On Sat, 29 Oct 2011 14:31:59 -0700, Gunner Asch
wrote:

On Wed, 26 Oct 2011 21:52:34 -0700, jk wrote:

"Michael A. Terrell" wrote:



Manufacturing tolerance will decide which breaker goes first....


Sure, with Chinese breakers.

That's why I sugessted adding the external dual pole breaker with
common trip.

You can get the "aircraft style" 2-pole handle-tie lever breakers that
will work fine in that portable generator - replace the two little
pop-button style breakers.

There are Line Lug - Load Lug US Style breakers available that can be
panel-mounted - GE, Square-D and others. But they're huge in
comparison, they won't fit.

With ANYBODY's breakers. Especially cheap thermal magnetic ones.

The tolerance bands are typically +/- 10%.
And that is assuming they work at all.

jk

I should stick in a bit of information here about breakers. One of the
common types readily avaible are Murrey breakers.

They suck badly. Ive had to replace 22 of them this year in an
installation thats only 3 yrs old.

Burned contacts at the base of the breaker, along with breakers that
trip far far too easily.

After this year..Im going with SquareD in all my installs. Murrey was
cheaper..but the amortized costs are more, both in hardware and down
time.

The new Murray MP series aren't that bad, and I deal with them every
day in residences and retail...

But if you're dealing with industrial shops, they really should be
installing Bolt-On Panelboards and breakers, they won't have those
buss problems because it's clamped on with a 10-32 screw. You can get
them Square-D QOB Bolt-On panels if you insist on staying with them.

When given a choice I always stay with a 1" "Industrial Interchange"
style that is interchangeable in an emergency - you can stick a
Cutler/Challenger or GE in a Murray panel in a pinch, or vice versa.

Stay away from Square-D Homeline, they are NOT true I.I. style and you
have to modify the Homeline buss with side-cutters to get a Murray or
GE breaker in, Pool Men do that to me all the time because they have a
Murray breaker with them. But snipping a chunk out of the Aluminum
buss breaks the tin plating and speeds up the "Self-Destruct Tin
Corrosion" feature, and I'll soon be installing a whole new panel.

You can get Square D QO now, but eventually they will be discontinued
in favor of the Homeline and then the fun starts.

GE is good but I won't put them in new, they have proprietary breaker
stabs on their 'skinnys' and there's a cross-bar where a regular
Murray or Challenger 'thick' won't plug in. You have to go get a GE
breaker - but again the Pool Men just start snipping off the side
cross-bars to get a Challenger that they have with them in, see above.

And the Aluminum buss stabs in any brand panel WILL fail after 20 or
30 years if they aren't treated right - like the builders that sprayed
Wallboard Texture into all the open panels in the development, and
then their Electricians doing trim-out just stuffed the breakers on
over the gypsum splatters. Twenty years later, the panels start
burning up...

Put an Aluminum Buss panel anywhere near salt water, and that's more
like 5 to 15 years.

Half of that you can blame on cheap people, even if you can order the
panel with a Copper Buss option most people won't pay extra for one.

You want trouble, the older Challenger Half-size split breakers with
the "hook" buss stabs - they don't have a pressure spring, so they get
stretched real easy and get loose on the buss stab, then start burning
up the stabs.

Same thing with Zinsco breakers, especially the skinny little stabs on
the R38 and RC38 twins.

And don't get me started on FPE Stab-Lok - sending 200 Amps through an
8-32 Screw to the vertical buss, and their miniature stabs that don't
stay stabbed or locked into the busses. And the 2-pole breakers that
fail and get jammed internally and then will not open for anything -
even a roaring fire. FPE is Bad Juju, Replace The Whole Panel at the
first hint of trouble.

-- Bruce --