25 amp circuit breaker does not trip?

Question

I have a 25 amp AC circuit breaker and am testing a 30 amp load on the circuit but the breaker still is not tripping. This is a generator that is rated for 3500 watts, and on top of that I am overloading the generator. (for your information)

I want the breaker to trip for testing purposes but maybe am missing something.

Answer 1

I'd try creating a short circuit to see if the breaker even works.

Answer 2

Just because the nameplate says 30amp that doesn't mean it will constantly draw 30 amp.

How do you know you are overloading the generator?

Answer 3

If the trip is not working when you put a continuous current through it then mayb if you put a surge of electricity through it then mayb this will be the answer.  have you worked the amps out, just because there is 3500watts doesn't mean there is 30amps.  

V = I/R

I = V x R

Answer 4

The breaker does not instantaneously trip at 25.1 amps.  The time-current characteristics (TCC) curve for breakers is rather slow at 30 amps.

I have the curve for a Square-D 20 amp breaker and at 120% of nameplate (24 amps) it will take over 60 seconds to trip.

At 20 amps it will take 400 seconds (over 6½ minutes) to trip.

Answer 5

u see everything depends on the make and model of the CB that will differ, but i ll tell u generally, 5 ampere more, in respect to 25 A,  wont be considered a fault for the CB, but it will consider it as an overload, this will buy more tripping time, again according to the CB overload tripping Charecteristics.

heres wt u have to do to get a best suited CB:

first u have to know alot about overcurrent protection schemes, in detail DISCRIMINATION, which is the theory and practice of how CBs react to overcurrent values.

search for a CB with high sensitivity, although it wud be most expensive, or u can get a CB that works at "extremely-inverse time characteristics" this will shorten the tripping time

still this needs a power engineer, especially protection engineer if available.

one last advice: BE EXTREMELY CAREFULL, OVERLOADING THE GENERATOR IS HAZARDOUS!!

get back to me for more info.

Answer 6

Change breaker types and instead of using a thermal breaker use a magnetic breaker. The magnetic breaker trip point usually is more precise and the breaker is usually faster than a thermal breaker. Look at:

http://www.alliedelec.com/Search/Product...

Mfr Part#: C25A1P-489

Allied Stock#: 342-0338

or talk to a supplier like graybar, summers electric. etc

Another possibility is using a fast acting fuse and fuse holder instead of the thermal breaker.