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From: (no name) (no email)
Date: Sat Sep 06 2003 - 10:45:47 EDT
In a message dated 9/5/2003 1:59:17 AM Eastern Daylight Time,
writes:
> Yes, that is true, but one thing that can be done to help prevent that sort
> of situation is to use main breakers with very heavy cables feeding them,
> then smaller and smaller protection devices on the branch circuits...
Yes, I do that too.
I have run a twisted pair of 1/0 wires from the house batteries amidships
forward along the hull/deck join up both sides of the boat to the windlass, and
another set aft to the transom. These big wires are "protected" by one of the
3 phase, ac circuit breakers I have and all the loads (except the windlass)
branch off these big twisted pairs with in-line fuses.
It has worked very well for me. I can shut off all the DC in the boat (exce
pt for the genset and main engine starter circuits) with just one switch in
case of a magic smoke release or for working on the system, AND the loads, which
are relatively small, all get very high quality juice as if they were
connected directly to a nearby battery.
>>>>Fires here HAVE been reported in several instances over the years, and
because these cables are so big, the heat that builds up in a short is
substantial. It has burned up at least one boat that I know about.
>>>
Yes, I understand that sometime, somewhere, everything possible has happened,
however I have to play the odds. There are so many ways to have problems on
a boat, perfect safety is impossible. I have to spread my resources around
where they will have the best effect.
I have arranged my big wires so that it is very unlikely that there will be
any high current shorts, and in the case of the engine room starting wiring,
there is no combustible material anywhere near the wires. I have considered
some sort of protective fuse or breaker in these lines but I have not come across
such a device for the 800 or so amps normally drawn during main engine start
and imagine it would be quite expensive If it were a fuse I would also have
to buy the fuse holder and at least one spare.
Norm
S/V Bandersnatch
Lying Portland ME
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