[RE-wrenches] Troubleshooting Stumper - Homerun Interference in Conduit/Inverter Turning Off/On Rapidly

Matthew Sirum matthewsirum at gmail.com
Wed Sep 7 20:33:38 PDT 2016


Greetings Matt,

I like the troubleshooting thoughts others have given.  If all else
leaves you with the issue persisting I would also consider checking
for current on the grounding system and on bonded conductive
materials/items on the property.  It may be helpful to see if there is
any current on the Equipment Grounding Conductors, Grounding Electrode
Conductor(s), metallic conduits & raceways, PV mounting system, and
etc.  If the inverter in this system has an AC Neutral connection
intended only for instrumentation and L1 & L2 voltage reference it
would be interesting to measure the actual current on it.  It is good
you have a similar system installed next door, you may need to compare
test measurements and readings.  If you run out of tests and
troubleshooting ideas it may be helpful to open (turn off) all the
circuits in the house/on the service and see how the PV system
performs while being the only item connected to the service.

The "smart" modules/optimizers may be making system troubleshooting
more challenging.  I wonder what Trina & Tigo has/can offer(ed) to
assist with troubleshooting?... and if there is an approved/safe
megger (insulation resistance) test for these modules?  This is an
interesting case.  I'll be continuing to follow the thread.  I hope we
can all learn something from this.

Best regards,

----MATT

Matthew Sirum
P.O. Box 1227
Greenfield, MA 01302-1227  USA
phone: +1.413.773.0611
email: MatthewSirum at gmail.com

Date: Wed, 7 Sep 2016 17:45:32 -0400
From: "Matt Partymiller" <matt at solar-energy-solutions.com>
To: re-wrenches at lists.re-wrenches.org
Subject: [RE-wrenches] Troubleshooting Stumper - Homerun Interference
in Conduit/Inverter Turning Off/On Rapidly

Wrenches,

One of our systems is having an issue I have not encountered before
where the inverter switches between nighttime mode and interconnection
every few seconds.  I am hoping for some technical wisdom from the
community.

We have an array of 20 TrinaSmart modules in two strings of 10.  The
array is connected to a Solectria 3.8 kW inverter.  The conduit run is
simple, all four homerun wires (#10 PVwire) in 1" EMT down to the
proximity of the Solectria inverter where the conduit switches to 1"
LFMC before entering the inverter.  The run is about 20', straight
down the side of the wall before hitting the inverter.  A 600V
jacketed communications wire was also in the conduit but has since
been removed and run separately.

Our inverter is starting up, running for a few seconds, giving a low
voltage error, briefly showing nighttime mode, then going into startup
mode again.  Solectria was gracious enough to send us a new inverter
but we have the exact same issue.  They tell us their error codes
(266, 274) indicate 0 volts.  The transition between low voltage error
and startup is almost instant.  Basically we have 20 seconds of start
up, 5 seconds of run, 5 seconds of error then repeat.  This is not a
grid problem, the identical system next door works fine.

In the process of troubleshooting, our technician pulled all four homerun
wires out of our conduit and meggered them.  They all tested fine so he
connected to the inverter.  The inverter worked fine.  The technician
verified grounding of the array and conduit, pulled new homeruns back
through the conduit, and reconnected to the inverter.  He had the same
error as before.

He connected each string separately to the inverter by removing the
string fuses.  Either string will operate fine independently.  With
string one in conduit and either homerun of string two in conduit (but
not both) the inverter operates fine.  With string two in conduit but
string one outside of conduit, the inverter does not operate.

I was certain the error had something to do with homerun roof wiring so I
went out with the technician and removed and checked pretty much every
module.  Everything appears fine, all connections solid, all homeruns
have been remade at least once at this point.  Now I am stumped and
lack the technical knowledge to diagnose the problem.  I would be
extremely grateful if an esteemed wrench can provide technical
support/advice.

Thanks,

Matt

Matthew Partymiller
Solar Energy Solutions LLC
(877) 312-7456
matt at solar-energy-solutions.com



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