Burnt MC4 connector

Guys today my 2.5kw solar system all of a sudden cut out on a hot day while I was running a 2.0kw air conditioner.

I went to investigate and to my horror I found a MC4 connector completely melted through. Now to be honest I crimped these myself from connectors I got on Amazon for cheap. It’s also possible it got wet a little bit from a sprinkler. What could have gone wrong and what can I do better? I put a new connector on and the system is fine, but I was just really surprised. Do I need to put shrink wrap on these? Are they not allowed to be in direct sunlight? It’s a 95 degree day heatwave that this happened.

What are the panels specs and series/parallel configuration?

What inverer are you using? Code required an arc-fault system on the PV, which any UL1741 inverter should have?
The Arc fault detection would have caught that much sooner.

10 panels in series 250watt each. The voltage is usually around 240 total, and it was drawing about 7 amps at the time. My growatt said the PV input was about 1680 watts. It’s all 10awg pure copper cables I used.(not the aluminum coated kind).

The connectors were quite cheap like 11 dollars for 6 pairs on Amazon.

Solar Guppy said:

What inverer are you using? Code required an arc-fault system on the PV, which any UL1741 inverter should have?
The Arc fault detection would have caught that much sooner.

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I was using a growatt spf 5000ES. Ummm I don’t know if it’s an arc fault system? I need to learn about what that means. Do you think there was an arc in the connector?

Looks to me it is not UL listed and no mention of the required arc-fault detection

Yes, for sure there was arcing, that what generates the heat and melts the connectors. This is known to cause fires and why this was added to the NEC code in 2014 I believe.

Solar Guppy said:

Looks to me it is not UL listed and no mention of the required arc-fault detection

Yes, for sure there was arcing, that what generates the heat and melts the connectors. This is known to cause fires and why this was added to the NEC code in 2014 I believe.

Click to expand...

Wow. Ok so what can I do to prevent this from happening again? Is there some sort of fuse I can add to augment the system?

Was there an arc for an extended period of time while it slowly melted? Or did it happen very quickly?

Hard to say, either the wires were not crimped with a proper tool or the connectors were not mating well. I've used amazon connectors for the home runs and haven't had an issue.

If I recall correctly - the connector that had the arc was actually my first crimp. I bought a wirefy with the right die and everything. I remember struggling to get it right the first time, so maybe that was it. Now I want to go double check all the other crimps i did. yikes. thanks for all the advice.