Why do we still use fuses? Question, not a statement!

[brian john]

Time isn't money when a feed water pump trips a breaker at 1:30 a.m. and it is at a boiler plant at Feb 02.Must get going.

I make money at that all the time, wake me up then I call a tech dispatch him. With a minimum 4 hours, plus mileage and any time on site, test equipment rental, seems like a cash producer to ME.

In addition if you get hurt do you think management will accept responsibility for your injuries, if you damage equipment do you think you will get a favorable review. In both cases, in my expierence management DID NOT stand behind their employee.

 

[e57]

This thread is great - lot of good info here.

I investigate EVERYTHING..time is money and safe is safe.

That comes from OSHA 1910.334, here is the rest of it.

(b)(2) "Reclosing circuits after protective device operation." After a circuit is deenergized
by a circuit protective device, the circuit protective device, the circuit may not
be manually reenergized until it has been determined that the equipment and
circuit can be safely energized. The repetitive manual reclosing of circuit breakers
or reenergizing circuits through replaced fuses is prohibited.

Note: When it can be determined from the design of the circuit and the
overcurrent devices involved that the automatic operation of a device was
caused by an overload rather than a fault condition, no examination of the circuit
or connected equipment is needed before the circuit is reenergized.

IMO a number of people are speaking from experiance... I'll speak to mine - when I was younger and dumber I went to a service call for an AC compressor and said 'oh tripped breaker'.... Flipped it. Fire ball... Big Fire Ball! Never did that again....

As for the fuse breaker debate - for certain items fuses are much better suited - I've seen a number of breakers fail to operate and far past thier trip curves, and seem to get worse when they don't trip. Just makes me leary on higher current, and higher fault current items. IMO The cascading effect of one failure protected by a failed device causes more damage and eventual catotrophic dead short failure - once again protected by the faulty device that may or may not operate as it should if at all. A fuse - even if it held right at or above its trip curve when it comes to a short will clear. But then again I have never heard of a ground fault protecting fuse.....

 

[ATSman]

This thread is great - lot of good info here.



IMO a number of people are speaking from experiance... I'll speak to mine - when I was younger and dumber I went to a service call for an AC compressor and said 'oh tripped breaker'.... Flipped it. Fire ball... Big Fire Ball! Never did that again....

As for the fuse breaker debate - for certain items fuses are much better suited - I've seen a number of breakers fail to operate and far past thier trip curves, and seem to get worse when they don't trip. Just makes me leary on higher current, and higher fault current items. IMO The cascading effect of one failure protected by a failed device causes more damage and eventual catotrophic dead short failure - once again protected by the faulty device that may or may not operate as it should if at all. A fuse - even if it held right at or above its trip curve when it comes to a short will clear. But then again I have never heard of a ground fault protecting fuse.....

Ah....the GF issue. IMO the biggest advantage of breakers over fuses is the GF feature. As I recall one stat....70% of all faults start out as a ground fault. Although sometimes GF protection can be too sensitive and cause headaches. How many time have you heard of a shorted 277V lighting ballast (or electrician's burnt screwdriver tip) cause the short to go through a 20A branch breaker all the way up the system to trip the building's 4000A main breaker. The reason for this being that the dist. system design did not spec second level GF protection on the feeder breakers because of added cost (per code, GF is only required on the main.)

As for the breakers not operating, well that's a PM issue.

 

[weressl]

I work for a sewer company, 20 different plants, hundreds of different fuses. I cant carry all of them on my truck. What advantage does a fuse have over a circuit breaker? Once you find the problem, you can reset the circuit breaker. If it is a fuse and you don't have a spare you have to go get one.

Circuit breakers are the primary and prefered protective devices for general distribution. Fuses only need to be used for the special occasions mentioned.

Did I miss it or nobody mentioned single phasing protection advantage by the breakers? Fuses with mismathced characteristics, size and type are a big drawback for 3 phase applications in real life. Add coordination falling appart on top of that, and you have a mess on your hand after while.:roll:

 

[boboelectric]

This thread is great - lot of good info here.



IMO a number of people are speaking from experiance... I'll speak to mine - when I was younger and dumber I went to a service call for an AC compressor and said 'oh tripped breaker'.... Flipped it. Fire ball... Big Fire Ball! Never did that again....

As for the fuse breaker debate - for certain items fuses are much better suited - I've seen a number of breakers fail to operate and far past thier trip curves, and seem to get worse when they don't trip. Just makes me leary on higher current, and higher fault current items. IMO The cascading effect of one failure protected by a failed device causes more damage and eventual catotrophic dead short failure - once again protected by the faulty device that may or may not operate as it should if at all. A fuse - even if it held right at or above its trip curve when it comes to a short will clear. But then again I have never heard of a ground fault protecting fuse.....

Now an ac .RTU that trips a c.b. will get a throurgh study,before turning the gas back on.

 

[weressl]

This thread is great - lot of good info here.



IMO a number of people are speaking from experiance... I'll speak to mine - when I was younger and dumber I went to a service call for an AC compressor and said 'oh tripped breaker'.... Flipped it. Fire ball... Big Fire Ball! Never did that again....

As for the fuse breaker debate - for certain items fuses are much better suited - I've seen a number of breakers fail to operate and far past thier trip curves, and seem to get worse when they don't trip. Just makes me leary on higher current, and higher fault current items. IMO The cascading effect of one failure protected by a failed device causes more damage and eventual catotrophic dead short failure - once again protected by the faulty device that may or may not operate as it should if at all. A fuse - even if it held right at or above its trip curve when it comes to a short will clear. But then again I have never heard of a ground fault protecting fuse.....

You are bringing up examples of misapplication of breakers.

FYI a fuse will not clear a fault either when the fault current exceeds its interrupting rating. A fuse will react the same way to a ground fault as an ordinary circuit breaker would.