[RE-wrenches] Finding ground faults

[boB at midnitesolar.com]

Hey Bob !  Hi from the west side of the hill.

This seems like an easy one...  Well, maybe...

One a dry day, take a garden hose and spray different parts of the 
system and see if you can
duplicate the problem and locate where the water makes it trip.

But you may have to wait a while for each spot sprayed to let it fault 
out before spraying
another spot.  That's  how I'd start out.

This also seems kind of weird in a way because of the current necessary 
for that breaker
to trip.  What ?  1/2 amp or 1.0 amp or so....  That's not a real small 
amount for rain.
I bet something is rusty or corroded or something like that.  Please let 
us know what
you find !!

boB




On 5/22/2012 7:36 PM, Bob Clark wrote:
>
> Wrenches:
>
> Sorry to bring up this situation again, but I could not find a 
> previous discussion thread that talked about step-by-step procedures 
> for tracking down ground faults (I believe it was John Berdner who 
> provided the bulk of the writing in that regard and it related to high 
> voltage strings---not that 75-85 volts per string is all that low).
>
> We have an Outback FLEXpower Two system with 8, 3-module strings 
> (Silicon Energy 190W, 25.3Vmp, 7.5 Imp) combined in a Midnite Solar 
> MNPV12 combiner with breakers.  The cables from the array are routed 
> to two different Wiley 4-string pass-through boxes (located under the 
> two center strings) and then off of the roof and into the PV combiner.
>
> Up until this week the system has seen several weeks of awesome power 
> production.  Yesterday, the rains came and the GFDI breaker tripped.  
> Every time it rains, the little green breaker on the GFDI trips off. 
>  That tells me that the ground fault is occurring in a place where at 
> least one of the conductors on one of the strings (possibly more) is 
> getting wet and conducting current to ground.
>
> It would seem to me that the most likely place for moisture to cause a 
> ground fault to occur in this system would be in the pass-through 
> boxes.  This would mean removing the central modules to access the 
> pass-through boxes.
>
> Any of you who have mounted the Silicon Energy modules know that the 
> cables are contained in trays along the side of the modules until they 
> are routed through conduit to the pass-through boxes.  So, if there is 
> current going to ground from any of these cables, it could even be 
> occurring in any of the 9 trays along side of the modules.  I do not 
> like the idea of tracking down a ground fault in one of these trays as 
> they are all interconnected.
>
> How best (and safely) to track down where the ground fault is 
> occurring?  Any advice as to the best and safest way to track down the 
> ground fault(s) would be greatly appreciated.
>
> *Bob Clark*
>
> */SolarWind Energy Systems, LLC/*
>
>
>

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