<html>
<body>
The QO breaker I saw fail was a disconnect switch for an Air 303.
The run from the battery bank was substantial, and the wire was number
10. At the time, I calculated the amperage available (I
-V/R) and the short circuit current available was not close
to the 5000 amp AIC of the breaker for its DC rating.<br><br>
At 06:13 PM 5/16/2010, you wrote:<br>
<blockquote type=cite class=cite cite="">Voltage is not the issue here,
it is current, and battery fault currents can be staggering - far more
than one would ever encounter in a typical AC system fed from a
distribution transformer. I have seen a 200A Class T fail to act on
an 48V inverter fault which resulted in welding the metal tabs of the
fuse holder (which had been greased with copper-laden Penetrox E) to
their sockets. That indicates a fault current well north of 200,000
amps, quite possibly sseveral times that. A fire ensued,
which triggered the gas protection system and fortunately resulted in
almost no peripheral damage. It did cost about $10k to recharge and
recertify the Inergen system. The inverter manufacturer was quite
cagey on warranty replacement until they saw the photos - at which point
a replacement miraculously arrived by overnight air.<br><br>
<br><br>
On May 15, 2010, at 9:43 , Drake Chamberlin wrote:<br><br>
<blockquote type=cite class=cite cite="">I did see a QO breaker fail to
trip on a 24 volt DC system with only battery voltage behind it. It
burned a #12 wire completely in two. <br><br>
<br>
<blockquote type=cite class=cite cite="">The 48v is a max rating not a
nominal rating.<br>
So yes only good for 12 and 24v systems.<br><br>
However with CBI breakers I don't understand why the need for QO for DC
anymore?<br><br>
jay<br><br>
peltz power<br>
On May 15, 2010, at 6:28 AM, Rebekah Hren wrote:</blockquote><br>
<font color="#0000FF">Drake Chamberlin<br>
Athens Electric<br>
OH License 44810<br>
CO License 3773<br>
NABCEP </font><font size=1 color="#0000FF">TM
</font><font color="#0000FF">Certified PV Installer <br>
Office - 740-448-7328<br>
Mobile - 740-856-9648 </font></blockquote><br>
_______________________________________________<br>
List sponsored by Home Power magazine<br><br>
List Address: RE-wrenches@lists.re-wrenches.org<br><br>
Options & settings:<br>
<a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org" eudora="autourl">
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a>
<br><br>
List-Archive:
<a href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org" eudora="autourl">
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a><br>
<br>
List rules & etiquette:<br>
<a href="http://www.re-wrenches.org/etiquette.htm" eudora="autourl">
www.re-wrenches.org/etiquette.htm</a><br><br>
Check out participant bios:<br>
<a href="http://www.members.re-wrenches.org/" eudora="autourl">
www.members.re-wrenches.org</a></blockquote>
<x-sigsep><p></x-sigsep>
<font color="#0000FF">Drake Chamberlin<br>
Athens Electric<br>
OH License 44810<br>
CO License 3773<br>
NABCEP </font><font size=1 color="#0000FF">TM
</font><font color="#0000FF">Certified PV Installer <br>
Office - 740-448-7328<br>
Mobile - 740-856-9648 </font></body>
</html>