If you backfeed a new breaker added to the top bus, it is a supply-side connection. The bus bars in the top are exposed to the full fault current capacity of the utility drop. You wouldn't be limited by the 120% exception.
Or you can backfeed a breaker on the bottom bus, and then it is a load-side connection. The main breaker for this subpanel would be the 60 A breaker in the top. The 120% rule applies. Scott On Oct 28, 2010, at 5:19 PM, Dana Brandt wrote: > Hi everyone, > > I'm working on two systems for homes that have the old style breaker panels > with no single main breaker. Instead, they have six breakers in the upper > part of the panel each labeled "main breaker," which satisfies the six > disconnect rule. The bus bar is split, with one of the six upper breakers > (60A) feeding a separate bus in the lower half of the panel. It appears that > the upper bus is rated for 200A, and the lower at 100A. The sum of the main > breakers does not exceed the 200A rating of the upper bus. There are spare > breaker slots on both the top and bottom buses. How do I deal with 690.64 (B) > (2) when there's no main breaker? > > Thanks! > > Dana > > Dana Brandt > Ecotech Energy Systems, LLC > www.ecotechenergy.com > d...@ecotechenergy.com > 360.510.0433 > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > 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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