PV combiner box protection [RE-wrenches]

[Ray Walters]

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Hi Phil;

A dead short doesn't always happen. Many times the wire is pinched and the 
short can be less than 20 amps, but more than the cord rating. I have 
actually seen burned lamp cord that didn't trip the breaker. Actually take 
a survey, but I would say the majority of lamp cord, christmas lights, etc, 
that had a short were not full over 20 amp type short circuits. They were 
worn insulation with a few copper hairs touching type of connections.
As far as daisy chaining 6 modules,  I agree  that's a problem. I've seen a 
few where that last module jbox  was deformed from the heat. I'm just 
saying I think a good balance between safety and cost would allow some 
careful paralleling of PV circuits. Come on, you're really going to bring 
each 50 watt module in a 12 volt system in on a separate wire and breaker?

Ray




>Ray,
>
>I understand your reasoning on this, and can agree  with you to a point.
>the device does fail, and if it does fail in a short, a LOT more than 20



>I just received a photo of a j-box where 6 modules were daisy chained, and
>the last module in the row smoked its terminal strip.  By my calculations,
>it was subjected to 27 amps of current flow at 12v.  I have come to believe
>
>Phil Undercuffler ext.238
>Technical Support
>phil at dankoffsolar.com

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