What's safer - fuses or breakers?

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  #1  
Old 11-27-06, 02:20 PM
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What's safer - fuses or breakers?

I had a basement flood a while back and the solenoid for my well pump and pressurizer tank were under water and energised for what may have been several days. The CB did not open
(I've since replaced it) but it got me thinking about the long term reliability of mechanical circuit breakers.
It appears that the only advantage a breaker has over a fuse is the ability to turn it off or reset it. However, it's a mechanical device that seldom if ever gets tested or even exercised. A fuse relies on the known melting properties of metal while a breaker relies on a mechanical contact. It seems to me from a strictly safety standpoint, a fuse would be the way to go. Am I missing something?
 
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  #2  
Old 11-27-06, 02:22 PM
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Well, if these are running off the basement circuits, they should be GFI protected anyway. I know that GFI would trip in this situation, but maybe not a circuit breaker.
 
  #3  
Old 11-27-06, 02:52 PM
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Fuses and circuit breakers are all available with different trip curve characteristics. With fuses you have more options.

Regarding your situation. I doubt any fuse, breaker, or GFI would have tripped. This is what is so deadly about electricity and water. Enough current can flow to kill a person, but not enough to trip a breaker. The GFI would stay energized until something else, like a human, caused current to take a different path, then it should tip before that person is killed.

All breakers and GFI are supposed to be exersized. For breakers it should be once a year. For most GFI it is once a month.

While it is code legal to install certain things like sump pumps without using a GFI, I would use one anyway unless there is a problem running it without one.
 
  #4  
Old 11-27-06, 02:52 PM
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Breakers are much safer than fuses. In fact, many insurance companies will no longer issue policies on homes that have fuse panels, and they do everything by-the-numbers. Fuses certainly have their places, but a main panel is not one of them in my opinion. Fuses do offer better protection for specific applications, but not for general use.

* Fuses are too easy for a homeowner to oversize intentionally or accidentally, although some types of fuse base fix this problem the common Edison base style does not. Human error is probably the number one failure in any safety system.

* Fuse sockets expose live metal to a homeowner who's trying to replace one (often) in the dark.

* Overloaded fuses can explode and cause injury from the glass and fire from the molten metal filament.

* Standard breakers have both a thermal and magnetic trip mechanism which trips instantly on short circuits whereas fuses only have thermal leading to massive overcurrents and heating for short circuits.

* Breakers can have additional safety trip mechanisms such as GFCI and AFCI which are impossible to implement with fuses.

* Double pole breakers serving 240V loads have internal linkage to trip both hot legs in the event of a fault whereas a fuse will only open one leg leaving the other live to a faulted appliance.
 
  #5  
Old 11-27-06, 03:12 PM
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Question for Ben

Ben,

I have fuses in my home currently and a few GFI recepticles. If I understand correctly, you are saying that with fuses you can't have GFI for the whole circuit (as if you were using a GFI breaker), correct? You can still use GFI recepticles on a fused circuit, unless I am mistaken.

-Chris
 
  #6  
Old 11-27-06, 03:43 PM
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Fuses will trip everytime when needed.
Breakers are mechanical and do fail.
Fuses however can be replaced with larger ones too easily, thus defeating their purpose.
 
  #7  
Old 11-27-06, 04:22 PM
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> You can still use GFI recepticles on a fused circuit

Correct. GFCI receptacles are perfectly safe and effective on a fused circuit.

> with fuses you can't have GFI for the whole circuit

Right; for most applications this is not a problem, because GFCI receptacles are just as effective. A GFCI breaker (as opposed to a receptacle) is appropriate for a direct-wired spa, for example. Such protection cannot be provided directly with fuses.

There is also a newer technology called AFCI which can only be implemented in a breaker. AFCI protection can detect the type of sparks caused by frayed cords and hopefully prevent a fire.

> ...

Simply having a fuse panel in a home is not doom and gloom; it just requires diligence on the part of the homeowner (and previous homeowner(s)) to make sure that only the correct size fuses are used. Circuits with #14 wire use a 15A fuse, #12 wire use a 20A fuse, and #10 wire use a 30A fuse. Since the average homeowner does not know this, the fuse panel poses a latent hazard if incorrect fuses are installed.
 
  #8  
Old 11-27-06, 06:23 PM
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When I purchased my home and needed insurance my carrier at the time would not insure me because I had fused service. Actually, it was specifically beacause it was 60A fused service. 100A fused service would have been ok. The reasoning was because just what has been stated..it's easy to put in a higher rated fuse, or a penny, and create a fire hazard. Inquiring about the 60A vs. 100A, I was told that with less amps available, it is more likely that fuses will blow, so it is more likely that someone would change the fuses to avoid them popping.

It's by the numbers, but it makes no common sense. I could just as easily put my head in the oven with the gas on, and that would be a hazard as well.

Found another carrier who cared less about it, and they insured me. Since have upgraded to 125A breaker service, with plenty of circuits.

The one difference I found was that fuses were single use, and I was always out of the one I needed when I needed it.
 
  #9  
Old 11-27-06, 07:33 PM
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I've worked with/around electricity in residential, commercial and industrial settings. I even worked in an electrical generating facility for two years. I have never seen a "properly applied" fuse fail to blow in either an overload or short circuit application although I cannot say the same for circuit breakers.

HOWEVER, the key phrase is "properly applied". In non-residential environments the electrical systems are (usually) under the control of trained maintenance people and the wrong size or type of fuse for the circuit is extremely rare. The problem with fuses comes when the wrong fuse, or heaven forbid a penny or the like, is installed instead of the correct fuse.

So, in residential settings I think that circuit breakers are probably safer.
 
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Old 11-28-06, 09:05 AM
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> It's by the numbers, but it makes no common sense. I could
> just as easily put my head in the oven with the gas on, and
> that would be a hazard as well.

I think the difference is that the average person understands why putting your head in the oven is unsafe. I believe that most people do not know that overfusing circuits is unsafe -- or even that they are overfusing.

For example, the previous homeowner replaces all 15A fuses with 20A fuses (or even 30A). New owner moves in and someday down the line needs to replace a fuse. He takes the old burned out 20A down to the hardware, finds a matching replacement and installs it. The new owner is doing something dangerous that he isn't even aware of, and the only way he could know that he's doing something wrong is to take the cover off the panel and compare wire gauges.
 
  #11  
Old 11-28-06, 10:06 AM
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yep you're right.
 
  #12  
Old 11-28-06, 09:48 PM
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IPBrooks - Thanks for your sound reasoning regarding the disadvantages of fuses. Installing an over rated fuse is an obviously foolish and dangerous practice and probably the biggest disadvantage.

I'm still convinced that from a protection standpoint a correctly sized fuse is more reliable than a 30 year old breaker in a damp and moldy basement that hasn't been exercised in it's lifetime. Care to guess how many of those are around?

It's too bad that nobody was smart enough to size fuses physically according to their ampere rating.
 
  #13  
Old 11-29-06, 05:10 AM
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I agree that fuses, properly used are safer than circuit breakers, since there are no moving parts. Mechanical failure of circuit breakers can and does occur. What is not widely known is that circuit breakers are not switches, and should not be used as such. The proper way to excercise a circuit breaker is with all downstream components turned off. Otherwise, if done repeatedly, you run the risk of internal damage to the circuit breaker.
 
  #14  
Old 11-29-06, 06:20 AM
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Fuses are now sized by their current rating. The base has the center portion a different size for different amperages. Problem is older panels don't have the inserts or have them removed that block the wrong size fuses.
 
  #15  
Old 11-29-06, 01:13 PM
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Can you still get the fusestat inserts. I know you can still get the fuses.
 
  #16  
Old 11-29-06, 01:47 PM
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Wink

HOT TOPIC-- IE: grounds up or down...screws in plates, horizontal or vertical...Etc.


I like fuses, they don't lie. IF used correctly.
Breakers are great for convenience, and with the electronic advancements are becoming invaluable,However require maintenance.They are electro/mechanical.If we keep this in mind we'll all be fine.
 
  #17  
Old 11-29-06, 02:52 PM
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There have been some real disasters with breakers, Federal Pacific for example and I have seen Westinghouse breakers fail to open when they should too. The Westinghouse breakers were replaced with GE and then we found they would remain closed even when manually set to off. I prefer fuses but fuses nor breakers are the answer for all situations.
 
  #18  
Old 11-29-06, 10:59 PM
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I hear that zinsco breakers are another one to avoid like the plague.
 
  #19  
Old 11-29-06, 11:54 PM
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Most first generation anything, avoid.

cars, Bikes etc. Let them work the bugs out.

The older breakers of wich you speak, are notoriously bad.

However SQD had their own recall for their AFCIs'.
So just goes to show... Cutting edge has its' own "burn in" time.

Don't be the fool...Learn from him.

I still like fuses. Sometimes.. You must question progress.
 
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