rchtravel wrote:
Yeah I know, the title is interesting huh? Let me explain...I bought
a 26 year old house and gutted it replacing just about all the wiring
except for some of the ceiling light runs. The original main panel is
100 amp and because of an addition that was built, another 100 amp
sub-panel was installed 18" away and next to the "main" panel. This
was done by a professional electrician with the proper permits pulled
and final inspection was approved about 2 years ago (the state is MI
by-the-way). Oh, and he also replaced and installed new wire from the
transformer on the pole to the original 100 amp house panel.

NOW MY QUESTION:

I have a barn that needs power and requires a wire run of about 75-80
feet (actual run length from box to box, not just the distance from
house to barn). What I would like to do is run direct bury, #2
aluminum (4 wire) from a 100 amp breaker in the house sub-panel,
underground to another 100 amp sub-panel in the barn. The electrician
I hired 2 years ago said that doing so would not be a problem as long
as the 2nd sub panel in the barn was properly grounded. I would like
other opinions or advice on this please.

Why 100 amp instead of 60 amp in the barn you ask? Why not, besides I
already have a Square D 100 amp panel I bought that was much cheaper
than 60 amp panels I looked at, not to mention the expandability 100
amps offers. In the barn I plan to run lights, 20 amp power outlets,
an air compressor (220), small arch welder (220), gas furnace, and
typical power tools such as a table saw, drill press, etc...

Of course, if my "plans" aren't safe, than I would certainly change
whatever was needed to be considered safe. That's why I'm asking for
feedback from this group. In hind-sight, I really wish I would have
bought a new 200 amp panel when I remodeled the house. Ah...if only I
knew everything....lol

Thank you in advance, it's appreciated!

RC

If your service load calculations indicate that your total load,
including the barn, will not exceed 100 amps then you can proceed as you
outlined. You do, however, have some alternatives you might want to
consider.

If you are in the US you can install a large NEMA 3R box at the meter in
which you can tap off a new service lateral to your barn. Those
conductors must remain entirely outside of your house. That lateral
would be three wire and you would wire the barn exactly as you would a
new service.

If the load exceeds the ampacity of the present service you can do a
heavy up by using a new service equipment panel to supply feeders to
both of your existing house panels and the new panel in the barn. Then
you can supply four wire feeders to each of the three panels. This
eliminates the cost of rewiring the existing circuits but you will have
to separate the Equipment Grounding Conductors, if any, from the
neutrals in the panels that are supplied by feeders. It may not be
practical to do that if the panels are of the older type that are only
suitable for use as service equipment.
--
Tom H