I've also seen failures/ nuisance tripping due to loose connections at the breaker. The heat then wreaks havoc on the breaker internals.
R. Walters [email protected] Solar Engineer On May 17, 2010, at 8:23 AM, jay peltz wrote: > HI Drake > > I don't know if this could apply to your situation, but I've seen the QO/QOU > fail from debris getting into the breaker itself. > Around here there are insects that deposit mud into small openings, like on > those breakers. > I've seen this cause the breakers to fail. > > jay > > peltz power > On May 17, 2010, at 7:02 AM, Drake Chamberlin wrote: > >> 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. >> >> At 06:13 PM 5/16/2010, you wrote: >>> 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. >>> >>> >>> >>> On May 15, 2010, at 9:43 , Drake Chamberlin wrote: >>> >>>> 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. >>>> >>>> >>>>> The 48v is a max rating not a nominal rating. >>>>> So yes only good for 12 and 24v systems. >>>>> >>>>> However with CBI breakers I don't understand why the need for QO for DC >>>>> anymore? >>>>> >>>>> jay >>>>> >>>>> peltz power >>>>> On May 15, 2010, at 6:28 AM, Rebekah Hren wrote: >>>> >>>> Drake Chamberlin >>>> Athens Electric >>>> OH License 44810 >>>> CO License 3773 >>>> NABCEP TM Certified PV Installer >>>> Office - 740-448-7328 >>>> Mobile - 740-856-9648 >>> >>> ___ > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: [email protected] > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org >
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