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# question regarding voltage loss calculator

#1
01-07-07, 01:17 PM
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Join Date: Oct 2004
Location: USA
Posts: 33
question regarding voltage loss calculator

What is the largest double pole breaker I can use on 10 gauge bx with a 1/2 circuit length of 38ft? I want to reuse my old hot water heater line for a sub panel to feed my basement, which I am finishing. I found a calculator online but i was confused as to whether to specify 240 or 120 for voltage. Currently it's hooked up to a 30amp dbl pole breaker. Is that already the max?
thks

#2
01-07-07, 01:20 PM
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Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
You are doing this backwards. First calculate the load, then the wire and breaker.

no. 10 is limited to 30 amps max regardless of other factors. the load calculator may limit it even further for other reasons.

#3
01-07-07, 06:10 PM
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Join Date: Oct 2004
Location: USA
Posts: 33
I wanted to know what kind of load I am limited to cause i don't want to run a new wire.
thks

#4
01-07-07, 08:49 PM
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Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
If the water heater was wired as a typical water heater then you will need to run new wire. A water heater is a straight 240 volt load, and their is no neutral. A 240 volt sub panel needs a neutral.

#5
01-08-07, 05:01 AM
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Join Date: Oct 2004
Location: USA
Posts: 33
It's a 4 wire circuit. The old heater had 2 elements, one of which was hooked up to a separate meter - I think it only ran at night. So I have 4 wires to work with. Can the neutral be another color other than white if I mark it?

#6
01-08-07, 05:04 AM
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Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
No. The neutral must be white.

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