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<div class="moz-cite-prefix">We'd need more info to figure this out.<br>
1) Wire Size<br>
2) Type of charge controller C 60 or new MPPT model<br>
3) use a clamp on meter to measure actual current<br>
4) measure voltage drop across the breaker.<br>
<br>
This very well could just be a loose connection at the breaker
either the cable side of the breaker, or where it snaps on to the
buss bar.<br>
I've had QOs not work at higher voltage DC. (over 50 v) I'd have
to wiggle the breaker to get good contact on the buss, and it
would start working again. Given the age of the system, there's
probably some corrosion and dust on the contact points. Might
just need some sanding/ filing. <br>
The heat described fits with a loose/ high resistance connection.
<br>
Switching to a Midnite/ Outback breaker would be the only real way
to reliably make sure it doesn't keep happening though. On old
systems, our job is to exorcise the ghosts from the machine. <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 7/9/2013 9:10 AM, jay peltz wrote:<br>
</div>
<blockquote cite="mid:09ADFA12-C61A-4D50-9DA1-ED61824CFF54@asis.com"
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<div>Hi Dan</div>
<div>I'm guessing the wire can handle the 100 amp if they are
already running 60a. </div>
<div>I've had QO breakers go bad, even ones not tortured like that
one. </div>
<div><br>
</div>
<div>The derate is interesting as it has to do with less atoms of
air per volume. Less air, equals less cooling</div>
<div><br>
</div>
<div>Jay</div>
<div>Peltz power<br>
<br>
Sent from my iPad</div>
<div><br>
On Jul 8, 2013, at 10:07 PM, Dan Fink <<a
moz-do-not-send="true" href="mailto:danbob88@gmail.com">danbob88@gmail.com</a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div>
<div dir="ltr">Esteemed Wrenches;
<div><br>
</div>
<div style="">A weird troubleshooting call today for my
business partner DanB. I wish I had been along if only for
shock and awe and lessons learned.</div>
<div style=""><br>
</div>
<div style="">
A nicely installed vintage 12VDC PV system that someone
else designed and installed over 10 years ago, we replaced
a dead/frozen battery bank a month ago. DanB went back
today because customer reported low battery bank voltage.</div>
<div style=""><br>
</div>
<div style="">He found the PV input breaker tripped, a
Square D QO 2-pole 60 amp. About 600 watts of PV 12vdc
nominal on the roof. Reset the breaker, and a few minutes
later it was too hot to touch.</div>
<div style=""><br>
</div>
<div style="">So our working theory -- the 60a QO on *DC*
has a 1.2x ampacity derate, which puts 600w PV right at 60
amps instead of 50. There's also a bit of a high altitude
derate, which I don't understand at all. And during the
battery disaster last year bank voltage was certainly
11vdc or less, and was a bit over 11vdc on DanB's arrival
since the PV had not been charging. That puts us at
possibly 65.5 amps. The breaker was maybe just doing its
job correctly, though the heat was disturbing I am told.Or
maybe it got damaged during the battery disaster......both
+ and - were connected thru the 2 poles.</div>
<div style=""><br>
</div>
<div style="">In any case, our question --- due to my fuzzy
memory and poor shopping skills, we have a 100 amp QO 2
pole breaker in stock that needs a home, and it'll plug
right in. I have a nice tech bulletin from Schneider
Electric about DC ratings of their breakers that doesn't
show that a 100a QO 2 pole even exists, and a Schneider
FAQ that says it'll work fine:</div>
<div style=""><a moz-do-not-send="true"
href="http://www.schneider-electric.us/sites/us/en/support/faq/faq_main.page?page=content&country=US&lang=en&id=FA125383&redirect=true">http://www.schneider-electric.us/sites/us/en/support/faq/faq_main.page?page=content&country=US&lang=en&id=FA125383&redirect=true</a><br>
</div>
<div style=""><br>
</div>
<div style="">Any advice on this? We'd sure love to just
drop by and pop in the new 100a amp QO breaker instead of
installing a whole new DC rated Midnite box. But we don't
want to leave a fire hazard either. With 15 years service
on our local volunteer fire department, It would be
rather embarrassing if a "fix" we made to this old
off-grid system caused a fire. ;-) We are aware of the 5k
AIR issue with these breakers, but the battery bank is
small enough I don't think it's quite up there, and
information on AIR interruption from battery manufacturers
is hard to find......and of course it's a weird curve.</div>
<div><br>
</div>
<div>Thanks in advance;</div>
<div><br clear="all">
<div>Dan Fink,<br>
Executive Director;<br>
Otherpower<br>
Buckville Energy Consulting<br>
Buckville Publications LLC<br>
NABCEP / IREC accredited Continuing Education Providers<br>
970.672.4342<br>
<br>
</div>
</div>
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