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

[William Miller]

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Mark, Mick:

The SMA white paper on allowable string quantities is on my web site at 
this link:

http://mpandc.com/resources/resources.html

Note however, that the logic presented in this paper hinges on proof that 
the destination device for your PV (inverter, charge controller, battery 
bank or whatever is applicable) can not possibly contribute to short 
circuit current through the modules.  This is a key point.

William Miller

At 08:28 AM 2/4/2008, you wrote:

>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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