insulation integrity

[ardy]

I reset a small cb on a 20amp gp circuit and go on if it holds. For my own piece of mind, I pencil in the date and circuit # inside the door of the panel.If I have a small motor such as a condesate or small boiler feed pump I reset the ol and watch for awhile and go on. Large motors I will Use my ohmmeter and see if it went to ground, if not I reset or replace fuse, ampmeter and keep eye on it. A large md panel is another story, I always open all loads before the ocp is reset. I will use my ohmmeter on the conductors of each load and when I am satisfied that a pnl is safe to energize I do that one at a time. If there is a mcc on that mdp it will be the last load that gets restored. Nine times out of ten your culprit is there.

 

[infinity]

Darn few I imagine.

For me I will be honest, it depends on a lot of factors.

A 20 amp branch circuit supplying GP outlets?

Heck no, I am gonna go over and reset the breaker.

A 400 amp 480 volt feeder?

I will be doing some investigating before reseting but if I find an obvious fault not related to the conductors I will not be megging them.

This is a common sense approach. I certainly wouldn't want to be turning on the 400 amp 480 volt feeder that had a bolted fault at one end.

 

[Pierre C Belarge]

Darn few I imagine.

For me I will be honest, it depends on a lot of factors.

A 20 amp branch circuit supplying GP outlets?

Heck no, I am gonna go over and reset the breaker.

A 400 amp 480 volt feeder?

I will be doing some investigating before reseting but if I find an obvious fault not related to the conductors I will not be megging them.

I will say that this is exactly how I was taught to work.
This is really a very interesting topic that I think will see more ink in the future, as more and more circuit breaker are getting older, and may not have been maintained. Because of this, the CB may not operate correctly, letting more current flow during an event than the conductor is permitted to conduct... leading to more testing of the conductors.
Just my thoughts.

BTW... how many will perform a service upgrade, reusing the "old" circuit breakers in the existing panel (to save some money). They may have been in the original service 30-40 years, now they may be in the "new" service just as long....HMMMMMMM

 

[zog]

oops, I had the wrong article, thanks for the correction. To jump back into this dscussion I (and everyone else at my company) megger the downstream side every time before resetting a breaker that has tripped on ST, INST, or GF (Or if the cause of the trip is unknown). Now I am refering to 480V drawout breakers in substations we dont ever work with little molded case breakers. Would I megger the load if one of my breakers at home tripped? No, I dont think that is the intent of this article.