On Sun, 30 Oct 2011 01:24:49 -0400, "Michael A. Terrell"
wrote:


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.


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.


Murray was interchangable with a lot of other brands.

American Switch
Arrow-Hart Bryant
Crouse Hinds
Cutler-Hammer
Electri-Center
Frank Adams
General Electric
General Switch
Gould
GTE Sylvania
Montgomery Ward
Murray
Siemens
Westinghouse/Bryant

Sears had a series that fit at one time, as well.


A lot of breakers and panels are shipped with little or no ontact
lubricant, which causes early failures. Some 'electricians' wipe it off
the buss bars, causing their own problems.

http://ecatalog.squared.com/pubs/Cir...0600DB0109.pdf


Ive gotten stab slot burns..badly smoking the base of the breakers and
often breaking the shells of the breakers around the stab slots. The
stabs themselves are eroded and rough with pits and burns.

And the breakers have never tripped..so its not a result of an overload.

The only thing I can think of..is salt air..but its a couple miles
inland from the Pacific and nothing else shows any signs of salt
corrosion.

These breakers are only 20 amp, 3ph and are carrying about 8 amps under
load..with less than 18 amps on startup..everything is running under
VFDs.

And Im ****ed off as I cant figure out why this is happening. And its
only happening with the new Murray panels. Nothing at all with the old
SquareDs and other old weird brands that Ive not swapped out yet.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch