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Those 250 amp and 175 amp breakers we have used for many many
years now<br>
have an AIC of 50,000 amps at 125 volts and if you look at the
curve, at 48 volts<br>
they are around 100,000 amps. I think that this information is on
the label<br>
of the breaker.<br>
<br>
How many problems have you had with the Carlings or any other type
of<br>
those large breakers ?<br>
<br>
boB<br>
<br>
<br>
On 4/9/2013 10:40 AM, Michael Welch wrote:<br>
</div>
<blockquote
cite="mid:946180.52584.bm@smtp107.sbc.mail.ne1.yahoo.com"
type="cite">
If anyone would like an Acrobat version of this article, you can
find it
here:<br>
<br>
<a moz-do-not-send="true"
href="ftp://ftp.re-wrenches.org/pub/hp27_pg26_freitas.pdf"
eudora="autourl">
ftp://ftp.re-wrenches.org/pub/hp27_pg26_freitas.pdf<br>
<br>
</a>William Dorsett wrote at 07:00 AM 4/9/2013:<br>
<br>
<blockquote type="cite" class="cite" cite="">This topic comes up
often enough
that we ought to mention a yellowed article in Home Power, (1992
Issue
27, pg 26). Christopher Freitas wrote <i>Overcurrent Protection
for
Battery-Powered Systems </i>where he describes experiments he
did back
when he was with Ananda. He put a 2000 A Big Switch to initiate
a short
(4/0 cable) between the terminals on a set of four golf cart
batteries (2
strings @ 12V). In series, he put in a 500A Shunt so he could
measure
current passing and various fuses and breakers. “For comparison,
we
decided to directly short the battery…the meter read 6960 amps
peak
current (three seconds) …during each test the 4/0 cable lifted
off the
ground 4 inches into the air by the forces generated by the
extremely
high current..” They videoed the 250 A ANN buss fuses arc and
smoke; the
200A Heinemann Series AM breakers (paralleled ones that maybe
Roy
mentioned) went 3 seconds without breaking and the video showed
a flash
and blue smoke. <br>
175A ITE breaker with 42,000 AIC “simply tripped…but still
allowed a peak
current of 2960 amps<br>
200A Class T Littlefuse “opened promptly with no external signs
of
stress…1920 amps peak current”<br>
Christopher’s recommendations: <br>
“Every AE system must have overcurrent protection able to
interrupt the
maximum current available from the batteries. For most systems,
the main
protection should use current limiting high AIC fuses, such as a
Class T
or Class R. A disconnect switch which allows the fuse to be
safely
changed should be included. A lower cost alternative is to mount
the fuse
in a fuse holder without a disconnect. Although the fuse would
always be
electrically hot, it normally would not be changed during the
life
of the system. The fuse holder should be mounted outside the
battery
enclosure. Fuses should not be bolted directly onto the battery
terminal,
as they are not designed to handle the physical stresses that
can occur
without the protection of a fuse holder.<br>
<br>
Fuses which have exposed elements, such as ANN fuses, should not
be used
because they are not current limiting and have only 2500 amps
AIC. They
also may be a significant hazard when installed near batteries.
<br>
<br>
High AIC breakers, like the Heinemann Series CF (25,000 Amps AIC
@ 65VDC)
can provide overcurrent protection for individual items. They
cannot be
used to protect lower AIC breakers. This eliminates their use as
a main
disconnect in most systems. <br>
<br>
Low AIC breakers, like the Heinemann Series AM (5000A AIC @65
VDC) or the
Square-D QO (5000A @ 125 VDC) can be used in load distribution
centers
and components, but must be protected by a current limiting
fuse. Using
low-AIC breakers alone will not provide sufficient protection
with a
battery system and may be a significant hazard during short
circuit
situations.”<br>
<br>
It won’t pull up anymore on HP’s article search but probably
Michael has
a copy he could post for those interested.<i> <br>
</i> <br>
Bill Dorsett</blockquote>
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