Ground fault [RE-wrenches]

[William Miller]

Matt:

The client did not install a combiner.  Nonetheless, if there were a ground
fault after the combiner, the combiner fuses would not have helped.


William


At 09:50 AM 11/14/02 -0800, you wrote:
>I noticed that your drawing shows no series string protection.
>Theoretically, if there were fuses installed for the faulted string none of
>this would have occurred. Were there fused combiner boxes installed in this
>system?
>
>Matt
>----- Original Message -----
>From: "William Miller" <wrmiller at slonet.org>
>To: <RE-wrenches at topica.com>
>Sent: Thursday, November 14, 2002 2:30 AM
>Subject: Ground fault [RE-wrenches]
>
>
>> Colleagues:
>>
>> Over the last weekend I received a call from a client reporting that an RV
>> products SB50 that I installed for him had "burned up."   I went out first
>> thing Monday to look at it and almost pooped my pants. The unit had burnt
>> inside to a crisp and damn near sent his warehouse up in flames.  This was
>> some serious fire and it scared me.
>>
>> We have performed some analysis on what caused the problem and posted a
>> pretty comprehensive report on our web site (url in my signature lines
>> below.  Click on Case Studies.  The photos and diagrams are somewhat large
>> to show adequate detail, so download this when you have the time).
>>
>> Part of the problem may be that the client keeps adding legacy Cariso PV
>> modules.  He wants to increase his charging and may well have exceeded the
>> capability of the SB50.  One reason he adds modules is that he may not be
>> getting a realistic charge rate because the ground fault we discovered may
>> have been siphoning off amps for some time.  The problem may existed for
>> some time and came to a head when we finally received rain here after a
>> long dry summer.  The ground conductivity may have increased enough to
>> bring this problem to a critical point.
>>
>> The only reason the fire did not spread is that the client put a sheet
>> metal cover over the equipment to prevent water damage in the case of a
>> roof leak.
>>
>> I believe there are two lessons to be learned:  Ground fault breakers may
>> be more valuable than I could have imagined, and sheet metal backing is a
>> valuable addition to any installation.  These are both ideas discussed
>> here, and they may warrant further discussion.
>>
>> I was off the hook on this installation because the client wired his own
>> arrays.  Having said this, it would be very easy for anyone to create this
>> kind of fault.  Using tray cable, for example, one could easily pinch a
>> positive wire in a rack foot when lowering a rack.  All of this scares me
>> and makes me want to perform all of my installs like delicate surgery.
>>
>> Comments are appreciated. I especially want to hear if anyone agrees or
>> disagrees with the premise that a GFI would have prevented the failure.
>If
>> so, the point is not to require a GFI when the arrays are on the roof of a
>> dwelling, but when any of the circuitry is IN or runs through the
>dwelling.
>>
>> Thanks for reviewing this case and commenting.
>>
>> William Miller
>>
>> __________________________________________________________________
>> William Miller
>> Miller Power and Communications
>> PO Box 50, Santa Margarita, CA 93453
>> Voice :805-438-5600 Fax: 805-438-4607 VMail: 805-546-4875
>> email: wrmiller at slonet.org
>> http://millerpowerandcomm.com
>> License No. C-10-773985
>> _____________________________________________________________
>> Compatibility:
>> Word processor: WP7
>> Spreadsheet: Quatro Pro 7
>> CAD: Microstation 95, DXF, Visio 4.1T
>> _____________________________________________________________
>> "Every decent man is ashamed of the government he lives under."
>>                                     H. L. Mencken
>> __________________________________________________________________
>>
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>
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>

__________________________________________________________________
William Miller
Miller Power and Communications
PO Box 50, Santa Margarita, CA 93453
Voice :805-438-5600		Fax: 805-438-4607	VMail: 805-546-4875
email: wrmiller at slonet.org
http://millerpowerandcomm.com
License No. C-10-773985
_____________________________________________________________
Compatibility:
Word processor: WP7
Spreadsheet: Quatro Pro 7
CAD: Microstation 95, DXF, Visio 4.1T
_____________________________________________________________
"Every decent man is ashamed of the government he lives under."
                                    H. L. Mencken
__________________________________________________________________

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