We occasionally run into a dual headache: a congested AND underpowered service panel.
Case in point a 100A Zinsco main panel with no room for a two pole breaker for inverter back feed. Normally we pull two 20A/120V branch circuits out of the main panel into a subpanel, back feed the subpanel with the inverter output and feed the main panel from the subpanel. The inverter in question is a SMA SB4000. Minimum over current protection is 16.66A (e.g. 20A continuous duty breaker). Otherwise protection needs to be 20.83A (e.g. 25A regular breaker). So we installed a 100A subpanel, pulled in the two 20A circuits, backed this subpanel with the inverter via a 20A continuous duty breaker, and fed the main panel via #8 wire and a 40A breaker. The inspector has a problem with this approach. Doesn't have a problem with the 20A breaker in the subpanel, but he objects to the 40A breaker in the main panel. His reasoning includes applying NEC 790.64(B). I believe the last sentence of (B)(2) stipulates that the breaker back feeding the subpanel is the one that counts, not what eventually what breaker back feeds the main panel. This inspector also has a problem with the production meter we installed. He wanted to see the "UL Listing" on the meter. I called Austin International (our vendor) about the meter in question (Itron Centron C1S) and they said that UL doest test meters as they (normally) are not used on the customer side of the service. Is there another listing for meters that would satisfy a nit-picky inspector? To make matters worse, we now have in stock both Itron Centron C1S meters as well as Schlumberger Centron C1S meters. Did Schlumberger buy out Itron? Or vice versa? Any help on the main panel calculation and acceptable listings for meter would be greatly appreciated. Peter T. Parrish, Ph.D., President California Solar Engineering, Inc. 820 Cynthia Ave., Los Angeles, CA 90065 CA Lic. 854779, NABCEP Cert. 031806-26 [email protected] Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] 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
