Common Molded Case Circuit Breakers - Change Value on Each Trip

[mtnelect]

Do common molded case circuit breakers change value each time they are tripped ?

On residential service calls, where a circuit breaker has tripped multiple times ... Does the trip value lessen on each trip ?

I have no proof of this, but have always replaced the circuit breaker with a new one ... For good measure.

 

[infinity]

I'm going to say no. Maybe after a few thousand cycles the mechanical parts will wear out but a basic circuit breaker is not going to "learn" anything.

 

[jim dungar]

Do common molded case circuit breakers change value each time they are tripped ?

On residential service calls, where a circuit breaker has tripped multiple times ... Does the trip value lessen on each trip ?

I have no proof of this, but have always replaced the circuit breaker with a new one ... For good measure.

Small circuit breakers can handle hundreds of full load trips, but they can only handle 1 full short circuit (max AIC). The failure mode is much more likely the contacts not the trip mechanism.

There is no history of breakers generally changing trip characteristics.

 

[ptonsparky]

My thoughts would be why is it tripping in the first place.

Doing a FOP test would clear the contact issue up.

 

[petersonra]

The trip point is going to be different every time for environmental and load reasons.

For instance, a 15 A cb that has been run at 15 Amps long enough to heat up will trip faster at 25 Amps than the same cb will that started cold.

Same thing applies for ambient temps. Will take longer to trip at 50 deg f than 100 deg f.

 

[mtnelect]

My thoughts would be why is it tripping in the first place.

Doing a FOP test would clear the contact issue up.

Most of the problems I encountered were due to overloaded circuits, where the homeowner kept resetting the breaker over a long period of time and most of the panels were "Zinsco". Also, some were connections to the "Busbar" which were obvious.

 

[mtnelect]

The trip point is going to be different every time for environmental and load reasons.

For instance, a 15 A cb that has been run at 15 Amps long enough to heat up will trip faster at 25 Amps than the same cb will that started cold.

Same thing applies for ambient temps. Will take longer to trip at 50 deg f than 100 deg f.

You are correct on the environment ... This was in the High Desert of Los Angeles County which were full of "Zinsco" panels. Very hot in the summer and very cold in the winter.

 

[ptonsparky]

Still, they should not be tripping. Overload, short circuit or poor connection are the options. It could be they were minimally sized to begin with.

 

[mtnelect]

Still, they should not be tripping. Overload, short circuit or poor connection are the options. It could be they were minimally sized to begin with.

I agree, these were all track homes that were mass produced around 1975 to sell fast and are now having problems. They all had two 15 amp circuits shared with the kitchen and diving room.

 

[ptonsparky]

Wow, a diving room. Must have been upscale tract homes.

I agree, these were all track homes that were mass produced around 1975 to sell fast and are now having problems. They all had two 15 amp circuits shared with the kitchen and diving room.

 

[Bill_F]

Hee hee.
Hate auto correct!

 

[Birken Vogt]

I have replaced a number of breakers over the years that were tripping inappropriately. I chalked it up to high resistance in the contacts.

 

[ptonsparky]

I have replaced a number of breakers over the years that were tripping inappropriately. I chalked it up to high resistance in the contacts.

Most likely.