Ground fault [RE-wrenches]

[matthew tritt]

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
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