ST inverters [RE-wrenches]

[Bob-O Schultze, Electron Connection]

<x-flowed>Steve, ETAL,
Thanks Steve, for sharing your conversations with Trace. It's easy 
for a manufacturer or distributor to say install it now and we'll fix 
it later. Unfortunately, even if that is completely true, it's at the 
Wrench level that the rubber meets the road-literally. It's an extra 
service call for us and who pays for our time and mileage? Trace? Not 
yet anyway. The distributor? Not bloody likely. The customer? Hardly 
fair, is it? And that leaves......


Bob-O

>
>The ST normally tracks the solar irradiance fairly accurately, when a cloud
>passes over the output drops proportionally. The LCD meter is powered solely
>from the array output, no AC backup power. The ST will disconnect from the
>grid if the grid voltage goes out of the window of acceptance. UL 1741
>requires a 5 minute timeout before reconnecting.
>The cooling fan comes on at about 200 watts of output; it is controlled by
>output, not thermally controlled. (This may change with future versions of
>the ST.)
>
>Here is the situation with the dealer's system. There are two 2300-watt
>arrays with an ST2500 for each array. To date, the ST as generated up about
>1,800 watts of output from each array.  The LCD indicates that the ST
>intermittently cycles OFF-ON at around 600-700 watt output level. The unit
>does come back on.  It appears that the LCD can, under some circumstances,
>"lock-up". During the lock-up the LCD only displays  "Rev 3".  So far Trace
>has not been able to recreate this "lock-up" even with a unit that suffered
>from intermittent lock-up in the field. Trace is still studying the problem.
>Perhaps there are some sensitivities to installation environments, like
>inductive coupling to a parallel high voltage line at the site.
>
> >From conversations with the Trace engineers, the occasional, intermittent
>cycling seems to be caused by the ST's MPPT algorithm being a little too
>aggressive in tracking the mpp on the knee of the IV curve. It appears that
>with certain modules, under certain conditions, the algorithm can over-shoot
>the knee of the curve. Trace is actively studying any occurrences of this
>problem. If and when a new algorithm is released, it will be field
>upgradable with a single replaceable chip.
>
>The Trace engineers have been very helpful and responsive with this
>situation. They are very willing to help with any problem ST installations.
>They both want help get the system running and they are learning about
>unexpected glitches and quirks that can occur with any new product release.
>
>Several dealers have asked my opinion about the ST inverters. I advise them
>the ST (Rev.1) like any other first release product, is very likely to have
>some quirks and problems that occasionally show up. If I were to
>sell/install any newly released, Rev.1 product, I would advise the customer
>that "the product is a first generation product and there may be some
>unexpected quirks. That both I (the dealer) and the factory will stand
>behind the product and will work to resolve any problems that might occur."
>If the customer (or you as the dealer) are not comfortable with that
>arrangement and understanding, then they should either choose another
>produce or wait until the new product has proven itself in the field
>(perhaps with a few up-grades or expanded installation guidelines).
>
>I hope this helps shed some light on the current situation with the ST
>inverters. If any of you dealers are having problems with STs that you've
>installed and your distributor can not help to work with Trace, please
>contact me and I will see what I can do to help.
>
>Sincerely,
>Steve Bell
>SunWize Technologies
>815-256-2222
>sebpv at stelle.net

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