Date: Thu, 10 Mar 2005 07:37:13 -0800

Author: Jason Alferness

Subject: Re: Fuses vs. Circuit Breakers

Post:

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At 03:11 PM 3/9/2005, you wrote:
>Hello Stan and Matt,
>
>Stan...
> >"Even if the breaker could also serve as a switch"
>A circuit breaker SHOULD NOT be used as a switch (although many people
>do...much
>to their liability). The contacts of a circuit breaker are designed to
>withstand the electrical arc during short circuit conditions (and tested for
>tens of thousands of operations) while the contacts of a switch are designed
>precisely to endure millions of operation (at rated current). The
>metalurgical
>process requirements are very different.


I can certainly see that there probably is a significant metallurgical
requirement... though I'm ignorant of the details. And I certainly
wouldn't be one to normally use a breaker as a switch, per se (especially
when there's load...)

But I'm curious about your comment "much to their liability"... I'd never
thought about using a breaker as a switch as a safety issue per-se... (bad
practice maybe, but hadn't given it too much thought honestly)

Is that what your implying? And if so, how? Is there a potential hazard
from arcing? Or mostly a problem from potential damage to the breaker?

I've thrown breakers on many occasions to do electrical work safely, but I
do try to kill the load first... just curious if there's an aspect I may
not have considered.

Thanks for your insight!




-------------------------------------------------------------------------------------------

"A person, who is nice to you, but rude to the waiter/waitress, is not a
nice person. (This is very important. Pay attention. It never fails.) "

Dave Barry from "FIFTEEN THINGS THAT IT TOOK ME OVER 50 YEARS TO LEARN "


Jason Alferness
University of Washington
Room B256B, Physics & Astronomy Building
Campus Box 351560
Seattle, Washington. 98195-1560

Phone: (206) 221-2974
FAX : (206) 685-0635
email: alf@phys.washington.edu

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At 03:11 PM 3/9/2005, you wrote:

Hello Stan and Matt,


Stan...

>"Even if the breaker could also serve as a switch"

A circuit breaker SHOULD NOT be used as a switch (although many people
do...much

to their liability).  The contacts of a circuit breaker are designed
to

withstand the electrical arc during short circuit conditions (and tested
for

tens of thousands of operations) while the contacts of a switch are
designed

precisely to endure millions of operation (at rated current).  The
metalurgical

process requirements are very different.