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# breaker size, wire guage, circuit spec

#1
12-26-04, 07:58 PM
BloodSweatTears
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breaker size, wire guage, circuit spec

Hi,

I am wondering if theer is a FAQ aroudn to explain how to pick a breaker size and wire gauge, as well as design a circuit for 2 220V heaters for my basement.

One is 2kW and the other is 1.5kW. Can I put them on the same wire and breaker (the easiest for me)?

What is the guideline or equation for figuring the number of amps that a breaker should be rated for. The ding-ding working at Home Depot must've had a rough Christmas because he didn't seem to know!

Any help appreciated, but explanation preferred. Thanks....

B

#2
12-26-04, 08:16 PM
BloodSweatTears
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Hello out there guys, I know you are here...

B

#3
12-26-04, 09:45 PM
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BST - Welcome to the DIY Forums.

I am a Chemical Engineer, not an Electrical Engineer, but here is my take:

If my memory serves me correctly, Volts X Amps = Watts

So, Amps = Watts/Volts or for your case, 2000 Watts/220 Volts = 9.09 Amps

and, 1500 Watts/220 Volts = 6.82 Amps

So, it would appear a 20 Amp Breaker should do it. And that should mean 12 gauge copper wire.

I am not an expert in this field, just offering my take on this.

#4
12-26-04, 10:07 PM
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The manufacturer of the heating equipment should provide installation instructions, and you should (must) follow their advice.

If the manufacturer provides no guidance, arkayassoc's analysis is correct.

#5
12-27-04, 06:51 AM
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Join Date: May 2001
Location: Dry Side of Washington State
Posts: 685
Originally Posted by arkayassoc
I am a Chemical Engineer, not an Electrical Engineer, but here is my take:

If my memory serves me correctly, Volts X Amps = Watts

So, Amps = Watts/Volts or for your case, 2000 Watts/220 Volts = 9.09 Amps

and, 1500 Watts/220 Volts = 6.82 Amps

So, it would appear a 20 Amp Breaker should do it. And that should mean 12 gauge copper wire.
3500 Watts/240 Volts = 15 Amps X 1.25% = 18 amps (this is the formula for the U.S. NEC).

#6
12-27-04, 09:43 AM
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Join Date: Sep 2000
Location: Fayetteville, NY, USA
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The logic behind Thinman's reply: NEC doesn't want you to connect more than 80% of the rating of a circuit's wire or breaker. Multiplying connected amps x 1.25 keeps you at 80%.

Juice