new circuit questions-help


Old 11-06-06, 05:45 AM
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new circuit questions-help

i'm adding some new circuits in a 2 story home for a whirlpool and ventilation fan on the second floor. unfortunately, the wiring needs to go outside the home from the attic for about 10 ft to get to the garage where the panel is located. the prior owner has already done this with galvanized pipe.

is it ok to snake my 2 cables thru this pipe or should i make some other route? thanks for your help in advance>>>

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Old 11-06-06, 06:06 AM
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The cable does not HAVE to run outdoors. That may be the easiest route, but the cables do not have to run that way.

Any cable outdoors must be waterproof cable. Make sure what you use is waterproof.

Whether or not you can add anything to this conduit depends on how many cables are already there; whether they are cables or individual wires; the diameter of the conduit, the amount of current being pulled, the length of the pipe.

You almost certainly would be better off finding an alternate path for the cables.
Old 11-06-06, 09:36 AM
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You probably wouldn't be able to add additional cables through the existing conduit for practical reasons (EG, it's hard enough to pull one UF cable through conduit, letalone 3!). But there are also codes that prohibit it. Cable current ratings (15A, 20A, etc) depend upon a certain level of ventilation to be able to dissipate the heat that builds up in the cable. When you start to put a bunch of current-carrying conductors in a single piece of conduit, they can no longer dissipate enough heat at their rated current to stay within their rated temperature, and have to be derated, which is something I'm sure you don't want to deal with.

You can add additional conduit, which is pretty easy to do, or find a way to route it indoors. If you're routing the cable outside (even if it's in conduit), you need to use waterproof cable. The waterproof version of the Romex (NM-B) you're probably used to is UF cable, and it installs in much the same way. It's a little harder to strip, but not much more expensive and can otherwise be used pretty much exactly how you'd use romex. Alternately, you could use THWN (individual wires) through the conduit, and make wirenut splices in the conduit boxes on either end.

If the conduit is in an area where it's not prone to damage, you can use PVC SCH-40 (grey PVC in your big box) which is very easy to install. You can easily pass #12-2 UF through 3/4" PVC.

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