[RE-wrenches] Finding ground faults

[Kent Osterberg]

Steve,

It would be appropriate for the GFDI to have 80-amp rated contacts that 
do not have an over-current trip mechanism. IMHO, the fact that they can 
trip on over-current and unnecessarily interrupt the dc system bond is a 
serious design flaw.

Kent Osterberg
Blue Mountain Solar, Inc.
www.bluemountainsolar.com


On 5/23/2012 9:27 AM, Steve Higgins wrote:
> Bob,
> Be careful with that GFDI... It's most likely wired on the output of 
> the controllers, on the battery side.
> This can trip if a ground fault is occurring, or if you are exceeding 
> 80 amps of current.   With 8, 3 module strings, an edge of cloud event 
> you could have the 80amp portion of that breaker tripping rather than 
> the GFDI.
> Steve Higgins
> Sales Application Engineering Mgr
> Direct 360-618-4313
> Outback Power Technologies
> 5917 195th Street NE Arlington, Washington 98223
>
> ------------------------------------------------------------------------
> *From:* re-wrenches-bounces at lists.re-wrenches.org 
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Bob 
> Clark
> *Sent:* Tuesday, May 22, 2012 7:37 PM
> *To:* re-wrenches at lists.re-wrenches.org
> *Subject:* [RE-wrenches] Finding ground faults
>
> 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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