[RE-wrenches] SMA Arc-Fault

[August Goers]

Dave,



It is particularly interesting that you have two inverters with
intermittent arc faults. I’ve been following this thread, and agree that
looking for noise on the AC side makes sense. Definitely update firmware
too!



That said, I thought I’d share a recent arc-fault story to this list. We
had a very persistent arc fault occur about a year ago. We replaced the
inverter, checked all DC-side wiring over and over, and could not find
anything. The arc fault intermittently persisted. The client had a big
fountain pump so we thought maybe that was the culprit. After a couple of
months of troubleshooting we disabled arc fault detection and everything
ran fine for about a year or so. Then, the client called us up and decided
to expand his system. We added a few panels to the roof and rewired all the
DC strings. During this process one of our installers found a melted MC4
connector:



https://goo.gl/photos/SR2ApXmoPcRcLZQu8



So, it turns out that we had a real arc fault after all! We had checked the
MC4 connections over a year ago and did not find this connector assembly
issue – apparently the terminal wasn’t fully seated into the connector. In
all fairness, it would not be easy to see whether the connector was seated
properly if the arcing wasn’t bad enough to show signs of wear. We are
giving our crews regular safety talks and training on all sorts of splices
and proper MC4 assembly methods to avoid arc-faults and loose connection
issues. It takes a lot of persistence.



August



*From:* RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On
Behalf Of *Dave Tedeyan
*Sent:* Thursday, November 10, 2016 10:14 AM
*To:* RE-wrenches
*Subject:* [RE-wrenches] SMA Arc-Fault



Hi All,



Maybe someone will have some ideas for why a couple inverters keep arc
faulting:



-There are two SB7000TL-22 inverters, Sunpower branded.

-3 Strings of 7 SPR-327's to each inverter. Kept separate until the
inverter.

-Ground mount about 50' from the shed where the inverters are located
(indoors)

-Simple grid connected system, no batteries.

-There is a whole house generator co-located in the shed.

-We interconnect by using piercing taps on the line side of the generator
transfer switch

-There has been only one power outage there since the system was installed
in April, but the generator fires up weekly.



-The arc faults have been happening on both inverters. Sometimes only one
at a time, sometimes both will go within a day of each other.

-The events have been approximately one a month, but sometimes more,
sometimes less.



-We have already checked every single connection in the system twice, by
two different people.

-We have replaced the underground wires (and they looked just fine)

-We have replaced all home runs.

-We have replaced both inverters.

-Arc faults are still happening.

-Arc faults are not always on the same day/time of the week.



I am wondering if this can be caused by the generator?

Has anyone run into a situation like this or something similar?



Thanks for your help,

Dave



*--*



*Dave Tedeyan*

*Project Engineer*



*Taitem Engineering, PC*

109 S. Albany Street, Ithaca, NY 14850

Voice: (607) 277-1118 x121

www.taitem.com
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