Fuses or Circuit Breakers-Your Opinion?

[al]

In my view fuses are a much more reliable overcurrent device than circuit breakers. They can be in service for decades and then operate properly, whereas circuit breakers may not. What is your experience?

 

[SEO]

They both have their place in the industry. Fuses have a wide range of protection from less than an ampere up and they do open. Circuit breakers on the other hand have come a long way in development with the electronic type , etc. Have you ever seen any of the following a gfci fuse, an arc fault fuse or a shunt trip fuse?

 

[zog]

Fuses are good for some basic overcurrent proections tasks and are inexpensive.

Breakers offer many different options for selective coordinations (LT, ST, INST, GF, I2T, U/B, etc) for overcurrent, plus about 100 different parameters for trip inputs. Circuit breakers can be reset without having to be replaced. Modern trip units allow settings to be changes as your system changes (Fuses you need to buy new ones if something changes). Breakers can monitor your system parameters and send that info to your intranet, we even have breakers that monitor loads and send a text message to the maint manager when an overcurrent or fault condition exists. And I see breakers everyday for the 1920's, 1930's, and 1940's. With a little Preventative Maintance those breakers will last for a hundred years (Todays plastic junk never will but the old ones built like tanks last forever).

 

[zog]

In my view fuses are a much more reliable overcurrent device than circuit breakers.

How would you know? You cant test a fuse to see if it will blow when its T/C curve says it will, breakers you can test easily to see if they will meet the T/C trip times.

 

[iwire]

How would you know? You cant test a fuse to see if it will blow when its T/C curve says it will, breakers you can test easily to see if they will meet the T/C trip times.

I don't think there is any question at all that a fuse will trip unless the rules of nature change. Can you point any outside source describing the failure of a fuse to open?

The factory tests batches to ensure proper operation.

I know that you know dozens of ways breakers will fail to operate.

BTW, it is my understanding that recent changes to the NEC brought on by Bussman have made it very difficult to achieve proper selective coordination with circuit breakers in premises wiring systems operating below 600 volts.

Don't take any of this wrong, certainly breakers have a place. I guess Al should have set up some perimeters. Is he talking about homes, businesses, light industrial, heavy industrial or utility power distribution. :smile:

 

[ivsenroute]

Circuit breakers are more of a convenience than fuses but fuses are still in use in all aspects of electrical work, especially motor controls and will be around for a long time.

It is cheaper and quicker for a homeowner to go to a panel and flip a breaker after an overload rather than keep buying fuses.

Upgrading fuses because of constant trips is however a problem and is easily done by a homeowner. How many fuse panels did you see with overfusing?

Ultimately, in the residential environment, breakers are also safer (as long as they work) but I can certainly see a higher failure rate of breakers over fuses because of all of the mechanical parts that can get stuck over time.

 

[SEO]

It is cheaper and quicker for a homeowner to go to a panel and flip a breaker after an overload rather than keep buying fuses.

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Fuses are much easier to tamper with. Before type "S " fuses were required it wasn't uncommon to find 30 fuses on 15 ampere circuits. Ever see a penny behind a fuse?

 

[zog]

I don't think there is any question at all that a fuse will trip unless the rules of nature change. Can you point any outside source describing the failure of a fuse to open? [/quate]

Opening and opening when it is supposed to are very different things.

IThe factory tests batches to ensure proper operation.

Same for breakers, batch testing is a joke when you look at the numbers.

II know that you know dozens of ways breakers will fail to operate.

More than dozens My point is they can be tested to ensure they still operate correctly, fuses cant without destroying the fuse so the relibility comment by the OP cannot be justified.

IBTW, it is my understanding that recent changes to the NEC brought on by Bussman have made it very difficult to achieve proper selective coordination with circuit breakers in premises wiring systems operating below 600 volts.

Figures, thanks Bussman.

IDon't take any of this wrong, certainly breakers have a place. I guess Al should have set up some perimeters. Is he talking about homes, businesses, light industrial, heavy industrial or utility power distribution. :smile:

You are absoutly correct, and I agree that both fuses and breakers have thier places to be applied. there are many factors to be considered when making these decisions. It is like the old Mary Ann or Ginger question, all depends on the circumstances.

 

[brian john]

At one time there was an issue with fuse degradation, due to the change in shape of the soldered/welded ends deforming during motor/transformer inrush currents. Bussman has resolved this issue I am told and I would assume other manufactures follow suit.

 

[acrwc10]

Have you ever cut open a large fuse to see what is inside then ? I recently did (just out of curiosity) the smaller residential type 90 amp buseman no time delay or any special rating has an element that appears much larger then a 600 amp current limiting 225k interrupting rated fuse. I'll try to post a picture of the inside of the 600 ampere fuse.

 

[Goroon]

Never and Easy Choice

Never and Easy Choice

Application, Environment and Safety.
Those are the three considerations I use in determining what to use. Age and Temperature adversely affects fuses more than CB's, 10% rating reduction per 10 degree C if I remember correctly. A MFG [as will I] often will recommend replacement of larger fuses in IGBT systems every 5 years due to heat degradation (continuous 80% loading) in PM work to prevent failure. Fuses have faster clearing times that protects wires and equipment. It is better to have a CB where un-trained personnel or frequent service is involved. CB's are my preferred short-circuit ground fault protection as the primary and fuses selected and installed for individual loads. SWD CB's are rated to switch on and off loads and work great for transformer primary?s and secondary. Cost of circuit breakers and Fuses is more or less Equal when keeping 3, 6, 9 spare fuses versed the down time if not available. CB's in Control circuits can also be selected by Class. Larger CB's can be repaired and uniquely adjusted.

 

[tom baker]

For the typical motor, say 5-25 or 50 hp, properly sized fuses offer better protection than a TM circuit breaker or a IT breaker. The fuse can be sized much closer to the FLA setting, eg for 12 FLA motor the fuse could be 15 amp and a circuit breaker may be up to 250%.