junction box


Old 08-12-07, 07:05 PM
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Join Date: Aug 2007
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junction box

I was checking to see if it would be a good ideal to run 6/3 inside wire from main 100 amp breaker box using a 60 amp breaker to a junction box then use
6/3 outside wire to run to my garage subpanel from junction box. I will have to run 70 feet of indoor and about 30 feet outdoor. Is this safe and what kind
of juction box will I use?

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Old 08-12-07, 08:03 PM
Join Date: Sep 2003
Location: Central New York State
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I would use UF cable the entire run. Why add a potential failure point?

If you do go the route of a junction box, it must remain permanently accessible with a blank cover over it. I would use a large box.

Last edited by racraft; 08-13-07 at 07:03 AM.
Old 08-13-07, 06:34 AM
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Each 6 ga. conductor is calculated at 5 cubic inches. Two cables containing 3 conductor = 6 + 1 ground = 7. 7*5 =35.

You will need a box that contains at least 35 cubic inches. A standard metal 4x4 1 1/2" deep box is only 10.3 cubic inches, a 2 1/8" deep metal 4x4 is only 14.5 inches.

Plastic boxes will have their capacity stamped in the back of the box.
Old 08-13-07, 07:07 AM
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I'd agree with racraft. The additional cost of the UF is minimal, and it would probably be more expensive to buy a large enough box to hold the splice. Plus, splicing 6ga is more of a pain than just wirenuts. Not that it's that hard... but why do it if you don't have to.
Old 08-13-07, 05:59 PM
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I'm going to run 6-3 indoors all the way and put the 20feet outside in water tight conduit. I was told this would be fine as long as I run conduit all the way. And the cost between inside and uf is about 1.50 a foot. ($150 more) Conduit will run me $20.

Thanks moose
Old 08-13-07, 07:51 PM
Join Date: Sep 2003
Location: Central New York State
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Do not use NM cable outdoors, even in conduit. The conduit will fill with water and the cable will fail. Whoever told you it would be okay is incorrect.
Old 08-14-07, 08:13 AM
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Even if water doesn't infiltrate, air will. And water will condense out of the air that gets in.

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