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
<[email protected]
<mailto:[email protected]>> 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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