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From: (no name) (no email)
Date: Sat May 05 2001 - 11:06:15 EDT
Subj: Re: lv-ab: Keeping Your Cool
Date: 04/22/2001 3:38:59 PM Eastern Daylight Time
From: Bandership
To: Bandership
In a message dated 04/21/2001 10:40:40 PM Eastern Daylight Time,
writes:
> True, but if it shorts in the connector the dock breaker will trip.
>
>
Sometimes.
The May/June issue of Living Aboard has an article, "Keeping your Cool",
wherein is described the destruction of two shore power cables and a "y"
adapter that were not saved by the dock breaker.
But basically, I do agree with everything in your message.
Breakers and fuses will protect against normal shorts and overloads, but they
will not protect against hot spots created by high resistance connections in
an otherwise normal circuit. This seems to be a major source of fires ashore
and the cause of shore power cable fires at marinas. A hot spot created by a
poor connection can generate enough heat to create a fire without exceeding
the trip current of the breaker protecting the wire. Consider that an
ordinary 1500 Watt space heater draws about 12.5 Amps. If that heater is on
a circuit that has a 20 Amp breaker that leaves 7.5 Amps at 120 Volts or 900
Watts of heat available to start a fire before the breaker will trip. This
is plenty of power when concentrated in a small spot such as a loose
connection or corroded connector to make a swell fire. The proof is the
prevelance of dock cord fires at either end of the cord even though there are
breakers installed to prevent overload of this wire.
In summary, fires can occour even when the current in the line is below the
breaker or fuse rating. It happens often ashore, especially in the
wintertime.
Norm
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