Calculating wall heater loads

[crtemp]

I am going to be wiring a house soon and I can't seem to find a straight answer on how many watts I can run on a 240 volt 20 amp circuit. Do I consider a wall heater circuit to be a continous load? Can I load the circuits up to 4800 watts?

Thanks

 

[Dennis Alwon]

I would consider the wall heater at 125%

 

[david luchini]

I agree with Dennis. See 424.3(B)

 

[kbsparky]

A 20 Amp 240 Volt circuit for electric heat has a capacity of 3840 watts (80%).

You have to figure it on a continuous load basis.

 

[crtemp]

Is that the code or just good practice? I thought a continuous load was something that was intended to run for 4 hours or more per day? Is it 4 hours non stop or just 4 hours total?

 

[david luchini]

Is that the code or just good practice? I thought a continuous load was something that was intended to run for 4 hours or more per day? Is it 4 hours non stop or just 4 hours total?

Continuous load is a load where the maximum current is expected to continue for 3 hours or more.

A fixed electric space heater is considered a continuous load, by Code. See 424.3(B).

 

[crtemp]

So basically I can get 3600 watts out of a 20 amp 240 volt circuit?

 

[ActionDave]

So basically I can get 3600 watts out of a 20 amp 240 volt circuit?

Yes, if you are supplying electric heat, or other continuous loads. If the load is non-continuous you can go up to 4800 watts.

 

[George Stolz]

Continuous load is a load where the maximum current is expected to continue for 3 hours or more.

A fixed electric space heater is considered a continuous load, by Code. See 424.3(B).

Yes, if you are supplying electric heat, or other continuous loads. If the load is non-continuous you can go up to 4800 watts.

Per the section David cited the wall heaters are a continuous load whether they run for three hours or not.

 

[ActionDave]

True. Whatever the load is if the code requires it to be treated as a continuous load then continuous it is.

But non-continuous loads, and loads not required to be treated as continuous can use the full rating of the circuit. So it is not true that you can only get 3800 watts out of a 20 amp, 240 volt circuit.

 

[George Stolz]

Oh, I see what you're getting at. Good point.