Ground faults / NEC changes for 2005 [RE-wrenches]

[jberdner at sma-america.com]

Wrenches:

Fuses or breakers can be used in both battery conductors if the system
is not grounded.
Then Code says over current protection must be used in all ungrounded
conductors. This means you would have  over current protection in all
current carrying conductors.
Today the Code says we can not use breakers, fuses, or switches in the
grounded conductor so ground faults are a real hazard.

There is some language about this in the proposed NEC changes for 2005.
An ungrounded the system does add some costs for OC protection but it
allows us to use other power conversion topologies that are safer, lower
cost, and higher performance.

If you can find a few minutes please review the proposed changes for the
2005 code and forward letters of support for ungrounded systems to Ward
Bower at Sandia.

If you have any questions, or if I can be of any further assistance,
please do not hesitate to contact me.

Best Regards,

John Berdner

SMA America, Inc.
12438 Loma Rica Drive, Unit C
Grass Valley, CA  95945
530.273.4595 (voice)
530.274.7271 (fax) 


-----Original Message-----
From: matthew tritt [mailto:solarone at charter.net] 
Sent: Thursday, November 14, 2002 8:27 PM
To: RE-wrenches at topica.com
Subject: Re: Ground fault [RE-wrenches]

WM

Wouldn't the protection of + and - circuits by breakers  and/or fuses
prevent this sort of problem? Why shouldn't both be protected in a
battery-based system?
Matt                                                      Original
Message -----
From: "William Miller" <wrmiller at slonet.org>
To: <RE-wrenches at topica.com>
Sent: Thursday, November 14, 2002 11:48 AM
Subject: RE: Ground fault [RE-wrenches]


> Kurt:
>
> There was a 60 amp DC rated circuit breaker on both sides of the
charge
> controller.  Curiously, when I arrived on site, all circuit breakers
had
> been opened by the client, AC, DC, etc.  Even then, when I touched the
> burned circuit board with a screw driver, it arced and sparked enough
to
> scare us.  Note in theory B no current flows through the positive leg
of
> the CC.  Breakers do no good there.
>
> WM
>
>
> At 09:54 AM 11/14/02 -0600, you wrote:
> >Greetings William,
> >
> >There must have been a lot of current going though that CC.  I didn't
> >know the RV products would allow reverse current flow.  Wasn't there
a
> >fuse or DC rated breaker between the CC and the battery?  I usually
> >place one both between the battery and the CC and between the CC and
the
> >array.  It seems to me such over current protection would have
prevented
> >this almost as well as a GFI.
> >
> >Kurt Nelson
> >SOLutions
> >
>
> __________________________________________________________________
> 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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