Fuses vs. Breakers (was QO Breakers and Panels)[RE-wrenches]

[Travis Creswell, Ozark Solar]

I'm  not the best qualified person on the list to discuss this but I wanted
to get this out so perhaps the less experienced Wrenches could get
introduced to this.  Then perhaps some else could elaborate on my following
generalization.

A very general statement is...

Fuses are for stopping faults before they do a lot of damage and breakers
are for over current protection.  Faults and over current are very different
things.  A fault on a system with more the just a few golf cart batteries
will have catastrophic results. 


Last year I attended a 4 day electrical course given by the local utility
company.  A rep. from Cooper/Bussman and Square D each had about 1/2 day
each to present to us.  The Copper/Bussman rep. had some really, really neat
videos.  He showed what happens to a breaker when it gets hit by a large
(20,000 amp or better) fault.  It exploded and took out the bulk of the
enclosure with it!  It looked like a grenade went off.  There was 4/0 THHN
wired to the breaker and it whipped around like #14 SO cord in the wind.  It
would have killed the unlucky fellow who caused the fault.  Kinda makes you
think about being plumber after watching the video.  Then they put the fuse
to the same test, it stopped the fault with no fanfare.  I bet we could get
these guys to do a presentation at the next MREF.  Cooper/Bussman is out of
St. Louis.  It is a very informative session designed for the installing
electrician type.  It had a little marketing fluff but not much.

So what is the implication?  It is a very good idea to have a fuse in
between the batteries and the breaker.

Travis Creswell
Ozark Solar

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