Are fuses safer than breakers?

[drcampbell]

I can set up a home test that can prove just about any scenario I want. ...

Including selecting a fuse with an inadequate A.I.C. capability. Do that and the fuse element may melt and/or vaporize, but the arc inside the fuse body won't be extinguished and the current won't be interrupted. (metal vapor is a fairly-good conductor)

 

[Sberry]

I can set up a home test that can prove just about ant scenario I want.
The reason that series ratings, of fuses protecting breakers, must be 'tested' is that some breakers can definitely open and clear some faults before some fuses can. It can only less than 50' of #12AWG to prevent both fuses and breakers from entering the instantaneous portion of their trip curves.

I recall a long circuit for a temp, cords with a 16 on the end and I did something dumb and dead shorted it, didn't dump the breaker. Seems it had 100 ft of 12 and 75 ft of mix connected. I am not sure how long it would have taken but it wasn't instant.

 

[Joethemechanic]

Go figure, they still make them. Not sure why you'd want to use one though

SIEMENS CANADA LFC211N 2 Pole 30Amp 120/240V Siemens Disconnect Fused

www.gescan.com

 

[LarryFine]

Go figure, they still make them. Not sure why you'd want to use one though

Small motors?

 

[garbo]

I can set up a home test that can prove just about ant scenario I want.
The reason that series ratings, of fuses protecting breakers, must be 'tested' is that some breakers can definitely open and clear some faults before some fuses can. It can only less than 50' of #12AWG to prevent both fuses and breakers from entering the instantaneous portion of their trip curves.

Thanks. Never know about the 50' portion. Have seen residential central AC condensing units stating to use a certain size fuse for protection but most times they only have the two pole breaker for protection.

 

[garbo]

The last time that I installed a plug fuse safety switch was back in the 1970's that had a 3 amp fuse for three fire alarm bells in a triplex apartment. Wonder if most inspectors or AHJ 'S would ever allow them in a house or apartment due to dangerous possibilities of installing too large of a fuse. I usually P touch fuse ampere to use on all fusible safety switches in commercial sites.

 

[Besoeker3]

We regularly use breakers with no problem.

 

[Joethemechanic]

Small motors?

No doubt. I used to see them on small motors all the time. But plug fuses? And it isn't cheap. 100 bucks. I think I can remember them being about $15

 

[drcampbell]

... And it isn't cheap. 100 bucks. ...

It's CDN$98. Don't forget to apply the applicable exchange rate.

Currency Exchange Table (Canadian Dollar - CAD) - X-Rates

This currency rates table lets you compare an amount in Canadian Dollar to all other currencies.

x-rates.com

 

[petersonra]

You used to be able to buy a circuit breaker that you could exchange for the screw in fuses. That way at least there was less incentive to put a penny behind the fuse if you had it blow and had no spare.

 

[LarryFine]

You used to be able to buy a circuit breaker that you could exchange for the screw in fuses. =

Still in stock at my local HD:

Cooper Bussmann 15 Amp Plug Type Circuit Breaker BP/MB-15 - The Home Depot

Visit the Home Depot to buy Cooper Bussmann MB Series 15 amp Mini-Breaker Plug Fuse BP/MB-15

www.homedepot.com

Cooper Bussmann 20 Amp Plug Type Circuit Breaker BP/MB-20 - The Home Depot

Visit The Home Depot to buy Cooper Bussmann MB Series Silver 20 Amp Mini Breaker BP/MB-20

www.homedepot.com

 

[Jraef]

Let's face it, modern breakers make everything dummy proof.

Dummy resistant…
NOTHING is dummy proof, because nature keeps creating dumber dummies.

 

[garbo]

1) I had an electrician tell me that for residential panels the old bussmann glass fuses were safer than circuit breakers.

He said that sometimes a breaker won't trip whereas a fuse will open the circuit.

I do realize that people put pennies behind fuses or over size a fuse that keeps blowing in an attempt to fix the problem and that this makes fuses unsafe.

Your thoughts.

2) Is it possible to still buy the old bussman glass fuse boxes?

3) My hunch is the NEC (about to take the course) no longer accepts these for residential service?

While attending a great Vo Tech school back in the 1960's our teacher asked what would clear faster a normal plug in residential circuit breaker or a non time delay 15 & even a 20 amp . So I wired in a 15 amp circuit breaker in series with a fuse holder. On a dead short the 15 & 20 amp fuses always cleared while two different brands of 15 amp circuit breakers stay on. Circuit breakers in my opinion is the only way to go in houses and commercial sites. I prefer a fused safety switch close to any motor. So many times I had to remove load wires off of a fused safety switch to run a welder for short periods and would change fuses .

 

[ATSman]

I found this closed thread from 2007: https://forums.mikeholt.com/threads/fuse-or-breaker.36571/
One thing that wasn't mentioned although post #33 touched on it was the subject of Interrupting Rating (AIC) of breakers vs fuses.
I seem to recall that breakers can't react fast enough compared to a class J Current Limiting fuse which can open in 1/4 of a cycle. Which is why air frame power circuit breakers are fitted with CL fuses when used in main switchboards in large cities where the available fault currents can come close to 200KA.

 

[brycenesbitt]

Fuseable panels, for residences, fell out of favor almost 60 years ago, which is just about as long as they were in common use.
I have never seen any proof they were 'safer' than breakers. There is little in the world that is 99.999 sure, so based on the shear number of residential breakers sold over the past 70 years it is no wonder you can find examples of failure to open/trip.

This article from IEEE Access elaborates on that topic:

https://inspectapedia.com/electric/Circuit-Breaker-Defects-Aronstein-IEEE-2018.pdf

"Molded Case Circuit Breakers- Some Holes in the Electrical Safety Net"

In particular

There's a particular related set of breaker brands that on the bench and in the real world don't do the very thing they were designed to do.

Here's a picture of a Type S rejection base from USA knob and tube retrofits:

 

[winnie]

Back in college, hanging out with nerdy friends discussing how we would do things if we had money to burn, I decided it would be great to have panels with circuit breakers in series with slightly higher rated fuses.

The idea us that the circuit breaker would trip first if it were properly functioning, but the fuse would protect the circuit if the breaker failed.

Of course we had no clue about trip curves or coordination, nor about costs. We were just 'bs'ing about what would be 'best.

I guess such a system could be built with DIN mount breakers and fuse holders.

Jon

 

[Jraef]

There has been a change in the UL listing for VFDs, they have removed them from UL-508C and now require listing under UL-61800-5-1 in order to align with IEC requirements. As part of this, all VFDs will now need high speed fuses, even if you have breakers. So most drive mfrs are doing just that; sizing the fuses to where the breaker (or drive) will trip first, then the fuses only clear if the short circuit current is higher and faster than the breaker can react to.