Circuit breaker spring tension-effect on operation?

[cryomark]

I have 3 Westinghouse MC3800 frame CBs (~1980 vintage) that were removed from service for various disfunctions. I opened them up to determine if rebuild or replacement was the better option.

All had very gummy lubrication which appeared to be the problem with 2 of them. The 3rd has other problems as well.

First, the main tensioner springs (2) are painted a different color(blue) from those in the other 2 CBs(yellow). The spring wire appears to be very slightly heavier. The force required to reset this blue breaker is much higher than the yellows~2x. The arc chute and arc contacts show significant metal splash on all 3 Ø though the main current carrying contacts look fine.

How does increase in the spring constant affect the opening characteristic of the CB?

 

[dpc]

I basically have no idea, and not that it will stop you, but just want to mention that molded case circuit breakers are not really considered maintainable. Any time you open one up, it's no longer a UL-recognized device.

Of course lots of people do work on them but I'm sure the manufacturer doesn't recommend it.