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

[Rob Lucas]

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.

 

[Donald]

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.

Don't let the city inspector find this, you'll be digging it up with a
fine to boot.

Underground AC cables need to be rubber coated, PVC does not count.

So, choose you poison.

donald

 

[John Popelish]

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.

I don't think the spiral armored cable is rated for direct
ground contact. Not only will the galvanized steel shield
rust off, giving you an unsafe ground path back to the
panel, the wire insulation is not rated for the moisture of
direct burial, and will eventually (if it hasn't already)
develop current leaks that will spin your meter.

I think I would replace it with type 12-3-UF with ground
(rated for direct burial). This would allow a current
rating of 20 amps, but lower voltage loss for a 15 amp
circuit, but also would allow expansion to a full 240 volt
circuit, if you ever decide to put something larger, like a
compressor, in the garage. The cost of the wire is trivial
compared to the cost of the slot to lay it in.

 

[Homer J Simpson]

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

I cannot believe this complies with your city codes.

 

[Rob Lucas]

I cannot believe this complies with your city codes.

Oh, I'm 100% sure it doesn't. But what I'm trying to do is satisfy my
curiosity about why a PVC coated wire would ever develop a current
leak just because its in contact with moist soil.

Obviously, if/when I go to sell my house I would have to replace this,
or fully disclose it. Unfortunately for me, I bought this house in an
estate sale, so there was no living owner to provide me with any
disclosures. live and learn...

 

[Homer J Simpson]

Oh, I'm 100% sure it doesn't. But what I'm trying to do is satisfy my
curiosity about why a PVC coated wire would ever develop a current
leak just because its in contact with moist soil.

It won't. But BX isn't designed to be run without the sheath and that won't
survive.

We used to either run plastic conduit or we ran Romex 2 feet deep in sand
and covered it with cement planks (approved where I was).

The proper way over here is to use UF and install it according to code.


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[Michael A. Terrell]

Oh, I'm 100% sure it doesn't. But what I'm trying to do is satisfy my
curiosity about why a PVC coated wire would ever develop a current
leak just because its in contact with moist soil.

Obviously, if/when I go to sell my house I would have to replace this,
or fully disclose it. Unfortunately for me, I bought this house in an
estate sale, so there was no living owner to provide me with any
disclosures. live and learn...

Replace it with schedule 80 gray PVC electrical conduit at the depth
required by your local building inspector. That mess you have now could
develop leakage to the soil, and have a high voltage gradient that could
kill someone.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Andrew Edge]

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.

Don't worry too much you can place cables in water and still
comply with the code! A different story though.

The metal protection is good as it gives mechanical protection and
should satisfy your local regulations. I assume the metal shielding is
around the 2 plastic wires.

In case you don't have metal protection around the plastic.
You need a metal slab or plate on top of the wires or a curved metal
tile.

The Plastic should be at least PVC R2 or a higher rating.
If it is Rubber at least G7 rubber. (Older ones mostly had G5 rubber
I noticed).

6 inches under the lawn is wrong. Should be at least 2.5-3 feet for
wires with metal shielding otherwise >=9feet.

An unshielded ground wire is pretty normal and agrees totally with the
code.

Andy

 

[Fred Bloggs]

Oh, I'm 100% sure it doesn't. But what I'm trying to do is satisfy my
curiosity about why a PVC coated wire would ever develop a current
leak just because its in contact with moist soil.

It depends on soil conditions and the PH, it could dissolve the
insulation within a year or so, and once the integrity of the insulation
is breached, the conductor will corrode at an accelerated rate. The 6"
depth is okay for low voltage but universally out of spec for line
voltage which is usually 18". If all you have in the garage is lighting
then a quick fix would be to convert to low-voltage and replace the BX
with a direct burial UF type of bundle which can *possibly* be pulled
through the existing conduit.

 

[mpm]

Obviously, there's the correct way to do this, and then the way it was
actually done.

If you're not going to correct this now, and you don't intend to
disable the circuit, perhaps you could at least install a GFCI breaker
on this branch circuit....?

-mpm

 

[Rob Lucas]

Obviously, there's the correct way to do this, and then the way it was
actually done.

If you're not going to correct this now, and you don't intend to
disable the circuit, perhaps you could at least install a GFCI breaker
on this branch circuit....?

-mpm

Thats probably the best idea. If/when the insulation is ever breached,
the GFI will kick out before someone gets hurt, and the problem won't
go undetected spinning my electric meter

 

[Rich Grise]

Thats probably the best idea. If/when the insulation is ever breached, the
GFI will kick out before someone gets hurt, and the problem won't go
undetected spinning my electric meter

Of course, you know to put it at the entrance panel end, not the garage
end, right?

Cheers!
Rich

 

[ehsjr]

Don't worry too much you can place cables in water and still
comply with the code! A different story though.

The metal protection is good as it gives mechanical protection and
should satisfy your local regulations. I assume the metal shielding is
around the 2 plastic wires.

In case you don't have metal protection around the plastic.
You need a metal slab or plate on top of the wires or a curved metal
tile.

The Plastic should be at least PVC R2 or a higher rating.
If it is Rubber at least G7 rubber. (Older ones mostly had G5 rubber
I noticed).

6 inches under the lawn is wrong. Should be at least 2.5-3 feet for
wires with metal shielding otherwise >=9feet.

An unshielded ground wire is pretty normal and agrees totally with the
code.

Andy

Total rubbish.

 

[ehsjr]

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

 

[Jim Thompson]

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

At last, someone got out the code book.

I was going to do it myself, but I've been trying to digest a
nasty-worded contract this afternoon.

So I sent it to my son-in-law ;-)

...Jim Thompson

 

[Michael A. Terrell]

At last, someone got out the code book.

I was going to do it myself, but I've been trying to digest a
nasty-worded contract this afternoon.

So I sent it to my son-in-law ;-)

There are still local codes to worry about. Some soil conditions
make the use of metalic conduit in violation of the code because the
soil PH.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Andrew Edge]

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

 

[Klaus M.]

Very crappy


Andy

Hey hey.

Your answer Mr. Edge complies with the Central European directives
which may seem crappy compared to the ones given by Mr. Eddy.

Klaus