Circuit breaker lug corrosion

[drktmplr12]

Recently a customer told me he has replaced a circuit breaker once a year because the B phase lugs are corroding in place. He's on the 3rd one now. They are SQD FAL breakers, 125 A frame. Assuming all copper conductors and lugs rated for copper/aluminum.. any theories on what could cause just the B phase to corrode?

 

[Jraef]

Moisture infiltrating the conductor insulation somewhere and wicking along the wire strands to get on the lug. A megger would probably confirm that.

 

[ptonsparky]

Moisture infiltrating the conductor insulation somewhere and wicking along the wire strands to get on the lug. A megger would probably confirm that.

We had this happen on a 400 amp IIRC. Water seeped in at the service point and followed it in 20ft or so. We nicked the conductor insulation at a low point in the loop to get it to drain. First class hack remedy for sure. You would have had to see the project to understand.

 

[Jraef]

Yeah, I mentioned it because I've seen it too. 500MCM cable going to a refrigeration compressor and the conduit went under ground, where it would fill with the condensation water off of the coils (bad drainage plan). The Soft Starter would trip on Short Circuit, then it would take a day or so for me to get out to the site (fish processing plant) and by then, everything dried out because the compressor hadn't been running. I meggered the wires and motor and didn't find anything, but after the 3rd go around I noticed the corrosion on only one lug. So I got it running and stayed at the fish processing plant for the night to see it trip and when it did, the megger saw the leak.

 

[kwired]

One thing I kind of dislike about typical N3R Safety switches, Loadcenters and other similar items - the top entry hub is directly over main supply lugs 99% of the time. Even if you don't have moisture migrating inside conductor insulation, any condensation that occurs within the raceway still has good chance of following conductors right into the lugs.

 

[MrJLH]

Recently a customer told me he has replaced a circuit breaker once a year because the B phase lugs are corroding in place. He's on the 3rd one now. They are SQD FAL breakers, 125 A frame. Assuming all copper conductors and lugs rated for copper/aluminum.. any theories on what could cause just the B phase to corrode?

Is this by chance used on a pump application with on/off control in a outdoor rated encosure?

 

[drktmplr12]

Is this by chance used on a pump application with on/off control in a outdoor rated encosure?

yes, water production well that turns on and runs continuously for a number of hours or even days before switching off.

moisture intrusion to the insulation was my first guess, but that doesn't explain why the load side of the same phase conductor is also corroded, unless water (or corrosion) is making its way through the contacts inside the breaker.

part of the project is to replace the service conductors and feed the panel from another location. if the insulation is cause, replacement should solve this problem

edit: i now realize i did not mention that the load side of the breaker was corroding as well.

 

[drktmplr12]

One thing I kind of dislike about typical N3R Safety switches, Loadcenters and other similar items - the top entry hub is directly over main supply lugs 99% of the time. Even if you don't have moisture migrating inside conductor insulation, any condensation that occurs within the raceway still has good chance of following conductors right into the lugs.

bottom feed, in this case. very good point.

we find that even with 4X drains and meyers hubs, moisture is still an issue. we have gotten away from ever allowing top entry to 3R or 4X enclosures unless absolutely necessary

 

[kwired]

yes, water production well that turns on and runs continuously for a number of hours or even days before switching off.

moisture intrusion to the insulation was my first guess, but that doesn't explain why the load side of the same phase conductor is also corroded, unless water (or corrosion) is making its way through the contacts inside the breaker.

part of the project is to replace the service conductors and feed the panel from another location. if the insulation is cause, replacement should solve this problem

May or may not directly involve the contacts, but if it enters the top side of a pole, it is most likely to drain out the bottom side of same pole when breaker is vertically mounted

 

[Jraef]

May or may not directly involve the contacts, but if it enters the top side of a pole, it is most likely to drain out the bottom side of same pole when breaker is vertically mounted

Yep. Breakers are not sealed.

 

[MrJLH]

yes, water production well that turns on and runs continuously for a number of hours or even days before switching off.

moisture intrusion to the insulation was my first guess, but that doesn't explain why the load side of the same phase conductor is also corroded, unless water (or corrosion) is making its way through the contacts inside the breaker.

part of the project is to replace the service conductors and feed the panel from another location. if the insulation is cause, replacement should solve this problem

edit: i now realize i did not mention that the load side of the breaker was corroding as well.

Might want to consider adding a space heater, but that would depend on the enclosure type.

 

[kwired]

Might want to consider adding a space heater, but that would depend on the enclosure type.

That depends on the reason there is moisture present. If it is water migrating inside conductor insulation because of poorly done drip loop on overhead conductor transition, it won't do anything to stop that.