Thanks to everyone for your responses, both on and off-list. You guys rock.
Allan, The system was originally installed in 2000 with an Ananda controller/disconnect box. The giant one with the mercury relays. It failed about 6 years ago and an MX-60 was installed to replace it. I agree that a modern controller is a no-brainer. I'd like to avoid having to replace the MX-60, but i don't see any way around it if I do a re-wire. To Ray's point, doing the string sizing exercise shows that a Classic 250 with 8 mods in series is probably the easiest solution, although there might be clipping in some circumstances. The existing MX-60 is in trouble for anything over 5 in series. -Luke On May 31, 2015, at 11:30 PM, Allan Sindelar <al...@sindelarsolar.com> wrote: > Luke, > I deleted your first message, but I thought you wrote that the system was > pre-MPPT, with strings wired as 4 12 Vnom in series. IT seems to me that > given insufficient Vmp, a modern controller is a no-brainer anyway, and it's > only a matter to which one to use. > > A Classic 250 is the easy route that lets you solve a major problem with a > simple and sensible component upgrade. It'll cost the customer nearly as much > for a winter return trip to estimate Voc. > But I agree with Jay and Randy: first check the existing array for failures. > Allan > > Allan Sindelar > al...@sindelarsolar.com > NABCEP Certified PV Installation Professional > NABCEP Certified Technical Sales Professional > New Mexico EE98J Journeyman Electrician > Founder (Retired), Positive Energy, Inc. > 505 780-2738 cell > > > On 5/31/2015 11:22 PM, Luke Christy wrote: >> Allen, >> With 8 modules in series I think I'll be looking at a Classic 250 for sure >> to be comfortable with winter morning VOC. >> I don't really know what kind of combiner situation I'll find up in the >> attic. It may be easy enough to re-wire into strings of 6 instead of strings >> of 8, though that is still probably going to push me just over the 150 VOC >> hard limit of the MX-60. I may not be able to get around replacing the >> controller. >> >> -Luke >> >> >> >> On May 31, 2015, at 10:59 PM, Allan Sindelar >> <al...@sindelarsolar.com> >> wrote: >> >> >>> Jay, >>> Whoa, I'd be careful there. Unless there's been a change while I was away >>> on my bicycle, Outbacks are still 140V rated maximum voltage and 150V hard >>> maximum. 142Voc in May suggests that doubling strings in series will easily >>> exceed max Voc in winter. That's why I previously suggested Classic 200 or >>> 250. Am I missing something? >>> Allan >>> >>> Allan Sindelar >>> >>> al...@sindelarsolar.com >>> >>> NABCEP Certified PV Installation Professional >>> NABCEP Certified Technical Sales Professional >>> New Mexico EE98J Journeyman Electrician >>> Founder (Retired), Positive Energy, Inc. >>> 505 780-2738 cell >>> >>> >>> On 5/31/2015 2:23 PM, jay peltz wrote: >>> >>>> HI Luke, >>>> >>>> To add here. I'm unclear if you have measured each string or the whole >>>> array at 71v. >>>> I would check each string for voc/isc. >>>> >>>> And then if they are consistent, I agree that putting 2 strings in series >>>> with a new controller might help out. >>>> You can try it with the MX-60 as you are at only 142v. If it works better >>>> then a new higher voltage CC would be required for winter higher voc. >>>> >>>> Let us know what you find out. >>>> >>>> jay >>>> >>>> >>>> >> Luke Christy >> >> NABCEP Certified PV Installation Professional™: Certification #031409-25 >> NABCEP Certified Solar Heating Installer™: Certification #ST032611-03 >> CoSEIA Certified PV Installer >> >> Solar Gain Services, LLC >> PO Box 531 >> Monte Vista, CO. 81144 >> >> sgsrenewab...@gmail.com >> >> 719.588.3044 >> >> www.sgsrenewables.com >> >> >> >> >> >> >> >> >> >> >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> List Address: >> RE-wrenches@lists.re-wrenches.org >> >> >> Change listserver email address & settings: >> >> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> >> >> List-Archive: >> http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html >> >> >> List rules & etiquette: >> >> www.re-wrenches.org/etiquette.htm >> >> >> Check out or update participant bios: >> >> www.members.re-wrenches.org >> >> >> > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > Luke Christy NABCEP Certified PV Installation Professional™: Certification #031409-25 NABCEP Certified Solar Heating Installer™: Certification #ST032611-03 CoSEIA Certified PV Installer Solar Gain Services, LLC PO Box 531 Monte Vista, CO. 81144 sgsrenewab...@gmail.com 719.588.3044 www.sgsrenewables.com _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
