Hi Bruce, Unless you are leaving something meaningful out of your description, the AHJ is wrong. Your description is fine as far as the code goes. I recommend installing a 100A main in the new 200A panel for local disconnect @ house. Leave 100A main & feeder as-is (assuming safe, properly sized feeders, suitable grounding, etc.). There is nothing in the code that says you have to use identical size breaker to the buss rating. Try explaining it to the AHJ this way: Take the solar away from the question. The 100A main breaker determines the MINIMUM rating of the feeders and busbars. The busbars and feeders determine the MAXIMUM rating of overcurrent devices. For example, using the AHJ logic, you would be prohibited from using a #2 for feeder conductors between the 100A main and the house because they are rated for up to 130A. Doesn't make any sense, huh? The extra ampacity in the bussing is permitted and provides additional safety. Best of luck! Matt Lafferty
_____ From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Mendocino Solar Service Sent: Friday, July 31, 2009 9:57 AM To: RE-wrenches Subject: [RE-wrenches] down-sizing main breaker Hi Folks, Can anyone provide code reference or advice on this question? Our customer has 100 amp service at the meter pedestal, 100 amp main breaker feeding 200 foot underground run to a 100 amp panel at the house. We need to land a 40 amp breaker, so are proposing to replace main panel at house with 200 amp panel. The AHJ says we need a 200 amp main breaker in this panel, which will work, but says this requires upsizing the feeder, main breaker at meter, and therefore utility service to 200 amps. I've read on this list and elsewhere about downsizing the main breaker in a panel to create capacity to make the 120% rule. This AHJ says you can't put in a breaker smaller than the panel size, and furthermore, everything upstream would have to be upsized. Is this from the code? Bruce Erickson Mendocino Solar Service PO Box 1252 Mendocino, CA 95460 707-937-1701
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