[RE-wrenches] Sol-Ark 15K AC Coupling

[Jason Szumlanski]

Hi all,

Over the last three days I have had one of this infuriating and frustrating
experiences with Sol-Ark where you talk to 3 people and get 10 different
answers. At least I think I finally got the right one today. Here is the
scenario and problem I was experiencing:

At a (very) remote location that is a boat ride away, I have three 15K
inverters paralleled in a 120/240V system, off-grid, generator connected to
the grid input (but not being used). The PV array connected to the DC
inputs totals 40kW split across the three inverters. There is a 9.7kW
Enphase system (8.4kW AC inverter rating) connected on the load side of the
inverter outputs. Massive battery - 110kWh. Everything has been working
well for a couple of weeks since we got it set up.

Then, over the last three days, we began experiencing unexpected shutdowns
where the inverter would repeatedly stop inverting and PV would stop
charging. There was usually no indication of errors on the screen.
Everything was just stopped, but the inverters remained on. Sometimes they
would restart once, only to shut down again relatively quickly. We had to
manually restart the inverters with the ON/OFF buttons. Then we started
getting various errors, with F50 being the strange one that is not
documented. I reached Sol-Ark, and they said the F50 points to an AC input
issue, but the generator was not on, so that didn't make sense. I was on my
own to double-check all of the wiring.

But there was also an F41 Parallel System Stop error, which pointed me to
that suggested cause. I realized that one of the inverters had a -1725 COMM
firmware, whereas the others had -1726. I don't know how that happened
because I'm certain that I had them all on the same firmware at one time.
Anyway, I spent all day yesterday trying to reach Sol-Ark and getting the
firmware to match. I thought we had the issue resolved by the time I
left, as I was able to run the system for an hour without a shutdown.

Then I got a call at noon today from the owner. Same problem. System shut
down.

I was able to reach Sol-Ark immediately this time and the agent gave me a
more plausible answer. He said the F50 error points to something wrong with
the AC coupling. We started to put our heads together and I realized that
this issue first popped up around mid-day on Thursday, and then repeated
itself mid-day on Friday. Here we are again today, and I get the call at
noon. It seems like the issue happens as soon as the batteries reach 100%
capacity. It's like the Sol-Ark is not commanding the IQ8A microinverters
to shut down. I had the owner shut off the AC coupling input breaker and I
remotely unchecked the box for AC coupling on the load side. That seems to
have resolved the issue.

Ok, fine, but how do we resolve this (I asked Sol-Ark)? The "solution" I
was offered is to move the AC coupled input to the GEN terminals. The
problem is that I need to reserve the GEN terminals for an upcoming Smart
Load subpanel. That's why I installed the AC coupling on the load side,
which is a documented and accepted practice.

I do have AC coupling working without issue on a grid-tied system at
another location with dual Sol-Arks, but that is connected to the GEN
terminals. This is the first time I have AC coupled on the load side. Has
anyone successfully AC coupled on the load side, particularly with
microinverters?

I'm probably going to have to climb the customer service ladder at Sol-Ark
to get a resolution for this, but I wanted to get some feedback in case
someone has already been down this road.

Thanks in advance,

Jason Szumlanski
Florida Solar Design Group
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