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Wrenches,<br>
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.<br>
<br>
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.<br>
<br>
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. <br>
<br>
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.<br>
<br>
So my questions, please: <br>
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?<br>
2. Should manual control be a permanent solution?<br>
3. Any other suggestions for this customer?<br>
<br>
Thank you,<br>
Allan<br>
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<p class="MsoNormal"><b>Allan <span class="SpellE">Sindelar</span></b><br>
<span style="font-size:10.0pt"><a
href="mailto:Allan@positiveenergysolar.com"><u><span
style="color:#000099">Allan@positiveenergysolar.com</span></u></a></span><br>
<span style="font-size:10.0pt">NABCEP Certified PV
Installation Professional<br>
NABCEP Certified Technical Sales Professional<br>
New Mexico EE98J Journeyman Electrician<br>
Founder, <b>Positive Energy, Inc.<o:p></o:p></b></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt">A
Certified B <span class="SpellE">Corporation<sup><span
style="font-size:7.5pt">TM</span></sup></span><br>
<st1:address w:st="on"><st1:street w:st="on">3209
Richards Lane</st1:street><br>
<st1:city w:st="on">Santa Fe</st1:city>, <st1:state
w:st="on">New Mexico</st1:state> <st1:postalcode
w:st="on">87507</st1:postalcode></st1:address><br>
<b>505 424-1112 office 780-2738 cell</b><br>
<a href="http://www.positiveenergysolar.com/"
target="_blank"><u>www.positiveenergysolar.com</u></a><o:p></o:p></span></p>
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