[RE-wrenches] SW4024 relay spark issue

[Ray Walters]

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*
> _Allan at positiveenergysolar.com_ <mailto:Allan at positiveenergysolar.com>
> NABCEP Certified PV Installation Professional
> NABCEP Certified Technical Sales Professional
> New Mexico EE98J Journeyman Electrician
> Founder, *Positive Energy, Inc.*
>
> A Certified B Corporation^TM
> 3209 Richards Lane
> Santa Fe, New Mexico 87507
> *505 424-1112 office 780-2738 cell*
> _www.positiveenergysolar.com_ <http://www.positiveenergysolar.com/>
>
>
>
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