WillR wrote:

Roy Smith wrote:
Leon wrote:

If anything a lower rated circuit breaker is going to make the motor
heat up more when under a strain because it is not getting enough
power.

Enough current???? Have actually seen this -- in a failure mode of a
breaker - ALTAIALFA (a long time ago in a land far away) But it was a
handful of failures in thousands of machines. Highly unlikely -- but
maybe not impossible. I will leave it to the EE's in the group who might
want to debate this. I am sure that someone here can do some
calculations and dig up some data to prove something. I certainly
can't/won't these days.



Ugh. Where do people get this stuff from? A breaker either stays
closed or it opens. If it's closed, the circuit will deliver as much
power as the load can draw (minus resistive losses in the wiring
itself). If it opens, there's no power delivered. There is no middle
ground where the breaker is not delivering "enough power".


And if the breaker fails by developing a higher resistance?

Then how does it make any difference if the breaker is rated for 1 amp or a
billion? If the failure is corrosion of the contacts or something else
that causes increased resistance in the contacts it's going to occur on a
breaker of any capacity.

The contacts are simply metal touching metal. They may be exactly the same
size in breakers with a very wide range of current capacities. What makes
the breaker "break" is a mechanism that opens those contacts, not anything
having to do with their innate properties.

Actually
seen this in a handful of failures out of many thousands of
motor/breaker circuits in a manufacturing situation. I was just glad I
could pass the analysis to someone competent. Again ALTAIALFA -- QA is
probably a lot better and techniques have changed -- so it probably
doesn't happen any more...

So? Having a larger breaker would have made no difference.

I am beginning to wish that we had the Chemists equivalent of STP
(Standard Temperature and Pressure)

Then we could all say that when we mean when we say "normally" -- which
isn't used often enough...

Then we wouldn't debate this stuff unless it was egregious enuff to
really rile us up. I am so MAD!!! Cause I saw some of these failures 30
years ago and -- IT CAN HAPPEN! I SWEAR! TO DENY IT IS WRONG!!!!

There is no question that breakers can fail in various ways. The question
is whether using a larger one would eliminate the kind of malfunction that
you observed, and there is no reason to believe that it would.

And I swore I would never post on one of these threads. But if a cool
head like Robatoy can give at least one shot I will allow myself _once_.


Did I mention I HATE COMPOUND MITER DESIGNS?

I swear by the Red Green payer that I will do this no more. I swear...


OKOK AMT. Breathe deep.



--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)