Beachless

I'm really not sure but I'm going with a bad breaker. It burned holes on either side of the breaker melting to the one next door. The fuses are in line on positive and negative from the panels so there should be no way more than 20a flowed through the breaker from the panels. I don't believe power can flow from the MPPT through a fused breaker back to the MPPT without there being damage somewhere either.

That made in China sticker frequently lives up to its name. Its really hard to trust any of it.

Thanks Coulomb. I recently bought the complete wired combiner box so its all new and the breaker is rated 63A, 600v DC no polarity indicated anywhere on the breaker. The MC4 connectors were just used as they came already wired into the combiner box but I'm glad they were there as that was the only way to disconnect things. The good news after inspecting things early this morning and switching in a spare DC breaker everything is working as it should. The MC4 looks good I hit the power button on the inverter somewhere in the chaos and I think either the melted breaker or switching off the inverted dropped the current so the connector wasn't under much load. Why the breaker self combusted with less than 11A load I don't know but I'm just glad its the only thing that seems to have been damaged.

So I made a booboo and reversed the polarity on the MPPT PV input, the DC breaker melted instantly and released a bunch of smoke and it took me a while to unplug a MC4 in the chaos. The 20A fuses are all fine by the looks of it and didn't blow so the 63A Breaker doesn't inspire much confidence. I even checked everything with the multimeter before plugging in to make sure voltages are what they should be etc but alas. The manual talks about the battery not having reverse polarity protection but what about the MPPT? I dont want to do more damage so interested if someone knows? I measured the resistance on the MPPT's one being +-0.7M Ohm and two +- 1.4M Ohm but I am not sure what they are normally but hoping that means they are still OK.

I'm busy gathering all the equipment for my solar install but I'm still looking for a battery cabinet that will hold up to 3 5kwh batteries (12u). I see some server racks for cheap but I'm not sure if they will hold the weight. Any leads to a good rack that won't break the bank?

Thank you for the elaboration.

@Sc00bs thanks for adding that to this interesting thread. Do you mind elaborating a bit on the non essentials bit? Can those items still be powered from PV or is it just pass through? Edit: seems I just need to read "Weller" my question was answered thanks.