Yes this is an interesting case, as are the debug suggestions given. The wire pairs working out of metal conduit point strongly at either ground faulting or inductive coupling. You seem to have eliminated the obvious wiring issues like polarity and grounding. Since you have a working system next door and you are already putting in the
hard work of swapping inverters and wires, it is worth trying to
swap the inverter from that working system with the non-working one.
This would either indict or eliminate the inverter as the culprit.
It is worth noting that the TrinaSmart modules with Tigo Maximizers are quite capable of being the source of the problem. They attempt to do MPPT at the module level, and can conflict with the inverter's attempts at MPPT. We have had problems with other inverter brands to the extent that power production was impaired, although not as bad as your complete shutdown. It was necessary to use the inverter setup options to shut off MPPT. If Solectria allows this it is worth trying.
Also I have had problems with Tigo Maximizers on mismatched strings shutting down one string completely to "maximize" others. You may be seeing the effect of communication problems from the maximizer wireless controller. Try disabling them if possible by shutting down their controller with its secret software.
I'm guessing that plain dumb modules with a plain dumb inverter would not be suffering this shutdown problem. Something in your system is too smart for your own good.
Don Barch
Energy Solar
-------- Original Message --------
-----Original Message-----
From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On
Behalf Of Matt Partymiller
Sent: Wednesday, September 07, 2016 4:46 PM
To: re-wrenches@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
m...@solar-energy-solutions.com
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