Circuit Breaker Question

[jeg223]

Has anyone heard of or experienced a "dead zone" in a circuit breaker? For example, a 20A breaker failing to open at 60A. I know circuit breakers can fail like any other device, but this is supposed to happen with an otherwise functional device. Almost like a resonance where the breaker doesn't see the over current condition because of the changing AC power.

 

[MikeMl]

How long was the 60A applied to the breaker? Have you studied the time-delay characteristics of circuit breakers?

 

[jeg223]

The 60A would be applied indefinitely if the breaker doesn't open. I know the time delay curves of the breakers are shown on the data sheet. 60A through a 20A breaker should trip in less than 1 second, but the supposition is that breaker wouldn't trip at all.

 

[colin55]

Have you changed the circuit breaker with another to see if the exact same fault exists?

 

[crutschow]

Has this happened to you, or is it just something you've heard about?

Sounds rather strange to me.

 

[cobra1]

Circuit breakers use Time vs Current to operate, if a high amp spike hits the breaker it can enter a "deadzone" where the appliance will cook before the breaker trips out. However this can only happen for a short time, the breaker would eventually trip out. I would not think that you could hold 60A on a 20A breaker indefinatly.

 

[jeg223]

This is just something I've heard about. I didn't think the 60A would pass for a significant amount of time.

 

[PatM]

Good preventive maintenance for circuit breakers should include periodic exercise of the operating mechanism. A better practice is to exercise the trip latch mechanism since it can seize due to lack of use.
I always exercise my breakers at least one a year.