How many bolted faults can a residential circuit breaker withstand?

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How many licks does it take to get to the center of a tootsie pop is rather unanswerable. How many faults are they built to withstand and still be functional, should I swap them out after X # of faults, and are they more likely to fail-dangerous if they're old and abused?

According to the UL, a breaker must safely clear its maximum current twice and still be functional. This is a manufacturing standard; not really your concern unless yours broke after the first fault.

CBs are built to always fail-safe. An older breaker that seems to nuisance trip more often than it should might be grounds for replacement and it's probably the easiest way to see if there is something funny going on but there's no reason to arbitrarily replace them after a few faults. Several thousand faults? you'd better check what's going on and that breaker goes in the garbage on principle.

I'm unaware of any UL testing that seeks to show a reset count limit. I'd assume the possibility of a...

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This newsletter was previously sent, this is an updated version.

Electrical Circuit Breakers
Part 1-R

This is the first in a series of articles intended to supplement your knowledge beyond the immediate requirements of the NEC. The series will cover the types of circuit breakers that are found in various types of facilities today. The beginning article lays a foundation (a review for many) and progresses to introducing molded case, insulated case, and drawout types with the series ending with the most advanced of all, microprocessor-based circuit protective devices. The following topics are covered in this the first part of the series:

Circuit Breakers Defined Circuit Breakers As Switches Current Levels To Be Broken Over-Currents Current and Temperature Circuit Breakers As High Temperature Limit Switches Ampacities Of Electrical Conductors Short...
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1

Turn off power supply to the electrical panel. Locate the Service Disconnect or Main circuit breaker in the panel, and set to the "Off" position. This circuit breaker is likely to be the largest value and located either at the top or bottom of the panel. If no such circuit breaker is identified in the panel, it is likely in another panel in the building, or in the meter socket enclosure. Look for other panel(s) to find the circuit breaker needed.

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Inspect the circuit breaker arrangement for unused locations. Pay particular attention to unused spaces at the top and bottom of the cover. Some manufacturers of electrical panels have removable knock outs or plates at these locations, but the panel itself lacks provisions to mount a circuit breaker. Simply stated: Do not rely on the cover alone to determine the ability to add circuits to the panel - check the bus bar.

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Remove the electrical panel cover. Remove fasteners while a helper...

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How to correctly size kA ratings of circuit breakers

Introduction

One of the most important safety aspects to consider when designing an electrical circuit is to correctly size the circuit breaker fault current rating (commonly called the kA rating). Unfortunately many electricians are unaware of this concept, and it remains one of the most common design faults found in electrical circuits. In the last 10 years it has become very common in domestic wiring, because of changes in the way power is distributed to new houses.

So what is the kA rating?

The value of the kA rating determines how much current the circuit breaker can withstand under fault conditions. The circuit breaker only has to withstand this for a brief period of time, usually the time it takes for the circuit breaker to trip. For example, a value of 6kA means that the circuit breaker can withstand 6,000 amps of current during the brief time it takes to trip.

Why is the kA...

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One of the most important safety aspects to consider when designing an electrical circuit is to correctly size the circuit breaker fault current rating (commonly called the kA rating). Unfortunately many electricians are unaware of this concept, and it remains one of the most common design faults found in electrical circuits. In the last 10 years it has become very common in domestic wiring, because of changes in the way power is distributed to new houses.

So what is the kA rating?

The value of the kA rating determines how much current the circuit breaker can withstand under fault conditions. The circuit breaker only has to withstand this for a brief period of time, usually the time it takes for the circuit breaker to trip. For example, a value of 6kA means that the circuit breaker can withstand 6,000 amps of current during the brief time it takes to trip.

Why is the kA rating so important?

Under fault conditions (such as a short circuit) much more...

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Schneider Electric
NT MasterPact Circuit Breaker I think this post is going to be helpful to several of our readers. While the IEC low voltage circuit breaker Standard [IEC 60947-2, Low voltage switchgear and controlgear - Part 2: Circuit-breakers] has been around for many years now, it's surprising how often fault ratings are misunderstood. Hopefully we should be able to clear some of the misunderstanding.

The main parameters

Just to be clear, we are only talking about fault ratings (not rated current). On this, it's probably easiest to start of with the IEC definition of the relevant ratings:

Icu - ultimate short-circuit breaking capacity
a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously

Ics - service short-circuit breaking capacity
a breaking capacity for which the...

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Abstracts from The Credit and Financial Management Review

This quarterly publication, the only professional journal for credit professionals, promotes a comprehensive understanding of credit, A/R and customer financial management in interesting articles written by educators and practitioner experts in their field.

Interested parties, business professionals, academics or graduate students are encouraged to submit material for review and publication in The Credit and Financial Management Review. Please click the Submit Articles in the left frame to contact the editor.

Volume 23, Number 4, 4th Quarter 2017

The Recent Past, Present and Future of Retailing
By: Steven C. Isberg, Ph.D.
The world of retail over the past 40 years has been intensely complex, competitive, disrupted, and therefore, significantly dynamic. Over that time, the pace of change in the general retailing industry has quickened, especially when it comes to consolidation across the...

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