[RE-wrenches] Inverter Output Circuit OCPD Meltdown

[Ray]

Almost every meltdown I've looked at was not due to lightning, but heat 
from a high resistance connection.  A lug not torqued can cause 
surrounding plastic to melt.  If the wrong breakers are used with the 
buss bar, they might snap on and work, but not be able to take the 
current over time.  Coupled with high humidity, you can start getting 
corrosion going which further increases the resistance.  Eventually, if 
its gets bad enough, the resistance can cause glowing red hot metal, and 
attached insulator plastic starts melting.

Its also possible that someone knocked a wire or breaker loose? Or 
possibly shorted the buss doing something wrong, corrected the error, 
but didn't realize the buss had been damaged.    Lots of guessing, but 
that's how you figure it out.

If it was lightning, there would be lots of related damage: Enphase 
inverters and other electronics cooked.

Ray Walters
Remote Solar
303 505-8760

On 1/21/20 12:51 PM, Jerry Shafer wrote:
> Wrenches
> Cant tell anymore but l had a buss failure due to water getting on 
> buss and pealing the tin off the buss and the aluminum base will light 
> up real quick.
> Jerry
>
> On Tue, Jan 21, 2020, 9:10 AM 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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