This is interesting, because once again the normal electrical protection systems assume an almost infinite current supply to work properly, which is obviously not true for many solar applications. I've seen sustained series arcs that were current limited by the load, and therefore lower than the fuse rating, still turn relay contacts into molten blobs that dripped onto other equipment.
On a separate note, Julie Haugh should be on the Wrenches list, she has a wealth of info to offer us. Its our loss, that she's not being allowed on currently. Thanks, R. Walters [email protected] Solar Engineer On Apr 6, 2010, at 11:02 AM, Michael Welch wrote: > >>> Since the topic of AFI's has come up I wonder if anyone has actually tested >>> one, even an AC one. >>> >>> From what I've read from some tests on the Mike Holt site for AC breakers >>> is that they couldn't get them to work at anything less than standard ISC >>> for the breaker. >> >> I've not tested them, but I have read every patent on AFCI technology I can >> get my hands on. >> >> They don't sense that the load is arcing, in the sense -- say -- of an >> electric motor which arcs because of how the brushes work, or any number of >> other loads which arc. What they detect is arcing current well above the >> rated ampacity of the circuit breaker. A "series" arc, where the arc is >> passing through a load, is limited to the load itself -- a 12 amp rated >> vacuum cleaner makes, maybe, a 12 to 15 amp spike when it arcs. A >> "parallel" arc, where the arc is passing directly from line to neutral, or >> line to ground (not all AFCIs include ground-fault detection), will conduct >> up to the current available from the transformer. However, because it is >> not a constant load, it doesn't trip the over-current protection of the >> breaker, the arc just sits there until either it self-extinguishes or it >> causes a fire. >> >> There have been a lot of discussions on Mike's board about how useless AFCIs >> are. In the case of RE systems that have significantly less available >> current (maybe 50 or 100 amps, rather than hundreds to thousands), it's >> unlikely that a standard AFCI would "see" a high enough current to decide >> that a "parallel" rather than "series" arc was happening. But if the AHJ >> wants them, the AHJ gets them ... >> -- >> Julie Haugh >> Senior Design Engineer >> greenHouse Computers, LLC // jfh at greenhousepc.com // greenHousePC on Skype > > _______________________________________________ > 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 > > _______________________________________________ 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
