Breaker Contact Resistance by Type

[adamwilson]

Which of these contact resistance (in micro-ohms) readings are passing?

A: 3200A Masterpact Breaker: A - 1252, B - 1300, C - 1171
B: 400A Eaton Molded Case Breaker: A - 850, B - 772, C - 813
C: 1200A VCP-W Breaker: A - 150, B - 151, C - 145
D: 15KV GE OCB Breaker: A - 175, B - 300, C - 425

What do you guys think? everyting seems high to me

[Kalbi_Rob]

Which of these contact resistance (in micro-ohms) readings are passing?

A: 3200A Masterpact Breaker: A - 1252, B - 1300, C - 1171
B: 400A Eaton Molded Case Breaker: A - 850, B - 772, C - 813
C: 1200A VCP-W Breaker: A - 150, B - 151, C - 145
D: 15KV GE OCB Breaker: A - 175, B - 300, C - 425

What do you guys think? everyting seems high to me

Per NETA, there cannot be 50% difference between readings, thus you take the lowest reading and multiply by 1.5, and the highest reading cannot exceed that value.

D is failing since 175*1.5=262.5, and both b and c are higher than 262.5

As a general look, A, C and D look abnormally high with regards to expected readings, but in spec per NETA.

[SecondGen]

Per NETA, there cannot be 50% difference between readings, thus you take the lowest reading and multiply by 1.5, and the highest reading cannot exceed that value.

D is failing since 175*1.5=262.5, and both b and c are higher than 262.5

As a general look, A, C and D look abnormally high with regards to expected readings, but in spec per NETA.

Agree that D looks pretty bad and the others are really high. Just knowing from experience that those specific breakers are way out of normal range, except maybe the molded case. I'd probably write up A and C as well in the real world.

Question could probably use some language that specifies NETA. If I wasn't going off NETA, all would probably fail by my standards, except the molded case, making my answer B.

[bob152637485]

Per NETA, there cannot be 50% difference between readings, thus you take the lowest reading and multiply by 1.5, and the highest reading cannot exceed that value.

D is failing since 175*1.5=262.5, and both b and c are higher than 262.5

As a general look, A, C and D look abnormally high with regards to expected readings, but in spec per NETA.

Thank you for the informative reply, I feel like I have come across this type of questions before, and now I know what to look for.