Hans, It is not correct that you will have twice the disconnects necessarily. Most switches require passing through the disconnect twice. This must be done on the one ungrounded conductor for grounded systems, or the two ungrounded conductors with ungrounded systems. It is a circuit and it simply must be broken twice in series simultaneously to reduce the arc voltage on each switch opening to exactly half.
All 600V disconnect combiners use multiple poles so there would be no difference at all with these devices--only twice as many fuses--not a really big deal considering the huge safety advantages of ungrounded arrays. Bill. -----Original Message----- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Hans Frederickson Sent: Monday, October 04, 2010 9:16 AM To: 'RE-wrenches' Subject: Re: [RE-wrenches] Tranformless inverter Ryan, Yes, there are twice the number of ungrounded conductors, so twice as many fuses and switches are required. I haven't seen much in the way of combiners for ungrounded systems... A combiner for an ungrounded system has two fused ungrounded sections instead of the typical combiner of today which has fuses on the ungrounded input conductors and just a terminal block for all the grounded conductors. -Hans -----Original Message----- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Ryan LeBlanc Sent: Saturday, October 02, 2010 10:52 AM To: re-wrenches@lists.re-wrenches.org Subject: Re: [RE-wrenches] Tranformless inverter Bill, Specifically, the additional fusing and disconnect requirement you mentions. Is that each positive and negative PV Source and Output Circuit must have OCPD and go through switched? Twice the combiner boxes, fuses and switches? Thanks, Ryan J. LeBlanc NABCEPT Certified Solar PV Installer Cell: 707.591.1950 Direct: 707.536.9839 r...@naturalenergyworks.com http://www.NaturalEnergyWorks.com Ungrounding the array requires additional fusing and disconnects, but the most significant difference is that the module wiring and all external cable must be PV Wire/Cable. Therefore only modules with PV Wire/Cable can be used in these systems. You must confirm from the manufacturer that they have made the switch. Hopefully all manufacturers will be installing PV Wire/Cable soon so that this will not be a problem anymore. _______________________________________________ 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 _______________________________________________ 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 _______________________________________________ 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
