Re: [RE-wrenches] SW4024 relay spark issue

[Allan Sindelar]

Ray, Yes, I know... Doesn't ten years seem a bit weak on a set of Surrette's best? And the other ten cells are remarkably even. If replacement (which is already being arranged by Surrette in a good way) gives 3-5 more years, even with keeping a close eye on cell variations, we have accomplished a reasonable objective. Re a loose connection: this is why I posted the questions: to look for other possible explanations. Did you see Nick's response: "I used to see that arc flash all the time from the SW series relays, even on new SW Series inverters.  That always happened when the contact switched under load." I'd consider this before pulling the cover off to look for the source of the flash. Re the single-string issue, Steve Higgins replied very promptly (as did James Surrette, to whom I had written before posting here), saying " What you can do to save some fuel is pull the two cells out and reduce charge voltage per cell… this means if your absorbing at 28.8, then you adjust the voltage down 2.4vpc to 24vdc… If you do this you may also want to adjust the LBCO as low as possible.   If you leave the dead cells in it’s just going to consume more fuel to keep charged." But we agreed that the new cells would be in place soon enough to not justify this course of action. I have done the one-string-from-two temporary solution many times over the years. Thank you, Allan Allan Sindelar al...@positiveenergysolar.com NABCEP Certified PV Installation Professional NABCEP Certified Technical Sales Professional New Mexico EE98J Journeyman Electrician Founder, Positive Energy, Inc. A Certified B CorporationTM 3209 Richards Lane Santa Fe, New Mexico 87507 505 424-1112 office 780-2738 cell www.positiveenergysolar.com   On 11/18/2013 6:13 PM, Ray Walters wrote: I thought the relays on the SWs were sealed, so visible arcing sounds bad.  Are you sure its not a loose connection? Also on the batteries, anytime I've ever seen someone replace just a couple of cells in a bank that old, it never ended well.  It was like that gopher stomping game, and you hit one problem, and then another pops up right after..... We need some kind of financing program for battery replacements, so that people can get what they really need: a whole new set. That very situation, is why I quit doing as many single series strings: one or two cells fail, and the whole system goes.  In this same situation with 2 strings, you create a single string of your strongest cells to limp the customer along, until they can afford to replace the set. As cells go down, you keep pulling in replacements from the retired string. This would be a great time to take a few of the best used cells from another aging set  on another system that is getting replaced. R.Ray Walters CTO, Solarray, Inc Nabcep Certified PV Installer, Licensed Master Electrician Solar Design Engineer 303 505-8760 On 11/18/2013 5:01 PM, Allan Sindelar wrote: Wrenches, A longtime off grid customer with a 1997-era Trace SW4024 and a Kohler 8.5RMY backup generator (with 1,800 hours over 16 years) has never had an inverter failure, but requested my assistance with a recent development. His generator has been set up on automatic operation using standard Trace voltage, quiet time and load-start program parameters. When it was called to run, it would charge to 29.6 V with a one-hour absorption, then shut off. This has worked well until recently. The automatic operation includes a cool-down and the modest absorption means that the AC input current at shutdown is going to be pretty low. Recently he called me because his generator was starting more frequently and running for longer duration. Of course, I immediately suspected the batteries, which are ten-year old 5000 series Surrette 4KS-25PS cells. Upon checking I found two weak cells, which would explain the inability of the batteries to reach full voltage and shut off after absorption. I will be replacing these two cells, which fortunately are both within the same red polypropylene case, as our only option, as the homeowner's budget won't allow replacement of the whole set. As a single string, the two new cells should play reasonably well with the old cells for a few more years. Because of this, the homeowner had recently shut off the generator at night using the buttons on the inverter, and when he did this he saw a spark flash from inside the inverter on the AC end. I was able to duplicate the flash, which I assume to be the AC2 input relay. The AC2 In setpoint is set to maximum 35A AC. Until the failed cells are replaced, I have advised the homeowner to manually control the generator at the generator, using its AC output breaker to disconnect the current to the inverter before the 108V AC default input voltage threshold causes the inverter AC input relay to unlatch under load. While the SW latches while unloaded and then ramps up input current, I don't believe that it can reduce input current to zero before unlatching when shutting down. My guess is that after 15 years of flawless performance, the relay contacts have pitted enough to cause arcing at disconnect, and if not addressed, the relay on the AC board will eventually fail. As AC relay boards these days are likely made out of unobtanium, I'd rather avoid this failure. So my questions, please: 1. Have I likely correctly identified the AC input relay as the most likely cause of the visible arcing when the generator is turned off at the inverter? 2. Should manual control be a permanent solution? 3. Any other suggestions for this customer? Thank you, Allan -- Allan Sindelar al...@positiveenergysolar.com NABCEP Certified PV Installation Professional NABCEP Certified Technical Sales Professional New Mexico EE98J Journeyman Electrician Founder, Positive Energy, Inc. A Certified B CorporationTM 3209 Richards Lane Santa Fe, New Mexico 87507 505 424-1112 office 780-2738 cell www.positiveenergysolar.com   _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address & 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

Change email address & 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