Infrared Heater circuit sizing

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Cow

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I'm planning on a couple of 40 amp(480 3 phase) branch circuits for six (480 1 phase) heaters, the heaters themselves only draw about 15 amps. Is there anything that allows you to downsize the whip to the heater? Or do I need to run #8's all the way?

I've been through Art. 424 and haven't seen anything allowing it. I wasn't planning on using any supplemental OCP at the heaters themselves.

Thanks.
 
Cow said:
I'm planning on a couple of 40 amp(480 3 phase) branch circuits for six (480 1 phase) heaters, the heaters themselves only draw about 15 amps. Is there anything that allows you to downsize the whip to the heater? Or do I need to run #8's all the way?

I've been through Art. 424 and haven't seen anything allowing it. I wasn't planning on using any supplemental OCP at the heaters themselves.

Thanks.
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If your OCPD is rated for 40A protection, then your wire needs to carry that. But you know that. No I know of nothing that allows you to downsize the whips. As a thought, why are you running 40amps and, therefore, using eights? With Dennis, I'm wondering why you don't just run a 20A circuit to each. But maybe it has to do with design or distance, or whatever....
 
Sorry guys, didn't mean to confuse you.

I'm using a Fostoria factory made contactor panel capable of two 50 amp 3 phase circuits. I have six single phase heaters to wire into these two 3 phase circuits. So, 3 heaters per circuit at 15 amps(single phase) apiece.

I wasn't sure if you could downsize whips since it's allowed for light fixtures and this wasn't feeding a receptacle, but a known load.

http://www.google.com/products/cata...a=X&ei=FADoTuzfN8OyiQKVrIWjBw&ved=0CE8Q8gIwAA

The customer purchased all of this, I just have to install it.
 
Does the heaters draw 15 amps or is that what size circuit needed for individual install.

If actual rating were just a little lower only a 30 amp circuit would be required to run 3 balanced across phases.

I have done exactly what you are describing less the fostoria controller before, but heaters were only like 1500 or 2000 watts and it worked with a 20 amp circuit.

Next question for your installation is whether or not heaters can be on a 35 or 40 amp circuit, you may need overcurrent protection at each heater either way.
 
zog said:
Let me know how those IR heaters work, I have been considering buying a bunch of those.
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Sure.

kwired said:
Does the heaters draw 15 amps or is that what size circuit needed for individual install.

If actual rating were just a little lower only a 30 amp circuit would be required to run 3 balanced across phases.

I have done exactly what you are describing less the fostoria controller before, but heaters were only like 1500 or 2000 watts and it worked with a 20 amp circuit.

Next question for your installation is whether or not heaters can be on a 35 or 40 amp circuit, you may need overcurrent protection at each heater either way.
Click to expand...

They are a 2 lamp 480V 7.3kW heater. About 15.2 amps apiece. I figured 15.2 amps x 2 heaters/phase x 125%=38 amps=40 amp fuses.
 
Cow said:
Sure.



They are a 2 lamp 480V 7.3kW heater. About 15.2 amps apiece. I figured 15.2 amps x 2 heaters/phase x 125%=38 amps=40 amp fuses.
Click to expand...

If you balance them across phases and have 3 units you have 1.73 heaters per phase. 15.2 x 1.73 x 125% = just shy of 33 amps.
 
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