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<div class="moz-cite-prefix">Hey Bob;<br>
<br>
Can you share that AIC vs Voltage chart?<br>
<br>
Thanks,<br>
<pre class="moz-signature" cols="72">R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760</pre>
On 4/9/2013 1:46 PM, boB wrote:<br>
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<blockquote cite="mid:5164702D.2060909@midnitesolar.com" type="cite">
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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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