We have avoided any load side code issues by doing supply side taps on older buildings. The AHJ typically turns a blind eye to the load side issues if we use this interconnection method. That is not to say that you shouldn't strongly encourage the owner to address the load side deficiencies or code violations, if any. Nonetheless, adding solar to the supply side of the main disconnect would not exacerbate any existing problems on the load side.
Jason Szumlanski Fafco Solar From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of JRQ Sent: Friday, December 23, 2011 3:51 AM To: RE-wrenches Subject: Re: [RE-wrenches] Landing into a sub-panel without a main servicepanel, just a main switch Yes, if there is a distribution block and several subpanels are fed from the same point downline from the main disconnect, then what I'm describing would not be applicable. The other subpanels function as loads with respect to the distribution block. The same if there are any taps on the load side of the main disconnect. We need to see a wiring diagram for how these subpanels are connected together to give a definitive answer. Jeffrey Quackenbush. ________________________________ From: Richard L Ratico <richard.l.rat...@valley.net> To: re-wrenches@lists.re-wrenches.org Sent: Friday, December 23, 2011 9:43 AM Subject: Re: [RE-wrenches] Landing into a sub-panel without a main service panel, just a main switch Jeffrey, On the load side of the Fused 200 Amp Service Disconnect there is a splice or splices or distribution block in the conductors which feed the 5 subpanels. It seems quite possible that one or more of those conductors or the distribution block could see the sum of the current from the grid and the current from the solar. A combination of loads in the 4 subpanels, other than the one backfed by the solar breaker, could overload the conductor or part of that conductor carrying that combined current, without necessarily blowing a main fuse or any of the breakers. The devil is in the details, in this case the size of the conductors and the way they are utilized. Ray has a point. It is possible there are existing code violations. These should be corrected in a manner which facilitates inclusion of the solar. Dick Ratico Solarwind Electric --- You wrote: The flow of electricity isn't two-way traffic along a conductor. If there are no loads on the conductor between the main system disconnect and the main breaker of a subpanel, in this scenario, there can only be up to 200 A coming from the utility OR up to 60 A coming from the solar system backfed through the subpanel. The intent of limiting the solar system size plus the utility source to 120%, or even 100%, of a bus or conductor rating is when that bus or conductor can potentially see current from both sources simultaneously, it could overheat if these sources exceed the bus or conductor rating. That's not physically possible unless there is a load in between both sources. --- end of quote --- _______________________________________________ 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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