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

[August Goers]

Hi William - Is this a TL-21 inverter
<https://files.sma.de/downloads/SB3-5TL-21-IS-xx-14.pdf?_ga=2.101814081.1325009506.1687199204-2010138759.1678983058>
line from maybe 8 or 10 years ago? If I recall correctly, that was around
the time period that SMA was first shipping with AFCI detection - we had a
few SMA inverters from that vintage producing false AFCI errors. I think
that long home runs can be part of the issue and the inverter circuitry was
a little too sensitive. You might try calling SMA to see if there is a
firmware update or a way to disable AFCI if you feel comfortable
with disabling that safety feature. Separately, we've had a few
phantom type AFCI errors on older modules and after tons of troubleshooting
we think that it might have been internal to the modules themselves.

Good luck!

Best, August


On Mon, Jun 19, 2023 at 11:11 AM William Miller via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> 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
>
> CA Lic. 773985
>
>
>
>
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