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boB,<br><br>
SMA does recommend protecting Sunny Islands with a fuse on the battery,
even though the breakers on the units are rated for 10,000 Amps.
Are the SI breakers inferior others you have mentioned? <br><br>
Thanks,<br><br>
Drake<br><br>
<br><br>
At 12:14 AM 4/10/2013, you wrote:<br><br>
<blockquote type=cite class=cite cite="">After 100's of thousands
of inverters having been shipped in the last many years<br>
and thousands of inverters broken and shorting the battery terminals,
there has<br>
never been (to our knowledge) one breaker that has not tripped.<br><br>
The Midnite site lists the AIC rating of all our breakers I
believe.<br><br>
The Carling F series of Magnetic-Hydraulic breakers poop sheet is
here...<br><br>
<a href="http://www.carlingtech.com/sites/default/files/documents/F-Series_Details_%26_COS_0.pdf">
http://www.carlingtech.com/sites/default/files/documents/F-Series_Details_%26_COS_0.pdf</a>
<br><br>
I guess there isn't a graph of AIC vs. voltage on their F series web page
but we remember<br>
them showing us figures or a graph that says those breakers have an AIC
of more than<br>
100,000 amps at 48 volts. We'll try to find that info or you may be
able to get that<br>
from Carling.<br><br>
I have, many times, directly connected these breakers across good L-16
battery strings<br>
to demonstrate the left-hand rule to people where the 4/0 cable jumps
apart or towards each<br>
other when very high current passes through those wires when they are
near each other.<br><br>
It always trips. Never tried it at anything above a 48V battery
banks IIRC.<br><br>
Robin would like to mention that anyone that wants to use T-Classc
fuses.... Welcome back to the 1990's<br><br>
boB<br><br>
<br>
On 4/9/2013 1:23 PM, Ray Walters wrote:<br>
<blockquote type=cite class=cite cite="">Hey Bob;<br><br>
Can you share that AIC vs Voltage chart?<br><br>
Thanks,<br><br>
<pre>R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760</pre><font face="Courier New, Courier"></font>On 4/9/2013
1:46 PM, boB wrote:<br>
<blockquote type=cite class=cite cite=""><br>
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>
<blockquote type=cite class=cite cite="">If anyone would like an Acrobat
version of this article, you can find it here:<br><br>
<a href="ftp://ftp.re-wrenches.org/pub/hp27_pg26_freitas.pdf" eudora="autourl">
ftp://ftp.re-wrenches.org/pub/hp27_pg26_freitas.pdf</a><br><br>
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><br>
</blockquote><br><br>
<br><br>
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