equipment that is plugged in cannot be more than 80% of the circuit.
The circuit itself can have a 100% load.

Stan,

Sorry for my sloppy math response. I was wrong on the applicable loads also.

Actually 2011 NEC 424.3(A),(B) is the correct citation and it totally supports both you and milkman's response.

The only thing I was correct on was the 80% continuous load factor.

I do not believe that cite 210.23 is the correct citation because this citation is dealing with "Cord and Plug" equipment, not hard wired. Unless, Milkman has equipment that he has to install 240V receptacles for.

I do not believe that cite 210.23 is the correct citation because this citation is dealing with "Cord and Plug" equipment, not hard wired. Unless, Milkman has equipment that he has to install 240V receptacles for.210.23 is permissible loads. Not just cord and plug.

210.23(A)(1) and (A)(2) deal with cord and plug, equipment fastened in place, and the combination of the two.