[RE-wrenches] Inverter Output Circuit OCPD Meltdown
Ray
ray at solarray.com
Thu Jan 23 16:53:29 EST 2020
We use this 3M wire numbering dispenser. They don't stick as well as
I'd like, but it can solve some very weird problems later.
3M STD Wire Marker Dispenser with #0-9 H-5223 - Uline
I'm also a fiend for color coding, and have had numerous discussion here
on the list about the need to color code wire. Crossed wiring as Jason
has illustrated to us, can be very dangerous and lead to issues none of
us could have predicted. Once again, this situation would have easily
been prevented by good old labeling and color coding by the original
installer Every time I open a box and see unmarked black wires running
every where, or inconsistent colors, I know the entire installation is
suspect.
Ray Walters
Remote Solar
303 505-8760
On 1/23/20 2:28 PM, Jason Szumlanski wrote:
> What made this installation (again, by others) a bit more complicated
> was that all branch circuit line conductors were black. I make it a
> point on my installations to require black for L1 and red for L2 up to
> #6 wire size. It's not a failsafe by any means but does reduce risk.
>
> *
>
> *
>
>
> On Thu, Jan 23, 2020 at 2:41 PM August Goers <august at luminalt.com
> <mailto:august at luminalt.com>> wrote:
>
> Jason -
>
> Thanks for sharing - this is a good lesson for all Wrenches. Years
> ago we had a dual string inverter installation where the DC
> positives and negatives were mixed between the two interters.
> String 1 positive went to inverter 1, string 1 negative went to
> inverter 2 and vice versa. The inverters tested out and ran for
> about two weeks and then one of them literally caught on fire.
> Since then, we implemented a policy of checking wiring coming from
> the roof down individually. In the case of microinverter branch
> circuits, this means checking each branch circuit voltage on the
> roof with the other breakers off one branch at a time.
>
> Not to get too far off on a tangent, but as we're installing more
> and more energy storage with lots of onsite wiring work, it is
> clear that fully testing wiring is of utmost importance. We have a
> procedure for checking voltage at each piece of equipment (such as
> a backup loads panel, etc) prior to turning on branch breakers.
> We've run into a couple of scenarios where hots and neutrals were
> mixed up causing 240 v to go to a 120 v circuit. Not good.
>
> August
>
> On Wed, Jan 22, 2020 at 2:58 PM Jason Szumlanski
> <jason at floridasolardesigngroup.com
> <mailto:jason at floridasolardesigngroup.com>> wrote:
>
> I discovered the issue I believe, so I thought I'd update all
> of you who gave me ideas on what to look for (thank you).
>
> And this is something that I stress the importance of all the
> time...
>
> The branch circuit pairs were not properly paired up! All of
> the L1 conductors went to L1 on the bus and all of the L2 to
> L2. However, for example, circuit 1 L1 and circuit 2 L2 were
> on a single 2-pole breaker. And circuit 2 L1 and circuit 1 L2
> were on another breaker. Everything worked because it was
> electrically connected to the right bus bar. However, when
> there was a previous fault one of the breakers probably didn't
> trip when it should have as a result of the improper pairings.
> It was reset a few times and just kept heating up and heating up.
>
> This isn't conclusive, but it sure makes sense. It wasn't fun
> tracking this down with 5 strings and 5 junction boxes on the
> roof, but once we started continuity testing and finding
> strange results, it became clear.
>
> Jason Szumlanski
>
>
>
> On Tue, Jan 21, 2020 at 12:10 PM Jason Szumlanski
> <jason at floridasolardesigngroup.com
> <mailto:jason at floridasolardesigngroup.com>> wrote:
>
> (System installed by another contractor...)
>
> I have been tasked with assisting in the investigation of
> damage in a subpanel used to combine inverter output
> circuits (5 strings of microinverters). There appears to
> be no damage to conductors or other system components. It
> looks like the damage started at the stabs of the bus bar
> where the breakers connect. Picture attached. Here are a
> few clues:
>
> * Monitoring indicates that damage occurred overnight a
> few weeks ago. That night we had rain as a winter
> front came through Florida, possibly lightning. The
> prior day everything was fine.
> * The next morning, only 2 of 5 strings started
> producing power, but 4 of 5 strings were reporting
> data to the Envoy. The two strings that were reporting
> but not producing power reported 0Vac and Voc on the
> DC side of the microinverters.
> * A couple of weeks later, 1 of the 2 strings that was
> producing power quit doing so, but continued reporting
> data.
> * Customer discovered damage yesterday.
> * About a week before the initial damage apparently
> manifested itself, another contractor installed a
> whole house generator transfer switch on the line side
> of the PV interconnection. The generator has never
> been run (there is not even a LP fuel source on site
> yet). I pointed out that the solar interconnection,
> which was previously on the supply side, would need to
> be moved to the supply side of the generator transfer
> switch's main breaker before operation. During the
> transfer switch installation, the contractor also
> switched line 1 and line 2, but that shouldn't
> really matter, except for Enphase consumption
> monitoring, which was messed up by the swapping of the
> lines.
>
> So I'm looking for ideas. I'm wondering if the OCPD would
> be a likely place for lightning damage to manifest itself.
> I can't visually detect any other damage anywhere else. I
> can't imagine that the transfer switch installation would
> have anything to do with it, but the timing is
> interesting. Other than replacing the subpanel and OCPD
> and firing it back up (no pun intended), I'm not sure how
> to approach further investigation.
>
> Jason Szumlanski
> Florida Solar Design Group
>
> *
>
> *
>
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