[RE-wrenches] AFCI tripping on SB 4000US-12

[don energysolarnow.com]

You should also check the AC wiring. AFCI is detected as radio frequency noise from some kind of arc fault. It can be either AC or DC arcing.
I had some AFCI tripping issues that turned out to be loose wiring at the AC connector inside the SunnyBoy. It was easily fixed by tightening the screws. Since this connector is much closer than the DC wiring it would take less faulting to set off the alarm.

Don Barch
Energy Solar

>Friends:
>
> We installed a bunch of Shell SQ-150-PC modules on a ground mount almost
> 20 years ago.  The original SB2500 inverters died so we upgraded to
> SB4000US-21 inverters.  We had some ground fault or AFCI issues a number of
> years ago so we replaced all homeruns with PV wire which resolved the
> problem.
>
> These panels have J-boxes which we interconnected with 1/2? NMLT.  The
> home runs are with PV wire with absolutely no splices and the inter-panel
> jumpers are THWN.
>
> Recently we started getting AFCI disturbances on one inverter.  We
> isolated the fault to one string.  We opened every pull box and panel J-box
> and all of the wiring looks dry, clean and tightly connected.  We inspected
> every panel front and back and see no hotspots or visible corrosion.
>
> I have a megger I have never used.  The homerun is kind of long so maybe
> it has insulation problems.  I could isolate the homerun and megger those
> leads.  I am researching if I can megger PV modules.  It looks like this is
> commonly done.  That looks like my next step.
>
> Does anyone have any ideas on what I should do next? I suppose I could
> start swapping each of the 10 modules in the problem string with panels in
> the non-problem strings, but that seems like a lot of work.
>
> Thanks in advance.
>
> William Miller
>
> Miller Solar
>
> 17395 Oak Road, Atascadero, CA 93422
>
> 805-438-5600
>
> www.millersolar.com<http://www.millersolar.com>
>
> CA Lic. 773985

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