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

[Mark Frye]

Mick,

As time has passed I have lost track of my copy of the SMA white paper
regarding string fusing. As I recall though, if you subscribe to their
thinking (which I do), you don't' need individual string fusing until the
series fuses rating of the panel becomes less than 1.56 * Isc * (the number
of strings - 1). This of course assumes that the string conductors are rate
for at least 1.56 * Isc.

MPF


-----Original Message-----
From: Mick Abraham [mailto:mick at abrahamsolar.com] 
Sent: Monday, February 04, 2008 7:51 AM
To: RE-wrenches at topica.com
Subject: M-C branch plugs: Legal? Safe? [RE-wrenches]


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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