You should get one of those "subset of the National
Electrical Code relevant to homes" books, either
from the library or HD, etc.
Here is the one I have: ISBN 087765457-3
Browse through the Lowes or HD book area for other
relevant-looking titles.
What you are planning is not particularly exotic.
Strictly speaking, you have some flexibility in the
size of the wire used to feed it. The more
relevant breaker is the one back at the main panel
that feeds the line to the box. The line must have a
capacity at least as large as that breaker. You also
need to be sure your main box can supply the desired
current.
By the time you buy the conduit and wire, rent a
trencher, etc. etc., the price of that box may not be
such a big deal. Also look at the temporary boxes
they install at building sites to supply power to the
builders.
Probably you can use heavier plastic conduit, at least
18" deep. The books will all discuss that issue.
One other thing: The wire gauge is determined by both
the desired current capacity, and the maximum
allowable voltage drop caused by the length of the
wire. In other words, long runs have to be done with
heavier wire than short runs. The books will have
formulas for this.
On my previous house, I did a nice rewiring job on the
detached garage, running a new buried conduit, adding
a sub-panel, lots of outlets, etc. I did everything
by the book, getting permits and inspections, and it
was quite a satisfying project.
Doug
--- Mark Andy <mark@sccaprepared.com> wrote:
> Howdy,
>
> I'm once again considering what I'd need to do to
> get an easier power
> access for my RV and trailer.
>
> I'm thinking of getting a box like this:
>
>
http://www.pplmotorhomes.com/parts/rv-power-cords/rv-electrical-outlets-new.htm
>
> and mounting it on a 4x4 pressure treated post at
> the corner of the
> driveway. To get power to it, I can poke a hole out
> of the garage above
> the ceiling, then into conduit down into the ground,
> then in the ground to
> the corner of the driveway at the base of the pole,
> then in conduit up the
> pole and into the box.
>
> First... Does that sound like it would meet typical
> code & "not dumb"
> requirements?
>
> Second... Total wire distance is probably on the
> order of 150' or so from
> the electrical box. Since there are two breakers in
> there at 30A and 20A,
> I assume I need to be able to handle 50A on the line
> I run, correct? What
> wire guage do I need for that?
>
> For the in-ground part... What depth? I'm in Ohio
> and the ground does
> freeze. I'll also want to be able to drive typical
> compact (not lawn)
> tractors over the lawn where its buried, etc. In
> conduit for the in
> ground part as well? Plastic or metal?
>
> How fast is a typical rental trencher for this type
> of stuff? The ground
> here isn't particularly rocky or anything.
>
> Finally... $130 seems like an awful lot for a metal
> box with a couple
> breakers & receptacles... Are there any cheaper
> options? I want it to be
> rain-proof with the cables plugged in, but I don't
> care about having
> breakers at the box. I need a 30A receptacle for
> the motorhome and the
> trailer can get by with just regular 15A or 20A.
>
> Appreciate any advice...
>
> Mark
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