Cable Inside Conduit - Allowed or Not??


Old 01-02-07, 08:28 PM
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Cable Inside Conduit - Allowed or Not??

I was under the impression that cable (ala "romex") was not allowed inside PVC conduit that runs outside a building. However, the following link describes "romex" type cable #12-2) as appropriate for wet conditions.

Does this mean I can use the product inside PVC conduit exposed and external to the building?
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Old 01-02-07, 08:38 PM
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I believe you can only use romex in PVC on bends only. If you run romex in pvc the entire length, it may get to hot. That is why they tell you to use THWN cable in conduit.

You can run romex without conduit (except on bends).
Old 01-02-07, 09:50 PM
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Article 334 of the NEC covers NM type cable. There is no prohibition to using NM cable in conduit. However, the sheathing makes pulling it through the conduit extremely difficult, and it is possible that the sheathing may become damaged during the pulling process.

The cable you are referring to at the link you provided is actually type UF (underground feeder), which is designed for outside applications. Article 340 of the NEC covers type UF cable. You should not use NM outside even if it is in conduit.

Provided the conduit is rated for outside, above ground exposure, then you may pull UF through it.

However, hotinOKC has a valid point about heat. Conductors are rated for certain temperature ranges, and conduit can prevent heat dissipation. I would take his advice and pull individual THWN insulated wires instead. It will be easier, and will mitigate the heat issue.

Best wishes!
Old 01-03-07, 04:46 AM
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There is no prohibition against cable inside conduit. Period. None. It's harder to pull and takes more space, but it is allowed.

The link posted is for UF cable. UF (Underground Feeder) cable is rated for wet locations. Any outside area, inside conduit or not, must have waterproof cable or waterproof wires.
Old 01-03-07, 07:29 AM
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There are a few terms that need to be nailed down better. "Romex" is a brand name -- they make many different sizes and types of cable, although the most famous Romex is the type NM (Non-Metallic Cable). Type NM cable, regardless of brand name is not allowed in wet locations.

Your link points to a type UF (Underground Feeder) cable which might be manufactured under the Romex brand. Type UF cable is allowed to be buried or installed in conduit in wet locations.

If you look closely at the picture, the UF cable jacket is a heavier waterproof plastic that is moulded tightly around the inside conductors. If you look closely at an NM cable, the jacket will not fit snugly around the conductors and there will be a kraft paper sleeve around the conductors and the bare ground. Jacket color isn't regulated by code, but UF is usually grey and NM is usually either white, yellow, orange or black depending on the conductor AWG.
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