1. Will these devices recognize an arc fault?

2. Are these devices considered as a reliable method for clearing an "overcurrent condition or overload," as defined in Article 100 in the NEC?

As this area is sometimes used as a reference for Vocational studies we request that comments be kept to the subject as much as possible.

Thank You for your cooperation in this matter.

The item on the left will not clear any faults as it is only a mechanical adapter. I'm not sure what the device on the right is. The other 2 are fuses and will clear overcurrents and overloads based on their rating.
Are you trying to tell us that fuses are not a reliable method of clearing overloads and overcurrents? Have you ever found a breaker that wouldn't trip? How about a fuse that wouldn't blow? In my opinion a fuse is a more reliable OCPD than the thermal magnetic device that we normally use. Are they subject to tampering? Sure, but with so many breakers being of the plug in type, they both are too often replaced with one of a size larger than permitted by the code. The type S adapter makes it harder to tamper with a type S fuse than it is to tamper with a circuit breaker.
As far as clearing an arc fault, they will only do this if and when the current produces enough heat to exceed the melt point of the fuse element.
Don

Don:

Answers to

Your question 1. No
Your question 2. Yes
Your question 3. No, never have.

Please expand on your experiences with circuit breakers. If possible, please include code references and edition used.

Joe,
I don't know how to cite a code reference for a mechcanical device failing to operate. It is not very common, for a breaker to fail to open. Many times breakers are falsely blamed, when it was really the impedance of the fault return path that kept the breaker from opening. If the impedance of the fault path limits the current, the breaker may never clear the fault. This, of course, also happens with fuse circuits. However, there are some cases where the breaker doesn't open the circuit when it should. This sometimes happens where breakers are installed where there is enough dampness to cause internal corrosion. This corrosion can in some cases prevent the trip lever from moving and opening the circuit. Some experts recommend opening and closing the breaker at least every six months to help prevent this from happening. I'm not sure if that really helps as manually opening and closing the breaker does not move the trip lever.
Note that the NEC does not permit the use of edison based fuses in new installations. See 240.52 in the '02 NEC. They are permited to be used for replacement applications only, if there is no evidence of previous overfusing or tampering. 240.51(B). You would be permited to install a plug fuse panel in a new installation as long as you installed Type S adpaters in the edison bases at the time of installation. 240.52 The device on the left of the picture is a Type S adapter.
Don

I believe the center two items will consistently clear arcing faults—within their design parameters, lacking promises or hints of “may…” anything. Over time, they have operated more reliably and accurately than any equally aged electromechanical equivalent. They were among essentially the first standardized overcurrent devices that allowed virtually everyone to use electricity on a daily basis without turning a family’s possessions into a pile of carbon. It’s fair to say they could be considered the original plain-vanilla 10kA-interrupting solid-state protective device.

Although a bit dated, but still having a UL guide-card category, in its time, the righthand device bordered on a discount-store get-rich-quick scheme.

Step 2: To what ANSI/NRTL standard(s) are the various magical plug-in testers listed and labeled? Do increasingly yellow “home inspectors” ever have certificates of NIST-originated traceability for their clever little boxes?

Reference: UL White book and corporate memory.

Around 1950 I was working in an office on VanNess Avenue in San Francisco. Needed to extend a receptacle circuit. The office was too busy for me to start trying circuits to kill the one I wanted to work on, so I removed the receptacle closest to where I wanted to extend the circuit, held the two wires together and touched them together to open the breaker. The breaker never opened, and the wires got so hot I could not keep holding them.
On the other hand I have never known a fuse to not open when it was called upon to do so.
That was only one incident, but it was enough to kill my faith in circuit breakers.
The item on the right is a circuit breaker built into an edison base holder. They were UL labeled, and sold by Sears. Have not seen one in a long time, and have no opinion as to their worth.
Creighton

Electricians and inspectors should be aware of this “fuse adapter removal tool.”

If the steel wire on the outside of the adapter was removed, the adapter could be easily removed.

Removal of the steel wire will allow a larger adapter, so a larger fuse could be installed.

all the pictured devices live in abundance here in Vermont.

for show & tell i have an old refurbished main range & 4 in my shed, with the 'mini-breakers' shown far left.


subject to definition....



one good Q deserves another.....

why is it fused disco's ,MCC, etc are sometimes desired above breakers in industry?

[This message has been edited by sparky (edited 08-29-2002).]

Photo Courtesy: codecheck.com

It this what you are talking about?

Will these OCPD's operate when necessary?

yes Joe,
that is what i have in my shed, with exception to that green 30 there....

fuses, in my opinion only, are of overall simpler design and thus fail less than breakers in many similar situations i see every day.

they have gone by the wayside residentially due to thier inconvienence...

if you check some larger service entrance disco's you'll find that a higher AIC rating can be had for fewer $$$

thus, fuses are still being used, residentially .....

I've seen a couple of these on my travels, but never had a chance to look into them more closely.

What type of fuses are used in the main & range pull-outs? Cartridge?

How were the circuits fed from the Edison-base fuses -- Two small appliance plus two general illumination? Or do these pre-date the NEC requirement for two small appliance kitchen circuits?

yes Paul, cartridge fuses, if you look close at the pullout it has 4 round spots, sort of a circle in a circle.

This holds the 2 fuse clips on each side, the screws where then filled with a rubbery substance.

Said substance will many times be seen to burn off , due to years of constant loading, and four 30 A (green colored) fuses

An observance i've commonly pointed out to justify an upgrade.


pre-date many requirements, but many are still in service here. 30A fuses....K&T wiring....we got it all!

The mini-breakers (pictured on the right in Joe's first photo) are still manufactured and sold. As to their reliability, as a child I lived in a run-down third-storey walkup where all the outlets and lights were controlled by a single fuse (replaced by a 15-amp minibreaker).

The thing was pretty reliable and it always "popped" when we had too many high-amperage things plugged in at once. Of course, I can't speak for other people's houses.

What I do remember is that the buttons are hard to press (which could be an issue with people with arthritic hands).

The hospital where I used to work had mini-breakers in the original building(circa 1933). They worked well and would detect arc faults, cut cords and faulty eqipment. They were also a bear when we turned on the window A/C units. We finally wrecked them out in 1995 when the wing was remodeled.

In regards to the question about detection of arcing faults with these devices. The "plug" fuses will detect arcing faults if the magnitude of the arcing fault is sufficient (see the time-current curves for the device). The problem is that often arcing faults are not high enough to trip the overcurrent device. The AFCI will detect and clear more arcing faults than a similar size fuse or cb, but it is NOT the total solution and will not detect all arcing faults. It is an improvement in the right direction, but other protection methods should also be explored.

In regards to reliability, "plug" fuses are reliable when properly applied. I think the reason we have gotten away from fuse panels in the residential market is because of two things. One, at one time there was a quality issue with the construction of the fuse panels. Two, people do not like to replace fuses in this type of application. I really don't think people went to circuit breakers becuase it was a better protective device.

There was a good point about the reliability of overcurrent protective devices. This is often more of an issue in commercial and industrial applications. In these applications one must realize that circuit breakers, since they are mechanical devices must be maintained and tested to assure proper application and operation. See NFPA 70B, NEMA AB-4 and manufacturers literature. The reliability of this device can be adversely affected if these procedures are not followed. We have a presentation on testing and maintenance on our website at www.bussmann.com (go to services then on-line training. Clive Kimblin of Cutler-Hammer also mentioned this in a recent article of the IAEI Magazine (March/April 2002).

Fuses on the other-hand are not a mechanical device, do not require maintenance and testing (although the switch will require maintenance and inspection), give consistant operation regardless of age, and thus are often considered more reliable devices.

I am a firm believer in the replacing of fuses with the fuse-shaped circuit breaker pictured on the right- though, as I read the code, their use is not allowed.
I say "not allowed," as the code calls for smaller plug fuses to be replaces with type "S" tamper-resistant fuses. I believe that this was an oversight by the code panels.
I like circuit breakers because the reset feature makes it less likely that they will be replaced willy-nilly with larger sizes. Why go to the hardware store when all you need to do is push a button, then refrain from using the hot plate and the microwave at the same time?

I believe you could use the circuit breaker style Edison base type device if you met the requirements of of 240.51(B) and the circuit breaker style Edision base device was a listed product. 240.51(B) permits plug fuses of the Edison base type for replacement in existing installations where there is no evidence of overfusing or tampering. I know 240.51(B) refers to a Edison base type plug fuse but if it is a circuit breaker edision base device that is listed I don't think anyone would give you a problem. Proposal time is up November 1, you could always submit a proposal to better define this capability.

breakers that dont work......didnt federal pacific go bust..........

The item on the far right, to my knowledge, is a cheap conversion from fuses to circuit breakers. I've had one before. dunno if those really work.

I see that there's a use for us old timers...:-)

The device on the right, while manufactured by Mechanical Products, is distributed by Cooper/Bussman. It is UL-listed, and has to pass exactly the same tests as any other circuit breaker.

For those who are unfamiliar with the old-time fuse boxes, they were still commonly used in residential construction into the mid-'60's. Of course, they were made in larger forms than the "4+2" shown.

I have such a panel on my house. The circuits divide as follow:
- One cartridge fuse holder has a pair of NON-60 fuses, and is the main disconnect;
- One cartridge fuseholder in not used, as I have a gas stove;
- One 15 amp plug fuse feeds one side of the house, lights and receps both;
- Another feeds the other side of the house;
- A third, fused at 20 amps, is for the electric space heater in the bathroom (primary heat is gas, no fan);
- And the fourth is for an outside receptacle I've added.
( I've used the term "fused" freely....I actually have those little CB's installed).

This house was built in 1940, and wired with an early form of Romex...Cloth wrapper, no ground wire. Apart from the water bond, there is no grounding. All receptacles are two-prong. The only bath recep is part of the light over the mirror. The main room, with almost fifty feet of perimeter, has exactly one receptacle. The only kitchen receptacle shares a single-gang box with a switch for the exhaust fan.