circuit breaker vs. fuse

[Jraef]

So true but they will still just snap in a higher amp breaker when it starts tripping

True, albeit a little more difficult.

In the words of Ron White, "You can't fix stupid."

 

[kingpb]

Aren't breakers supposed to be replaced after tripping? If so, then single use for breaker is same as fuse. We all know that doesn't happen, but as long as we're being theoretical and all.

I will go on record as a breaker person. Seen to many blown fuses replaced with whatever they have on hand (wrong fuses), pennies, cable, pipe (as shown above), or whatever they can find.

 

[zog]

Aren't breakers supposed to be replaced after tripping? If so, then single use for breaker is same as fuse. We all know that doesn't happen, but as long as we're being theoretical and all.

Depends on the type of fault and type of breaker you are talking about. The OEM will have guideance for this in thier technical documentation.

 

[Jraef]

Aren't breakers supposed to be replaced after tripping? If so, then single use for breaker is same as fuse. We all know that doesn't happen, but as long as we're being theoretical and all....

Common misconception. I think it stems from the ANSI / NEMA test criteria for MCCBs that states (condensed version) that a breaker must trip within tolerance, be able to be reset, and trip again within tolerance. That's just where the testing stops, so theoretically a 3rd trip may not be within tolerance and the breaker would still meet this. But this is by no means the MAXIMUM DESIGN criteria, this is the MINIMUM TEST criteria. No manufacturer worth their salt is going to make one-shot circuit breakers.

 

[jim dungar]

Aren't breakers supposed to be replaced after tripping? If so, then single use for breaker is same as fuse. We all know that doesn't happen, but as long as we're being theoretical and all.

A molded case breaker is tested to pass many overload trips, it depends on the size, small frame can be more than 100 times). But a breaker is only intended to clear a single fault at its full AIC rating.

So if you know that a molded case breaker did not trip a fault near its capacity (i.e. your power system study shows the available fault current is <25% of its rating) there is no reason it could not be reset multiple time.

So it is imperative that you know the details behind why an OCPD operated.