On 2011-10-03, David Lesher wrote:
" writes:


My friend had a 440 motor or line short right in front of him in an
elevator motor room. He was temporarily blinded for a couple days. He
said it felt like someone poured sand in his eyes.

OSHA has gotten religion on the arc flash issue. The #1 chance
for such that will kill folks is when you close a large
main/sub-main breaker. They can and do explode outward with
enough force to blow apart cabinets, taking out the chump
standing there closing the breaker.

So, why exactly do they explode? Can you explain?

There's now many types of motor/hydraulic powered breaker
closers. They attach with magnets, the arm is on the
handle. You stand 20 ft away behind Lexan etc and push
the button.

There's also required "arc-flash clothing" -- I think the point
being it won't catch fire and melt onto the skin, but I'm not
sure on this.

In residences, the NEC has spec'ed arc sensing breakers for
bedrooms/living rooms, I think. These can be a PITA as
brush-type motors [Skilsaw, etc] can trip them.