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Anyone w/experience with URD cable?
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| slc_rookie@yahoo.com 2005-07-01, 6:25 pm |
| I'm running 240V/100A service from my house meter to a detached
garage/shop. Feeder line to be buried (in conduit) and run is 80'
long. Electrical supply house sold me 2/2/4 Aluminum URD (Underground
Residential Distribution) cable. The 4AWG is supposedly the neutral
line-- I questioned why it was 4 and not 2, they're only answer was
that it was all they stocked (though I found 2/2/2 at other supply
houses). Theoretically, if I developed a (obviously unlikely) load
imbalance of 90A or so, wouldn't that fry the neutral and thus negate
my 100A rating?
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| Thomas Horne 2006-01-13, 3:21 pm |
| slc_rookie@yahoo.com wrote:
> I'm running 240V/100A service from my house meter to a detached
> garage/shop. Feeder line to be buried (in conduit) and run is 80'
> long. Electrical supply house sold me 2/2/4 Aluminum URD (Underground
> Residential Distribution) cable. The 4AWG is supposedly the neutral
> line-- I questioned why it was 4 and not 2, they're only answer was
> that it was all they stocked (though I found 2/2/2 at other supply
> houses). Theoretically, if I developed a (obviously unlikely) load
> imbalance of 90A or so, wouldn't that fry the neutral and thus negate
> my 100A rating?
>
You always deduct from the load any 240 volt loads before sizing the
neutral. If your feeder does not supply any 240 volt loads then your
neutral is undersized.
--
Tom Horne
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"Thomas Horne" <hornetd@mindspring.com> wrote in message
news:8OSxf.7661$%W1.3188@newsread2.news.atl.earthlink.net...
> slc_rookie@yahoo.com wrote:
>
> You always deduct from the load any 240 volt loads before sizing the
> neutral. If your feeder does not supply any 240 volt loads then your
> neutral is undersized.
> --
> Tom Horne
The reduction of the neutral is common practice saves a buck or two.
I sure hope the cable you bought has a ground wire with it. You need 4
wires to make it work safely.
Driving a ground rod out a the shop is a unsafe. Your using the earth as a
return path for a fault. Bad things can happen when you do that.
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| Thomas Horne 2006-01-14, 10:21 pm |
| SQLit wrote:
> "Thomas Horne" <hornetd@mindspring.com> wrote in message
> news:8OSxf.7661$%W1.3188@newsread2.news.atl.earthlink.net...
>
> The reduction of the neutral is common practice saves a buck or two.
> I sure hope the cable you bought has a ground wire with it. You need 4
> wires to make it work safely.
> Driving a ground rod out a the shop is a unsafe. Your using the earth as a
> return path for a fault. Bad things can happen when you do that.
>
At the risk of being accused of nit picking I must point out that a
three wire feeder uses the neutral for the fault clearing path. That is
why the neutral of a three wire feeder is bonded to the building
disconnecting means as well as to a grounding electrode system at each
building served. Since the Equipment Grounding Conductors of each
buildings wiring system are also bonded to the building disconnecting
means the only thing wrong with that arrangement is that the neutral is
the only fault clearing pathway just as it is between the utilities
transformer and all service supplied buildings.
--
Tom Horne
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