On Sat, 25 Apr 2009 19:23:52 -0700 (PDT), "
wrote:

On Apr 26, 1:51*am, Bruce L. Bergman

* 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.


* * -- Bruce --

When did the change to aluminum buss bars occur? I was not aware they
had done that. Will have to check the panels here.

Dan

Oh heck, that started in the late Fifties, when Copper got more
expensive than AL. They are the norm now for small panels - If the
bars are tin plated, they are most likely Aluminum.

Some large industrial panelboards were designed to use Aluminum main
busses in larger amperages - a lot of Zinsco (Sylvania) switchboard
distribution sections and panelboards still out there that push 400A
through big L-shaped extruded aluminum busbars to Q style breakers.

They usually leave Copper busbars bare, and the patina is the real
symbol of Quality.

-- Bruce --