"Evan Gatehouse" writes:

I've been considering the use of Polyfuses (made by Raychem among others)
instead of circuit breakers in an electric panel on my boat. They are a
lot
cheaper (like $0.50 each) and smaller than a breaker. The specs say "100A
maximum current" for a typical 5-10A fuse. This is the maximum fault
current that can be used to trip such a device.

The typical C series Carling hyd./magnetic circuit breaker has a
interrupting capacity of 7500A @ 80VDC. This is the toggle type circuit
breaker that you see on most new boats.

My question: is 100A interrupting enough? If there is a short in a
typical
wire, will fault currents exceed that?
snip

What you are asking is really, "What is the short circuit available on this
boat?"

The answer is dependant on the size of the house bank.

5,000 amps DC would not be considered unusually large.

BTW, what you are asking is the answer to a coordination study, something
consulting electrical engineers do for a living for large industrial
facilities.

For the device in question, you need to determine the maximum let thru
current under a bolted fault condition.

The manufacturer can provide this info.

HTH


--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
Visit: http://home.earthlink.net/~lewhodgett for Pictures