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#103475 - 08/29/02 08:28 AM Will These Devices Recognize an Arc Fault?
Joe Tedesco Offline
Member

Registered: 10/07/00
Posts: 3325
Loc: Boston, Massachusetts USA


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.
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#103476 - 08/29/02 09:57 AM Re: Will These Devices Recognize an Arc Fault?
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
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
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#103477 - 08/29/02 11:23 AM Re: Will These Devices Recognize an Arc Fault?
Joe Tedesco Offline
Member

Registered: 10/07/00
Posts: 3325
Loc: Boston, Massachusetts USA
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.
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#103478 - 08/29/02 12:16 PM Re: Will These Devices Recognize an Arc Fault?
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
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
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#103479 - 08/29/02 01:01 PM Re: Will These Devices Recognize an Arc Fault?
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
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.

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#103480 - 08/29/02 01:24 PM Re: Will These Devices Recognize an Arc Fault?
Creighton Offline
Member

Registered: 01/06/02
Posts: 56
Loc: Hayward, CA
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

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#103481 - 08/29/02 02:56 PM Re: Will These Devices Recognize an Arc Fault?
Joe Tedesco Offline
Member

Registered: 10/07/00
Posts: 3325
Loc: Boston, Massachusetts USA
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.

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Joe Tedesco, NEC Consultant

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#103482 - 08/29/02 03:47 PM Re: Will These Devices Recognize an Arc Fault?
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
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.

 Quote:
1. Will these devices recognize an arc fault?


subject to definition....


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


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).]

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#103483 - 08/29/02 04:17 PM Re: Will These Devices Recognize an Arc Fault?
Joe Tedesco Offline
Member

Registered: 10/07/00
Posts: 3325
Loc: Boston, Massachusetts USA

Photo Courtesy: codecheck.com

It this what you are talking about?

Will these OCPD's operate when necessary?
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Joe Tedesco, NEC Consultant

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#103484 - 08/29/02 04:58 PM Re: Will These Devices Recognize an Arc Fault?
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
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 .....

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