Cables for Underground Service


Old 11-14-16, 01:29 PM
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Cables for Underground Service

A recent project required making a junction with an existing 120V 12-2G underground cable (going to a yard light) and running new 120V cable 22' underground to install a new GFCI receptacle. So I bought 12-2G for underground service. Person in electrical dept at big box store told me underground cable is gray. When I dug up the existing cable, it was white. The existing cable was there when I bought the house in 2006, the previous owner had been there 40+ years so I imagine the existing cable was installed some time during the 60s or 70s (but don't know for sure). It's buried only maybe 6 to 8 inches. When I skinned the wires of the existing cable to make the connections they weren't bright like new but I guess that would be expected. Both old and new wire are copper. The existing wire exits the crawl space thru a vent, then runs about 35 ft (underground) to the light. So I'm trying to learn:

what dangers there are with having this white wire running 35 feet underground to the light and

if the situation requires replacing the old cable. Thanks
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Old 11-14-16, 01:36 PM
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Can go bad. Main thing is it's not code compliant to run NM underground. The cable needs to be type UF. Also being only buried +-6 to 8 inches is not code, it needs to GFCI protected at the source before going underground and it needs to be buried 12 inches.
Old 11-14-16, 02:14 PM
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If any part of the wiring (where it comes out of the vent to the ground) is exposed and subject to damage that also does not meet code.
Old 11-14-16, 02:30 PM
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It has only been in the last fifteen or twenty years that the color of the outer jacket of cable has had any particular meaning. I have worked with type UF cable that had a white jacket albeit some forty or more years ago.

The ONE distinguishing characteristic that separates type UF cable from type NM is the use of paper fillers. Type NM has the paper and cannot be used in any wet location, including underground. Type UF has no paper, the filler is solid plastic.

So, if the preexisting "underground cable" had no paper fillers under the outer jacket, indeed, the individual insulated conductors were molded into the outer jacket, it WAS/IS type UF regardless of the color of the outer jacket.
Old 11-14-16, 06:35 PM
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Furd, I couldn't have said it better.

But, the fact remains that it wasn't installed properly if it is only 6 to 8 inches deep and was just run through a vent.
Old 11-15-16, 05:23 AM
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Thanks all. I'd wondered about at what point in time cables became color coded, thinking it may have been after this cable was install. There's definitely no paper filler in mine and I understand about what you're saying about the other issues. Your input much appreciated, I'll take it from here. Thanks again.
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