Hi Dana, "Sounds like" you have a lower-bus rated at 100A being fed by a 60A breaker... Yes? If so, technically speaking but not necessarily the right thing to do, you have a SWEET SETUP! In 690.64 terms, you are legally allowed 120A to feed that bus. Which converts to a maximum 60A PV interconnection breaker located at the opposite end of the bus from the 60A supply breaker. This is a panel configuration that I have wished was still made for many years. The downside is... It's probably older than me. With really wimpy buses. And really bad options for replacement breakers. And is full of 2-wire homerun circuits. If it doesn't have a perfect-in-every-way bus, it's time for a new panel. You also need to be able to buy real... Modern.... And New UL Listed breakers. Those gray looking replacement breakers in the home improvement store? They're NOT OK. In any way. Wadsworth? FPE? Bulldog? &...??? These panels are NOT OK for interconnection at this point. Time to upgrade. Yes, really. Zinsco? Depends. Any panel with signs of arcing around the bus anywhere? Better have a damned good explanation before I'd be tying in some PV. I know of a couple. Warped breakers? Change it! I just got done doing a 90% rewire on a friend's house and it tore my heart out sending the panel to the recycler. (This friend is into long-term thinking and sustainable everything. I would have left it if I could and so would they.) The bus was pristine. It is rumored that Al Capone used to stay in this place when he was in the area. The panel was giant, with lots of room. This panel had a coolness factor off the charts. But... I couldn't reliably get trustworthy breakers. And it was my friend's house. Somebody I care about. I couldn't leave it in there. I use the same judgement whether my customer is a friend or not. If what you have is a modern panel, share! I know I would personally appreciate it if you were able to share mfr, model, pictures, etc. Whenever we are upgrading/swapping/moving a service panel, we need to be installing something that provides the best opportunity for interconnection of distributed resources. We don't have those at this point. And we need them. A split-distribution (not just split-bus) service panel is one way to accomplish this. The trick is to limit the possible size of the breaker feeding the "2nd" bus (the lower bus in this case). It's not rocket science.
I'd be happy to use and publicize a product that a mainstream manufacturer came up with to deal with this. How about you? $0.02001, Solar Janitor PS - Home rewiring for friends only. I love doing it, but I do it for love. There ain't no amount of money that makes me want to do it just for money! _____ From: [email protected] [mailto:[email protected]] On Behalf Of Dana Brandt Sent: Thursday, October 28, 2010 5:19 PM To: RE-wrenches Subject: [RE-wrenches] backfeeding "six disconnect" panel 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 [email protected] 360.510.0433
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