M-C branch plugs: Legal? Safe? [RE-wrenches]

John Berdner jberdner at sma-america.com
Mon Feb 4 09:29:55 PST 2008


Mick / Wrenches:
 
The UL module guys once explained the fuse / no fuse issue in a way
thet really helped me.
Think of the string of modules as a piece of wire with an ampacity that
is set by the UL series fuse rating.
If you then fault that "wire" then there will be current flow from the
other strings wired in parallel with it.
You can then calculate the fault current at 1.25 Isc of the other
parallel strings.
If the result is more than the UL series fuse rating of the module then
you have a design problem (regardless of the wire size feeding the
strings). 
If it is a Code issue or not is still an open question since the Code
does not really address the issue of UL series fuse size being used as
an ampacity.  
Logically this interpretation makes sense but the Code does not
specifically address the issue of module "ampacity".
 
Best Regards,
 
John Berdner
 


>>> mick at abrahamsolar.com 2/4/2008 07:50:42 AM >>>

Hi, Wrenchers~

The Multi-Contact "branch connectors" connect two PV strings in
parallel 
by just plugging them together. MC part numbers for these "branch
plugs" 
would include PV-AZS3 & PV-AZB3.

These connectors have a UL recognition mark, but they seem non-code 
because there's no individual fusing for each string of modules.

Are code issues raised by this product? I'm working on something where

there are no codes, so my other question is: are safety issues raised?

Specifically, if one plug-parallels three Kyocera 135's (with, say, one

30 amp breaker to protect the trio from the 12v battery side), is that

hazardous? 30 amps exceeds the series fuse rating recommended for the 
KC-135 which again seems non-code. On the other hand, if one uses 10 
gauge plug leads (which are likely fine with 30 amp protection),
perhaps 
the worries are small. 

Multi-Contact rates the branch plugs for 30 amps when 10 gauge wire is

used. If they're non-code, however, who uses them, and how? 

Thanks all around,

Mick Abraham, Proprietor
www.abrahamsolar.com 




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