In a message dated 10/04/2001 6:04:32 PM Eastern Daylight Time,

<< I plan on running two 15amp or 20amp circuits to the obs (one for scope and
computers, the other for lights and misc. Distance from the main breaker
panel back at the house is probably between 350'-500' (haven't measured
exactly yet - depends on whether I run the wiring through the old barn, or
around it). >>

Is the barn by the house, or a significant part of the distance to the
observatory?

I'd consider running a heavier service to a secondary breaker box in the barn
if you might want additional power in the barn for other reasons at a future
date. Then your lower-amperage run from there to the observatory will be
shorter. Part of the cost of getting service to the barn might be offset by
potentially smaller wire required the rest of the way, depending upon exact
distances and loads.

I'd definitely run 220 volt service all the way to the observatory, rather
than just 110 volt. Specifically, run 3-conductor (plus ground) wire rather
than 2-conductor. This gives you your two separate 110v circuits (without
going to a higher wire gauge to carry double the amperage on one 110v
circuit, but you weren't considering doing that) and avoids the waste of
using (2) 2-conductor UF cables instead which would add an unnecessary second
ground wire and second neutral wire. For instance, you can get away more
cheaply with one 10/3 UF cable rather than two 10/2 UF cables, both of which
are probably much better than a single 6/2 or 4/2 cable to carry the same
load, both for cost and design reasons.

I'd also definitely buy a 500 foot spool if a run is over 250 feet, and a
1000 foot spool if over 500 feet, to avoid needing a junction box partway,
unless there's a convenient spot like your barn for it. If you're not using
nearly all of the cable, dream up some use for it while your trench is open,
or ask your electrical supply house about cutting the length you need, plus
some, all in one piece. Or better yet, work a deal to take the whole spool
and later bring back the remainder still tightly up for a partial refund.

--------------
Anecdote:
In 1986 when building a pumping station down the hill from my new house under
construction, I buried 700 feet of 10/2 UF from a 1000 foot spool, to my
property line. Then I temporarily ran two 250 foot coils of 14/2 an
additional 500 feet along the right of way down to the pumping station, to
run a circular saw, etc. in a damp concrete box underground. Yikes, don't
forget the GFI if you do anything stupid like that! The saw started up at
maybe 2/3 the normal acceleration but ran fine, despite the numbers not
looking great on paper. Most of the voltage drop in my case was on the
14-gauge portion of the 1200 foot run I'm sure.

I also used the remainder of the UF cable to run additional lines out to a
convenient spot 100 feet from my house, in my yard by the driveway for
potential car-related uses, an electric chainsaw, landscape lighting,
whatever. It beats digging up and tapping into the single, critical long
cable later.

The 10/2 UF, despite being OK for direct burial, was put in a trench with 4"
PVC pipe set in sand, more sand and scraps of wood and drywall above the pipe
to help keep frost from punching the many rocks into it. Obviously, you need
to check your local soil types, codes, etc.

One hint if you're pulling the cable through pipe: don't connect the pipe
sections togetheruntil you've pulled the cable all the way through with a
little space between pipe sections, to be able to get at it. Leave a bit of
slack in the cable as you go, too. Once it's all in place, start connecting
the pipes together at the opposite end from where you can still add more pipe
over the end of the wire, also paying heed to what will happen if you have
sharp bends in the route along the way where you can't move the pipe around
the bend.
--------------

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