Has anyone seen anything similar to this on a PV system.

[aelectricalman]

Look at the pattern for which the wires are burned. Notice gradual lessening degree of burn from top to bottom. I do not know the voltage on the system. I can speculate since the wires are taped B-O-Y. I know the obvious answer, but I want to see if anyone else hits on what else I think it could be. Any thoughts?

 

[ggunn]

Look at the pattern for which the wires are burned. Notice gradual lessening degree of burn from top to bottom. I do not know the voltage on the system. I can speculate since the wires are taped B-O-Y. I know the obvious answer, but I want to see if anyone else hits on what else I think it could be. Any thoughts?

Does it have to do with the copper corrosion I see? Dissimilar metals, maybe?

 

[aelectricalman]

I actually don't know what caused this. I am speculating. It doesn't appear there is copper corrosion, just some burning going on.

 

[wirenut1980]

Where in the PV system are we looking? Are those neutrals for branch circuits on the AC side? Or something on the DC side? What's on the other end of those white wires?

 

[ggunn]

I actually don't know what caused this. I am speculating. It doesn't appear there is copper corrosion, just some burning going on.

That green I see on the copper next to the bus bar isn't corrosion?

 

[augie47]

The nature of the discoloring seems to indicate a poor connection of some type.
What is the condition of the neutral main feeder ? The entire bar looks overheated.

 

[jaggedben]

There's definitely copper oxidation that's happened, but galvanic corrosion wouldn't have discolored the insulation on the wires. I would guess overheating from overcurrent.

I'm guessing that this is AC because the photo caption says 'load center', but are we looking at inverter interconnections or loads? My best stab in the dark is that someone didn't obey the 120% rule.

 

[ggunn]

There's definitely copper oxidation that's happened, but galvanic corrosion wouldn't have discolored the insulation on the wires. I would guess overheating from overcurrent.

But corrosion could have degraded the connections and made them resistive, then under high current conditions the resistance would have caused heating.

 

[K8MHZ]

The nature of the discoloring seems to indicate a poor connection of some type.
What is the condition of the neutral main feeder ? The entire bar looks overheated.

Looking closely it appears the bar is fed at the top of the pic. If the connection there was poor and generating heat, there would be a thermal gradient down the bar.

 

[jaggedben]

Looking closely it appears the bar is fed at the top of the pic. If the connection there was poor and generating heat, there would be a thermal gradient down the bar.

That's why I was thinking that the PV and utility feeds were both connected at the same end on a bar not rated 120% of the max current. There would be more current nearer the connection points, and thermal overheating could transfer to the wires as you describe. If it were breakers, this would be in violation of 705.12(D)(7). But this is the neutral bar, so that has me wondering. Hope the OP comes back and tells us the deal.

 

[Article 90.1]

My guess: The screws on the neutral bar are almost flush with the bar so they are probably way overtightened. The cross sectional area of the conductors has been reduced to a point where they are now the equivalent of a smaller gauge conductor. I know this may seem like an odd guess, but I have seen it on solid neutrals in a resi. service.

I think the "PV system..." part is a red herring in this case and this problem has nothing to do with said system.

Second guess, if I'm allowed one, 3 phase panel = MWBC's = CCC's of MWBC'c are not on separate phases.

 

[Steven M. H.]

burnt wires

burnt wires

point of connection probably wasnt at opposite end of bussing from feeders

 

[ejerrym]

Seen it Before....Maybe

Seen it Before....Maybe

Looks like two sources of out of phase voltage were applied to the circuit. I saw very similar damage to electrical components when generator power and grid power were "accidently" applied to a circuit. Not only that, but the damage was widespread throughout the office complex.