Any further investigation into the hardware differences between the newer
15k and the original 15k I mentioned before? That was the only thing that
fixed the issue for us. We had to insist they replaced it with a newer
matching inverter. I should have made note of the serial numbers to try to
narrow down the time frame when they changed the design. The newer design
has a small circuit board bolted to the bottom of the enclosure that wasn't
present in the original..




On Sat, Nov 9, 2024, 7:16 AM Jason Szumlanski via RE-wrenches <
re-wrenches@lists.re-wrenches.org> wrote:

> I wrote in another thread about an off-grid quad Sol-Ark system that was
> shutting down due to parallel stop when one of the four inverters
> experienced a DC PV fault, and how that shutdown is far from ideal. The
> same system is down once again, this time due to an AC fault code.
>
> The homeowner started getting repeated F18 and F34 AC overcurrent faults
> on one of the slave inverters. This, in turn, shut the entire system down
> due to parallel stop faults (F41). None of the other units had AC
> overcurrent faults, and the load is nowhere near requiring all four
> inverters for even the most demanding circumstances. It was designed this
> way for redundancy, which I am quickly finding out is not Sol-Ark's strong
> suit.
>
> To diagnose the issue remotely, I had the owner turn off all four load
> breakers, all DC PV input, and the AC microinverter input on the GEN
> terminals. I had them restart everything (several times). Every time, the
> same inverter would have repeated AC overcurrent faults, and the others
> would have parallel system faults. Since there were no loads connected by
> virtue of the load breakers being open, I suspected this had to be an
> internal fault.
>
> I went to the site, and Sol-Ark Tier 1 tech support had me shut off all
> inverters and take the suspect inverter out of parallel operation mode. As
> a standalone master it was able to power up and support the entire house
> load without issue. Then we reprogrammed it for parallel operation again
> and turned everything back on. We were unable to stay on the phone long
> enough to determine if this was successful, but ultimately, the fault
> returned. I was told to call and ask for Tier 2 next time if it happened
> again, which I intend to do on Monday. At this point, the issue can only be
> internal to the unit, and I intend to demand warranty replacement of
> suspect components or the whole unit.
>
> I had to get the system running, so I wanted to take the bad inverter out
> of the parallel system. I was hoping that simply shutting it down would
> work. This is the third of 4 inverters in the Modbus chain. When turning it
> off completely (all AC and DC switches disconnected), the 4th inverter
> would fault, presumably because the Modbus signal was not being relayed,
> but inverters #1 and #2 worked fine. However, I wanted #4 to also continue
> working while taking #3 out of service. So then I turned on the battery
> disconnect for #3 but left it in the off mode by not pressing the on/off
> button, thinking that it would allow relay of the Modbus signal from #2 to
> #4. That allowed the system to work momentarily, but then everything
> faulted out due to parallel system stop. In other words, I was going to
> have to physically take #3 out of the Modbus daisy chain to make this work.
>
> Of course, I didn't have a long enough Cat5 cable with me, nor a Cat5
> splice connector. So I had to rig something, which I did successfully to
> jumper from #2 to #4. But when I turned everything back on, #4 still would
> not work. I eventually realized that you have to change the Modbus address
> from 04 to 03 in the settings. Apparently, the addresses need to be
> sequential for it to work. Once I did this, I was able to get the system up
> and running again as a triple-inverter parallel setup. No faults were
> observed. So the theory was proven that #3 has an issue internally.
>
>
> Anyway, bottom line, I am disappointed at how one inverter fault takes
> down the whole paralleled system, and also how taking a faulted inverter
> out of the system requires physical and programming changes. Turning it off
> should be sufficient. This is a very poor way to implement a parallel
> system that should provide the peace of mind that redundancy implies. Now I
> have a customer who thought they were getting a system with failsafe
> redundancy that actually requires a service call every time one of the
> paralleled units decides it does not want to play nicely with others.
>
> Jason Szumlanski
> Florida Solar Design Group
>
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