Hi Wrenches -
I posted this original thread a ways back but we've now had the opportunity to fix the problem... What I had failed to mention in my original post (below) is that this is an off grid Sunny Island based system. The Sunny Island wasn't properly setup and thought that the battery bank was full so it was telling the Sunny Boy to throttle back (I believe by adjusting the AC frequency). Anyway, we reprogrammed the Sunny Island with the correct battery setup and the system is now cranking. Once the battery bank is full and if the loads go down the Sunny Boy will in turn crank down its output which is just what we want it to do. Thought I'd let you know - I guess that goes to show that I haven't done any off grid work for a long time (since the late 90s)! -August ---------- Forwarded message ---------- From: *Darryl Thayer* <daryl_so...@yahoo.com> Date: Thu, Feb 3, 2011 at 4:59 PM Subject: Re: [RE-wrenches] Odd Inverter Behavior To: RE-wrenches <re-wrenches@lists.re-wrenches.org> I have seen that behavior almost. if open cirucit is 330 then MPPT should be about 264 which is to close to bottom of the window. Last summer a sunny boy in a similar situation of 8 modules in string was droping out on MPPT tracking. The inverter had additional module added and started to behave correctly. Sometimes the manufacture wants the sale and some inverters might not be in spec, so becarful of string sizing calculators. Another case the tracking algorithm was defective and the modules were operated at to high a voltage above the Vmp voltage, I replaced the inverter and problem fixed. ------------------------------ *From:* August Goers <aug...@luminalt.com> *To:* RE-wrenches <re-wrenches@lists.re-wrenches.org> *Sent:* Thu, February 3, 2011 6:01:11 PM *Subject:* [RE-wrenches] Odd Inverter Behavior Hi Wrenches - We were called out today to check out an under performing system installed by another contractor. This is an odd case. The system has 24 Suntech 180s in three strings of 8 and a SMA Sunnyboy 4000us. Open circuit voltage for each string was about 330 Volts and we verified that everything appeared to be wired in correctly. There is no DC side grounding at all. Just a positive and negative coming down off the roof for each string. With all modules in direct light the inverter is only pumping out about 250 Watts steady state. We noticed that when we turn it off and on again that the power went up to about 1500 Watts as it started tracking the max power point. Then it slowly veers off course and settles out at about 250 Watts and is running very close to the open circuit voltage of about 330 volts. I would expect the MPP voltage to be closer to ~280 Volts. The inverter MPP tracking range goes down to 250 Volts so I don't think that's the problem. Anyone ever seen anything like this before? What might be causing the inverter to get confused? The only thing I can think of is that something fishy is going on with the lack of a DC side ground and that certainly needs to be fixed anyway. All thoughts welcome. Best, August _______________________________________________ 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 -- August Goers Luminalt Energy Corporation 1320 Potrero Avenue San Francisco, CA 94110 O: 415.641.4000 M: 415.559.1525 aug...@luminalt.com
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