[RE-wrenches] Outback radian inverter with FM 100 ground fault

[Mac Lewis]

Hello Dana,

Ground faults are tricky.  Here is how I would tackle this on a sunny day:
1.  Visual inspection of array, looking for backsheet, wire damage, broken
glass, critter stuff (nests and bite marks).  Look for water intrusion or
evidence that water has been somewhere that it shouldn't.
2.  Visual inspection of all splice boxes, checking for wire insulation
damage, evidence of water intrusion and critter entry.
3.  Probe voltage between +, - and Ground (do this at a string level
initially, and isolate strings and do this at open circuit).  Any evidence
of bouncing voltage readings, loss of voltage, not rock solid voltage
suggests you may have a ground fault in that string.  If its in the string
somewhere, you may see the voltage bounce and read in some fraction of the
string voltage.  This can tell you where in the string it may be.  FOr
example, if you have a 5 module string, you may get a 3/5 voltage reading
if the fault is near the 3rd module.
4.  Turn off array at combiner and run continuity tests between +, - and
Ground again (no gfp fuse).  If you have continuity, this may suggest a
ground fault in conduit run between combiner and FM100.

Good Luck, bring extra fuses!

On Sun, Jan 19, 2025 at 7:07 AM Dana Orzel via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Yes I have 2 FM100s
> Dana Orzel
> C: 208.721.7003
> E- dana at solarwork.com
>
> On Jan 18, 2025, at 7:08 PM, Kirpal Khalsa via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
> 
> Dana...
> Do you have multiple FM 100s? If so only one should have the GFI fuse.
> Broken panel with water getting into glass?
> Turn it off and wait 5 min and turn it on.  Usually clears it especially
> if it's a faulty nuisance trip.
> Have had numerous FM 100s give faulty afci errors.  Removing the.afci
> boards always resolved this issue.  But of course check all you connections
> leading to and from the cc.
> Keep a few extra 1A gfi fuses handy....you may need a couple to test it
> all out.
> Keep us posted.
> Good luck
> Kirpal
>
>
> On Sat, Jan 18, 2025, 2:40 PM Dana Orzel via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> Hey, all you wise ones,
>> 37 years in the business and I’ve never had a ground fault ever in any
>> installation I’ve done or my home systems. I went out to my system here an
>> hour ago and one FM 100 is completely turned off claiming ground fault on
>> the mate 3S.
>> I guess my first question is :
>>
>> Is this really a ground fault ?
>>
>> I had removed the ground fault breaker when I upgraded due to space
>> considerations
>>
>> In my entire time in this business, I’ve never had to deal with the
>> ground fault any suggestions on how I should be tracing this?
>>
>> Has anybody seen this in an FM 100 when it wasn’t a ground fault?
>>
>> I do own a megger&  I’ve never had to use it. I only bought it about
>> three months ago cause it seemed like a good idea and I might need to use
>> one someday, Maybe I’m psychic ?
>> now if I could just figure out how to trace this out.
>> All suggestions welcome thanks all!
>>
>> Dana Orzel
>> C: 208.721.7003
>> E- dana at solarwork.com
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-- 



Mac Lewis

*"Yo solo sé que no sé nada." -Sócrates*
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