[Solved] My off-grid 12000XP 3-phase system had arc fault on non-connected MPPT, won&#039;t come out of standby

@eg4eric I got a support call this morning at 6:30am my time, they weren't able to diagnose online so I was supposed to get a call back at 9 but didn't. I'm going to be unreachable for the rest of the day, if there's some diagnostic I can perform here could you give me instructions to do so? I'm an engineer by training and know how to use a multimeter.

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gigadude

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February 3, 2026 2:15 am

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Hi Eric, yes it's online, I don't see warnings or errors other than the over-current warning in the log. 43730P0310 is the one that's stuck in standby, BGR is the station.

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EG4 Eric

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February 3, 2026 10:18 pm

@gigadude
Are these inverters wired to work in parallel? or are they separate systems?

gigadude

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February 4, 2026 5:32 am

@eg4eric they're wired as a 3-phase system, the inverter having problems is the master. I was out this afternoon and when I came back around 9pm my time my inverters were all in standby, was that something somebody at your end did? I was able to power-cycle them and get my power back on.

EG4 Eric

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February 6, 2026 6:50 pm

@gigadude
I put the inverters in parallel, and it seems to be pulling wattage from all 3 inverters.

I will put them back into single view, but if you want to see them in parallel, just hit the parallel button on the top left of the screen under SYSTEM INFORMATION

Can you share how the system is wired?

gigadude

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February 8, 2026 6:30 pm

@eg4eric it's wired as inverter #1 (the one having problems) to L1/L2, #2 to L3/L1, #3 to L2/L3, the 6 batteries are currently connected using the paralleling cables to form one big battery bank with inverter #1 as the master. I'm aware of the recommendation to use fuses & busbar for this configuration, I do plan to eventually do that. During daylight hours I see #1 "producing" 56W of power from the MPPT that isn't hooked up to anything, I see ~300V on the string that is hooked up but 0W. I don't see any power feeding from #1 into my panel, EPS is 0W on both legs.

It's not the most clear photo but it shows the conduit open, #1 is double-cabled to battery 1, #2 to battery 3, #3 to battery 5, there's a single cable pair between each battery:

If the FETs are blown in #1 is there a way to replace the circuit board(s) in question without tearing down the inverter and sending it in for repairs? I haven't opened the main enclosure to take a look due to the "invalidates warranty" stickers.

EG4 Eric

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February 13, 2026 3:07 pm

@gigadude
I would have to double check if we can send a replacement board or if the whole inverter would need to be replaced.

Have you tested voltage on the PV input?

Are all the PV Disconnects on, for each inverter (located on the side of the inverter)?

Also, are you able to share more pictures of the front of the inverters? If possible, also sharing the wiring diagram. I just want to make sure I have everything we need in case we need to replace it.

gigadude

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March 11, 2026 8:33 am

@eg4eric

Hi sorry it took a while to get the info, here's the wiring diagram

BGR_wiring_diagram.pdf

The SP ovals are Midnite Solar 600V DC surge suppressors, there are also 3 Midnight Solar AC surge suppressors wired at the main panel across the 3 phases. The Load legs are wired to a pair of 50A 3-phase breakers at the main panel. The main panel is bonded to an Ufer ground in the slab, all other equipment grounds are wired to the main panel. The yellow lightning bolt shows where the arc to ground happened, at that time there were no panels hooked up on the U inverter's MPPT #2 lugs, there was a string of 8 panels wired into the MPPT #1 lugs and the PV disconnect was on (connected).

Since the fault I've installed the remaining panels, all of the PV inputs are showing reasonable voltage during sunlight hours, when I try turning on the disconnect on the U inverter it shows 50W charging from MPPT #2 and 0W from MPPT #1. I'm leaving that inverter disconnected till this is resolved, the other two inverters seem to be operating normally and charging the batteries etc.

This post was modified 1 week ago 2 times by gigadude

gigadude

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March 13, 2026 4:18 pm

@eg4eric was the diagram sufficient? I need to get my bad inverter up and running again, I've been hitting overload shutdowns with my water heater due to colder temps requiring more power.

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gigadude

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March 15, 2026 8:31 am

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@eg4eric I think this topic was mistakenly marked "solved", I still need help getting my inverter fixed. Was the circuit diagram I sent sufficient or do you need more detail?

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EG4 Eric

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March 16, 2026 3:59 pm

@gigadude I am going to get with our team about this and show them the wiring diagram. I will let you know if we need anything else.

gigadude

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March 16, 2026 4:50 pm