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Originally Posted by seatonheating

I would think frying a transformer or circuit board would happen a lot quicker than what it would take to cook a wire.
That being said, I believe that a breaker is not sufficient enough to protect equipment and/or equipment components. By the time the breaker is tripped the damage has already been done to such sensitive devices. Am I wrong?

seaton: you are correct. For a non-motor circuit, one-time fuses will 'blow' at any excess current flow, without delay. One-time fuses would be more appropriate to protect circuits that do not involve any type of 'starting' currents. Like control circuits, electronic circuits, etc.
Breakers & time-delay fuses are meant to protect motor circuits, primarily, because of their being 'inverse-time' devices.

Richard

Originally Posted by bornriding

Why can't a circuit breaker be used here, just as easily & with the same protection.

In case you coudn't guess, I generally prefer breakers to fuses. Generally, the only time I use fuses is when the circuit I want to protect is too small ( current ) for a breaker.

Richard

I use breakers in main panels. I typically use fuses for retrofitting control circuits. If it is a new circuit I am putting in I use a breaker that I can set to what amp rating I need. Alot of the time on new installs if the size of the over current is unknown I will run a larger than required circuit and fuse it down. Pretty much it depends on the independent application for me.

Originally Posted by cjett

I sometimes see disconnects with breakers for AC's but I never see them for sale like this anywhere. Anyone else ever run across them?

i see them alot but only on 40 yr. old equipt. it's the evolution of what code calls for.
breakers and fuses both open faster the higher the spike over ampacity rating of said device. thats how you know its a shorted compressor when you find "both" fuses open in a disconnect.

I would think frying a transformer or circuit board would happen a lot quicker than what it would take to cook a wire.

That being said, I believe that a breaker is not sufficient enough to protect equipment and/or equipment components. By the time the breaker is tripped the damage has already been done to such sensitive devices. Am I wrong?

I sometimes see disconnects with breakers for AC's but I never see them for sale like this anywhere. Anyone else ever run across them?

Originally Posted by jbcrane

fuses and breakers protect the same thing. it basically comes down to application. In some places it is better to use a fuse over a breaker.
Can you give an example of when a fuse is BETTER than a breaker??

It also depends on what type of fuse you use; one time, dual element time delay, so on. I typically use fuses in disconnects on commercial units in some buildings i maintain. In this example one circuit that is sized large enough for 2 units can be broken down with fuses to protect the individual equipment.

Why can't a circuit breaker be used here, just as easily & with the same protection.

In case you coudn't guess, I generally prefer breakers to fuses. Generally, the only time I use fuses is when the circuit I want to protect is too small ( current ) for a breaker.

Richard

fuses and breakers protect the same thing. it basically comes down to application. In some places it is better to use a fuse over a breaker. It also depends on what type of fuse you use; one time, dual element time delay, so on. I typically use fuses in disconnects on commercial units in some buildings i maintain. In this example one circuit that is sized large enough for 2 units can be broken down with fuses to protect the individual equipment.

IMHO...

The most important aspect of protection is the detection of the high current condition and the reaction time of the protective device.

An ideal situation would be a device that prevented the wiring from exceeding its temperature limit while reacting to a high current draw from the equipment in a time frame that helped to prevent further damage.

Yes, fuses are available in increments that more closely follow the needs of a particular piece of equipment.

Originally Posted by Royster88

What is the advantage of fuses over circuit breakers?

The only advantage is that you can get fuses at a lower amp rating than breakers, which will allow for 'closer' protection of equipment.
There is not much difference between a dual acting fuse & a circuit breaker. HOwever, a one-time fuse & a circuit breaker are different in their ability to 'closely' protect a circuit.

All breakers & fuses, in distribution panels, are designed to protect the conductors.
All breaker & fuses in disconnects or within the equipment are sized for equipment protection.

Richard

I think it matters MORE WHERE the protection is located.
Circuit Breakers are located IN the distabution pannel, while Fuses are located in the disconnect pannel.
One protects the equipment, while the other protects the wire.
That having been said, what if the fuses are in the dist. pannel, and the circuit breaker is in the disconnect? I have seen this done.

Some breakers are designed to protect the equipment as well. Leiberts for instance will have an odd ball size breaker like 32 amps. Yet they are still protected by fuses. Interesting.

Originally Posted by beenthere

Breaker protects the wire.
Fuse protects the equipment.

That's interesting. You have given me something to think about.

Hmmm.

Breaker protects the wire.
Fuse protects the equipment.

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fuses and circuit breakers

What is the advantage of fuses over circuit breakers?