module connection arrangement [RE-wrenches]

[jberdner at sma-america.com]

Todd:

The series fuse is there primarily to protect the module against back
feed current during a fault (UL requirement).  For example if you have a
short (to ground) in a series connector then you can get big currents
flowing from other parallel strings of modules. You can use the fuse for
over current protection of the wiring but that is not UL's main reason
for it. 

This brings up an interesting question if the fuse is in the Jbox.
The wiring between the parallel connection point and the fuse is
unprotected. This could create a hazard if there was a fault between the
parallel connection point and the fuse. Depending on the number of
parallel strings and the size of the wire I think you might need
additional over current protection to protect the wire.  Since this is
probably impractical this would argue against fuses in the module jbox.
There may also be some code accessibility issues with fuses in the jbox.


Comments from Wrenches ??

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

Best Regards,

John Berdner
Phone: 530.273.4595
Fax: 530.274.7271


-----Original Message-----
From: Todd Cory, Mt. Shasta Energy Services [mailto:toddcory at jps.net] 
Sent: Tuesday, May 21, 2002 2:21 PM
To: RE-wrenches at topica.com
Subject: Re: module connection arrangement [RE-wrenches]

While series fuses in the panel junction boxes sounds like a good idea,
it will
not protect the conductor between the battery/parallel string connection
and the
panel. I thought that was the whole point of series fusing, to protect
the wire
feeding from the PV's.

Todd


Drake Chamberlin wrote:

> With Siemens SP 75 modules, with their excellent junction boxes and 15
amp
> series fuse rating, I think we can safely use a 15 amp series fuse on
each
> string, in the j box, without concern.

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