[RE-wrenches] Odd Inverter Behavior

[August Goers]

Hi All -



Thanks for the ideas. It definitely sounds like should trying wiring in at
least another module in series to see how it acts.



Best, August







*From:* re-wrenches-bounces at lists.re-wrenches.org [mailto:
re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Warren Lauzon
*Sent:* Friday, February 04, 2011 5:55 AM
*To:* RE-wrenches
*Subject:* Re: [RE-wrenches] Odd Inverter Behavior



That 284 volt number is if the panel is at 25 degrees C. If the panels are
in full sun and with little wind, they can be higher temperature than that
even in cold weather.



An easy way to get a rough check on that is to disconnect the panels and
temporarily haywire an extra panel in series from another string. I suspect
the array might have to be rewired for 2 x 12.





*From:* August Goers <august at luminalt.com>

*Sent:* Thursday, February 03, 2011 5:01 PM

*To:* RE-wrenches <re-wrenches at lists.re-wrenches.org>

*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 at 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

Northern Arizona Wind & Sun - Electricity from the sun since 1979
--------------------------------------------------------------------
Online Solar Store <http://store.solar-electric.com/>
Free Solar Discussion Forum <http://www.wind-sun.com/ForumVB/>
--------------------------------------------------------------------
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20110204/2a24e4e0/attachment-0003.html>