Reality versus the "last" final stats. [RE-wrenches]

Jeff Clearwater clrwater at earthlink.net
Sun Apr 27 07:47:35 PDT 2003


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Hi John, Jeff Y. and All,

I'm glad John responded to Jeff Y.s survey so clearly and strongly. 
As much as I really appreciate Jeff' Ys intent and the time he took 
to put together the survey and collate the results, I too thought the 
method was flawed in its conclusions.   As an informal survey to see 
the data, I thought it valuable but when those results were 
translated to statistics  - I think it did not serve us.

It's likely that one would get more responses from wrenches with 
failures than those without and that his definition of "failure" was 
much too strict.  The Wrenches list is a wonderful list but not a 
scientifically significant sampling set to hang a inverter 
manufacturer's reputation on.

So thanks again to Jeff's informal survey but I strongly encourage 
everyone to quote John's stats as the reality of the situation. 
Better yet let's focus as installers on eliminating those "failures" 
that turn out to be solvable in the field and rest assured that SMA 
is working with integrity - as they have consistently demonstrated - 
at reducing their mistakes.

It would be great if panel and inverter manufacturer's were proactive 
about publishing failure rate statistics so we wouldn't even feel the 
need to gather the info ourselves.  How about it John and all,  how 
about a regularly quarterly or yearly update on failure rates.  Those 
kind of open books could only increase our already high trust of your 
operation and improve our view of  others (are you hearing this 
Sharp, BP, Outback, etc?).

Peace,

Jeff C.
Village Power Design


>Wrenches:
>
>I have been out of town for a few days at, coincidentally, a DOE
>inverter reliability workshop.  Sorry I was not able to chime in here
>sooner.
>
>With all deference to Jeff, his experience is an anomaly which does not
>agree statistically with the installed base of inverters in the US.  I
>also disagree with his conclusions, his definitions, and his methodology
>for calculating reliability.  What I do know is that it is always the
>inverter's fault no matter the real root cause of the problem.
>
>I have not yet analyzed the data for 2003 yet but...  Other than the
>Firmware V8.65 / Vac_srr issue, which I think has been largely resolved,
>I do not see any patterns that would indicated that there is a
>significant change in the number of failures we are seeing.  What I can
>say, definitively, based on real data through the end of 2002 is:
>
>Our total return rate through 2002 for inverters sold in the US was
>4.3%.  Of these, about 15% have no problems found after they are
>returned. Not including the "no problems found" units, our actual total
>failure rate for inverters is 3.8%.
>
>The largest number of failures to date is 1.4% for the dreaded Vac_Srr
>error message with which many of you are all too familiar.  I am sure
>this will also be our largest failure related issue when we do the
>numbers for 2003. Unfortunately, we did not fully understand the problem
>for a couple of weeks and so there were more units than I would have
>liked that made it into systems.  We retested and reworked many
>inverters here at SMA America and recalled all the ones we could track.
>We also did our best to get the word out to try to find the others we
>could not track in an effort to solve the problems as quickly and
>painlessly as possible for all concerned. 
>
>For those not aware of this problem: 2500's with version 8.32 and 8.66
>firmware are fine.  Units with 8.65 firmware can trip off line at too
>low a voltage and will display a characteristic error message Vac_Srr.
>These units can be upgraded in the field with new firmware which we
>supply at no charge. We estimate that the firmware fix will solve the
>problem in about 80% of the cases but that some units will need to come
>back here for replacement of two small capacitors.  Contact Jason Mills
>if you have any questions or need help with Vac_Srr issues. 
>
>This leaves a remaining failure rate of 2.37%.  Of this, the most common
>failures are:
>0.50% - Unknown failure reported by the user - troubleshooting
>inconclusive. 
>0.51% - Vac_Bfr error message.  This related to a bad batch of ceramic
>surface mount capacitors that developed micro fractures typically after
>a few days or weeks of thermal cycling. We changed capacitor vendors and
>the problem has disappeared. 
>0.31% - Ground fault will not clear.  More than half of the "no problems
>found units" were returned for ground faults.  We believe this indicates
>a lack of understanding of ground faults and how to troubleshoot them.
>Some of these were caused by wires that were loose or could have been
>damaged during installation.  Others had dead current sensors that could
>have been defective or were destroyed by replacing the 1 amp fuse with a
>larger size before clearing the ground fault.
>0.39% - EEPROMD This failure occurs when the end of day data is
>corrupted as it is written from the inverter's RAM into Non-volatile
>ROM. There is a simple in field reset procedure that solves the problem
>and once solved they do not appear to reoccur.  This cause of this issue
>is not well understood but the next version of the inverter firmware
>will automatically reset the error.
>0.17% - Failed IGBT's/caps. Typically an over voltage failure caused by
>incorrect installation.  We have seen 3 units to date that look like
>failures due to lightning.
>0.10% Broken cover screws.  All units now ship with greased screws and
>the case was reworked to make misalignment during initial assembly less
>likely.
>0.09% - DOA  usually a power supply issue.  40% of these units had no
>problems found and were never powered up.  Probably caused by low PV
>voltage.
>
>The remaining failures (0.3% total) are all below 0.1% and are
>essentially random production related events.  K1 open, broken
>terminals, melted ac fuse holders, over current failure, noisy, bad temp
>sensor, etc.
>
>In much this failure analysis we did not differentiate if the failure
>was production related or likely precipitated by the installation.  The
>one notable exception is over voltage failures where the inverter is
>essentially destroyed. Another important thing to point out is there is
>a wide disparity of the failure rate depending on the installer.  We are
>in a newly emerging market and the installer's level of experience with
>our inverters clearly has an impact on the in-field failure rates.  Some
>wrenches out there have installed many sunny boys with very few problems
>others have seen a much higher failure rate on a much smaller sample
>size.  Some times the failures come in clusters and are, IMHO, an
>unfortunate bad luck of the draw issue. 
>
>To close: Every inverter undergoes numerous quality tests during
>manufacture In addition, every inverter is functionally tested on an
>automatic burn in rack before it leaves the factory.  We take failures
>seriously and take corrective action to remedy the situation as quickly
>as possible.  We address problems openly and factually to the best of
>our knowledge and will continue to do so.  I encourage all of you to
>provide us with feed back so that we can continue to improve our
>products as we move forward. 
>
>If you have any questions or if I may be of any further assistance,
>please do not hesitate to contact me.
>
>Best Regards,
>
>John Berdner
>
>SMA America, Inc.
>12438-C Loma Rica Road
>Grass Valley, CA  95945
>530.273.4595 - Tel
>530.274.7271 - Fax
>
>
>
>-----Original Message-----
>From: Jeff Oldham [mailto:starpower4u at juno.com]
>Sent: Thursday, April 24, 2003 04:18 PM
>To: RE-wrenches at topica.com
>Subject: Re: Sunny Boy Stats "final" [RE-wrenches]
>
>
>Jeff,
>
>I counted every call back, DOA and reship. In other words "failures", it
>does not matter how small or trivial to me, if I'm going back to the job
>to deal with it and it was not caused by UPS, the client or acts of the
>Goddess then it is an equipment failure. I would consider a broken LED a
>failure unless it fixed itself! Even if the number is half of what this
>group came up with it is still too high in my book and triple that of
>the company line. I was really just trying to see if our experience was
>unique or not, it turns out it is not.
>
>-jeff
>
>
>From the Solar, Wind and Hydro powered office of Jeff Oldham
>
>
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-- 
~~~~~~~~~~~~~
Jeff Clearwater
Village Power Design Associates
Sustainable Energy & Water Solutions for Home & Village

877-SOLARVillage
PO Box 764
Boonville, CA 95415

61 Baker Rd
Shutesbury, MA 01072
413-256-6777, 413-825-0372 (Fax)
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