On Thu, 23 Apr 2009 06:27:02 -0500, Terry
wrote:

I have a 220v 30a double breaker in its own outdoor box (Gould WEQ2
ITE, whatever that means), about 35 yr old, that is connected only to
an upstairs window AC and an outdoor outlet. Since the shop is very
close to the house, I've never properly wired the shop. I just plug a
homebuilt extension cord into the outdoor outlet to run my lathe,
drill press, etc. (Lathe is the only tool that draws 220; I have a DC
motor with regulator that runs up to 180 V on it.)

Gould and ITE were bought out by Siemens. If you want the easiest
replacement where the dimensions and physical layout of the knockouts
match, get a Murray or Siemens sub-panel.

Anyway, one side of the breaker where it pushes into a (aluminum)
terminal in the box apparently corroded to some extent, then shorted
out. I don't know when it happened but was thinking some sort of
power surge during the Feb ice storm in this neck of the woods, which
knocked out power to the county for five days and ours for almost two
weeks.

Wondering (a) why only one side would short that way; (b) is aluminum
suitable for those terminals, or is that old technology, away from
which I should run; (c) where I could get a new terminal (10 minute
job) instead of replacing the whole box (electricity off for several
hours).

A) The aluminum buss in the breaker panel went bad, and that killed
the breaker stab where it plugs in.

B) It's newer technology, driven by price to the end user - you
can't let the competition sell their breaker panel for a buck less,
they'll take all your sales. The 'builder model' panels have tin-
plated aluminum busses to save a buck over using copper busses, and
for the average use in a nice dry location they work just fine for 30
to 50 years - that is, till the tin plating wears through from breaker
changes or is otherwise broken, thin plating on an edge with a burr
can do it.

The aluminum oxide 'corrosion' eats it's way under the tin plate and
the connection goes bad - aluminum oxide is an insulator...

C) You aren't going to get a new terminal - the catalog and the
label on the door says they sell replacement interiors for panels. But
the reality is you can special order it, wait weeks for them to make
and ship it, and pay double the cost of a new panel.

If your old steel can isn't rusted and they still make that brand of
breaker (not an orphan like Zinsco or Federal Pacific) and that model
of panel (or something close) you can buy one and do a "Gut Swap" -
mount the new interior in your old can, and save the trouble of
physically swapping the steel box...

But the legalities of a Gut Swap are a bit murky, so it's not the
first choice - and NOT for the DIY-er!! You usually have to modify
pieces and drill new mounting holes, and it has to be thought through
from both the mechanical and electrical angles, insulation sysrtems, .
Otherwise the whole thing shorts out when you reenergize it, and there
is going to be some 'splainin' to do.

(This is normally used on large interior panels flush-mounted in the
wall with a dozen or more conduits leaving, where it would be a two or
three day gold-plated ******* of a job to swap the steel can - and the
residents can't be off for three days, so you have to rig up temporary
power. And then you have to repair the big hole in the wall you made
for access, and prime and paint...)

They DO sell new breaker panels with copper busses, but unless you
work with a coastal wholesale house that gets a lot of call for them
you usually have to special order them. If you are anywhere near the
ocean (or working on a boat power system), they are a necessity, the
salt air tears up exposed aluminum with a vengeance.

(The Boss had a big go-round with a customer on the cost when I
insisted on a copper buss panel - a rental house where the owner
didn't want to spend a dime more than necessary, but I didn't want to
go do it again in 5 years because "You did a crappy job!!" The house
is built on wood pilings over the beach,10' above mean high tide line,
the old panel was physically fine except for the corrosion.)

If this sub-panel breaker box was scabbed on to your existing main
panel (using the "10 Foot Tap Rule") because it is out of spaces,
sounds more like you need to change out the Main Panel. Changing this
sub-panel might be putting a band-aid on a limb amputation.

What does the rest of the electrical system consist of, and how big
is the house? (Define the REAL problem...)

Changing out the Main can be a huge job if you have to upgrade from
a 30A 4-circuit plug fuse fusebox from the 1930's or 70A "Crowfoot"
six-breaker panel from the 1950's to a modern 200A 40-breaker panel,
and then rooting out the bad wire in the house (anything before the
1950's is probably Rubber insulation, and suspect) to something
approaching current standards - but it's still a Whole Lot Cheaper
than rebuilding the house after the fire. Trust me on this.

-- Bruce --