Bad terminals in service

[darekelec]

I upgraded a residential 100 amp service and noticed that some connections were ‘rusted’ on the service I took apart. Other connections were perfectly fine. I can’t find a reason or pattern for this nor explanation of reaction that happened.
bad connections have white powder around them.
The service was in a damp basement and Was 10 years old so maybe it survived Sandy hurricane. But doubtful it was flooded.
the bad connection were only in meter cans.

what could be the reason of the ‘rusted’ connections?

 

[Buck Parrish]

Heat could cause the metal to deteriorate. That connection may have been a little loose. Or to small for the current. In the field they call that "eat up" In a sentence. What's wrong with it? It's ate up, or In the south " it's eat up"

 

[Hv&Lv]

Water (moisture) intrusion.
Water can enter a cable exposed to the weather (up top) and the water can run through the cable and leak out on the connections. It’s the reason we use a “drop loop” for the service connections.

 

[FionaZuppa]

Dissimilar metals, leaching of chemicals from insulation, poorly made fitting.

It's all AL fittings?

 

[synchro]

The black conductors seem to be smaller gauge than the ones with red tape on them. If that's true then they may have gotten hotter and that accelerated the corrosion.

 

[darekelec]

There was no water intrusion. Underground service entered the 2 meter bank enclosure from the bottom.
it’s a damp cellar . Very unlikely it was flooded by Sandy hurricane.

black and white wires are smaller than red (2 awg and 2/0 awg) . I think installers didn’t have enough of 2 awg wire on truck so they used bigger wire. We will never know the torque of terminals it was tightened but I think it was fine.

2 panels for 2 apartments had 100amp mains .
lugs seem to be light as aluminum. I attached a photo of one.
I think it was a combination of all the factors. Corrosion of Dissimilar metals accelerated by damp environment and undersized cable.
I have 208V Y system here so neutral wire had a lot of amps on it although it was single phase service.
the service was calculated most likely for 3 story apartment and 1 floor 1 bedroom apartment that was used as a recording studio. So the service was maxed out.
The service was installed 10 years ago and passed city inspection.
Luckily nothing bad happened because new owner upgraded the service.

At some point of my life I wanted to study fire science and join fire department to be like Robert DeNiro in the movie ‘Backdraft’.

 

[Hv&Lv]

I have witnessed MANY installations that have water intrusion with UG services also. Water comes in the wire at the top of the pole, or the PMT gets flooded, and it runs in from there

 

[oldsparky52]

I have witnessed MANY installations that have water intrusion with UG services also. Water comes in the wire at the top of the pole, or the PMT gets flooded, and it runs in from there

I was working at a gas station on wiring the new dispensers and I noticed the service disconnect (located in the back room of the C-Store) had rusty water marks on the bottom of the enclosure. I asked the store owner about it and he said it (disconnect) drips water when it rains. Well this was puzzling since the service lateral was underground and came up into the bottom of the disconnect.

Being the inquizitive kind of guy I am, I investigated. Turns out there was no drip loop at the pole mounted transformer, the wire came up out of the pipe and connected directly to the transformer (looking up). So when it rained, the water ran down the wire inside the insulation and came out at the disconnect in the back room of the C-Store.

 

[hbiss]

Being the inquizitive kind of guy I am, I investigated. Turns out there was no drip loop at the pole mounted transformer, the wire came up out of the pipe and connected directly to the transformer (looking up). So when it rained, the water ran down the wire inside the insulation and came out at the disconnect in the back room of the C-Store

I would imagine it forms a pretty good siphon.

-Hal