As long as the solar breaker is not larger than panels main breaker there is no potential busbar overloading. The whole concept was created by a misinterpretation of what the bus rating actually is.
A review of this issue by qualified materials engineers will end this issue entirely. The breakers are thermally activated. What everyone is referring to as the buss rating is actually the tab rating. The buss is typically rated for 8 or more x the tab rating. A 200amp panel has a bus capable of safely handling a 1000amps. It has tabs (the things that connect the breakers to the bus) capable of safely handling 225amps. Here's the best part for those that don't already know this: Breakers are thermally activated, as the bus or the breakers heat up they derate. Pretty fail safe way to prevent a potential overloading issue if you ask me. As long as no breaker exceeds the tab rating and you limit your current SOURCES(utility and solar) feeding the panel to 2 it is impossible to overload the bus or the tab. Sky Sims Ecological Systems http://www.ecologicalsystems.biz 220 County Road 522 Manalapan, NJ 07726 732-462-3858 toll free)866-759-7652 fax)732-462-3962 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of jay peltz Sent: Wednesday, July 30, 2008 11:31 AM To: RE-wrenches Subject: Re: [RE-wrenches] Gray code area Hi Drake, do you know how this is all done in say Germany? I realize they have different codes ( hopefully) but how do they address the main issue of potential bussbar overloading? thanks, jay peltz power On Jul 30, 2008, at 10:24 AM, Drake Chamberlin wrote: > Thanks to All who have replied, > > First, to answer William's question > > "What is a "feed-through" breaker box and what are "feed-through" > lugs?" > > A feed through panel is the type of service equipment often > installed on pre-manufactured homes, where a main switch is needed > outside the building, and a limited number of loads, fed from the > outside, are also supplied. On the bottom of the busbar, there > are lugs equivalent to the lugs for the service entrance cables. > > This is useful when feeder is to be installed to supply the breaker > panel in the premise that is equal to the total service amperage. > No breaker is needed for the run to the subpanel inside, since the > wiring will be equivalent to the service cable. It is similar in > function to a disconnect switch, but will typically have 4 to 8 > breaker spaces. > > The situation in this project is that a feed through panel is in a > separate building from the building to be supplied from that > panel. The building this panel is in has a separate electrical > service, which is commercial. The service for the residence comes > in through a separate meter, located on this same commercial > building, then goes to the feed through panel. This panel was > installed for us, for the sole purpose of allowing a feed from the > solar array. > > The issue here is that the busbar will have 200 amps from the main, > and over 40 amps from the solar. No power is to be taken from the > residential service to feed the commercial building. There is no > possibility of an overload on the busbar because the house has a > main 200 A breaker that will limit the load from the panel. > > It could be argued that since the line to the house will have up to > 240 amps available on a 200 amp service, that is too much. I would > argue that a standard service drop can supply 10,000 amps > instantaneously. > > The box is strictly to be used as an AC combiner and feed for two > inverters. By the letter of the NEC, it does not seem to be code. > I'm going to use Kent's suggestion and use a label, after running > it by the AHJ beforehand. > > > -Drake > > _______________________________________________ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org http://lists.re-wrenches.org/listinfo.cgi/re-wrenches-re-wrenches.org List rules & etiquette: http://www.re-wrenches.org/etiquette.htm Check out participant bios: www.mrsharkey.com/wrenches/ _______________________________________________ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org http://lists.re-wrenches.org/listinfo.cgi/re-wrenches-re-wrenches.org List rules & etiquette: http://www.re-wrenches.org/etiquette.htm Check out participant bios: www.mrsharkey.com/wrenches/
