NEC 310.4 permits parallel conductors of 1/0 or larger. Conductors smaller than 1/0 are permitted, but with stipulations.
Nick's assertion "most if not all of the current will flow on the larger wires" is incorrect. The current will be shared proportionately between two paralleled conductors commensurate with their individual resistances. The original query related to recreational vehicle PV DC-side installation, and referenced installation of a "second PV", implying only one existed initially. This would thus fall outside the bounds of the NEC, but shouldn't be interpreted to mean some of the common-sense aspects of the NEC aren't to be considered. Dan --- On Wed, 2/2/11, Jason Szumlanski <ja...@fafcosolar.com> wrote: From: Jason Szumlanski <ja...@fafcosolar.com> Subject: Re: [RE-wrenches] Parallel wire runs to increase size To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org> Date: Wednesday, February 2, 2011, 11:15 AM Nick, Can you cite a code section that supports this. (not challenging you – it makes sense and I agree) I have been wondering about SMA’s recommendation to parallel two 1/0 cables for a Sunny Island. If the wire sizes and lengths are identical, is this acceptable? Jason SzumlanskiFafco Solar From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Nick Soleil Sent: Wednesday, February 02, 2011 12:05 PM To: RE-wrenches Subject: Re: [RE-wrenches] Parallel wire runs to increase size You shouldn't parallel wiring that way. That is not acceptable by code, and it is unnecessary. If the #10 is not sufficient just replace it. Due to the fact that the larger wiring has much less resistance, most if not all of the current will flow on the larger wires. Nick Soleil Project Manager Advanced Alternative Energy Solutions, LLC PO Box 657 Petaluma, CA 94953 Cell: 707-321-2937 Office: 707-789-9537 Fax: 707-769-9037 From: "Starlight Solar, Larry Crutcher" <la...@starlightsolar.com> To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Sent: Wed, February 2, 2011 8:00:07 AM Subject: [RE-wrenches] Parallel wire runs to increase sizeWrenches, Some of our business involves repairing poor PV solar installations on recreational vehicles. So often we wind up installing a roof junction box and running a second PV to controller wire and then replacing the controller to battery wire size. For instance, we may find a 10 gauge wire run to the controller. We then add #8, #6, #4 or even 2 gauge and parallel to the #10 depending on power and distance of the run. My question: Is there a calculator or chart that will tell me what the combination of any two wire sizes equate to? example: #10 + #4 = X Thanks.Larry Crutcher Starlight Solar Power Systems powered by STARLIGHT™ -----Inline Attachment Follows----- _______________________________________________ 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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