Re: indoor-type electrical power wiring buried under lawn-- how long will it last?

On Sat, 17 Feb 2007 00:33:08 GMT, ehsjr <ehsjr@xxxxxxxxxxxxxxxx>
wrote:

Rob Lucas wrote:
I've just discovered that the previous owner of my house installed a
15 amp circuit feeding the detached garage by burying a standard 14
gauge flexible-metal-conduit cable about 6 inches under the lawn. This
is the stuff that has the two plastic coated conductors and an
unshielded ground wrapped in a continous coil of glavanzied steel (or
is it aluminum?).

Anyway, how many years can I expect before this installation causes me
problems? I figure worst case in 20 or 30 years the shielding and
ground wire will have rotted away, but the first thing the cable does
in the garage is go through a GFI outlet, so realistically it should
still be safe even without the ground. How long before the standard
plastic coating on the hot wire is deteriorated by the soil? (assuming
someone doens't put a garden shovel through it first!)

I really dont want to dig this whole thing and replace it. Cheers.

The GFCI receptacle in the garage does absolutely
nothing to ameliorate the problem. The receptacle
can protect from a problem in a device plugged
into it, or from a problem dowenstream of itself.
It can do nothing to protect from a problem between
itself and the power source.

The only right answer is to replace with new, up to
code wiring, or just disconnect (at the house end)
and abandon or remove the old stuff. Per the US
national code "up to code" with regard to burial
depth, means, in general:
Direct burial UF cable without a raceway must be
buried at least 24" deep. If you use rigid metallic
raceway listed for underground installation, it must be
buried at least 6". If you use non-metalic raceway
you have to go 18". You can reduce that to 12" if
you GFCI protect the circuit, and if the circuit is
no more than 20 amps.

There are specific locations (for example under
driveways) with different rules, per 300.5 in the
National ELectrical Code

Ed

Very crappy


Andy
.

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