Governing Standards

You will recall from Module 5 that circuit breakers are designed, built and tested in accordance with one or more specific sets of standards. In this module, you will be introduced to the standards specific to low voltage power circuit breakers. The intent here is not to present and study the different applicable standards word for word. That type of undertaking would be a course unto itself. Our goal is to understand a little about low voltage power circuit breaker related standards, where they were, and where they are today.



You will hear many people repeat specific standards designations. Many of those same people do not have an intimate knowledge of what the standards actually say, nor are we saying they should. The actual product selection based on standards compliance should be left to the experts. It is helpful, however, to know what specific standards your products comply with and what general topic a specific standard addresses.

Keep in mind that a standard exists for almost everything. There are specific standards for circuit breakers and others for the structural assembly. Compliance with these exacting standards ensures customers of the very best possible product selection with a high degree of comfort. There is no room for compromise when performance, quality and safety are involved.
A number of years ago, low voltage power circuit breakers and most other types of equipment were designed and built primarily with only domestic standards in mind. This approach also was taken by foreign suppliers. A manufacturer would offer a circuit breaker designed, tested and manufactured in keeping with applicable standards for that part of the world or even particular country. Trying to play a significant role in other world markets was, at best, extremely difficult. If manufacturers today expect to be global participants, they must offer products that comply with the standards applicable to a variety of different markets around the world. This will require that you become familiar with both domestic and international nomenclature, ratings, procedures and governing standards. The task is greater, but so is the reward.
Some of the lines separating different types of low voltage circuit breakers were at times blurred in the past. Low voltage metal-frame power circuit breakers were built and tested to certain ANSI and UL specifications, while some low voltage encased circuit breakers were tested to UL specifications specific to molded case circuit breakers. The newest low voltage power circuit breakers today, like Magnum DS, are tested to specific low voltage power circuit breaker standards, like ANSI. They are also tested to standards that cover a much broader product scope, like IEC. The primary testing standards associated with low voltage power circuit breakers today are:

ANSI
The American National Standards Institute's ANSI C37.50 is a specific North American testing standard entitled "Low Voltage AC Power Circuit Breakers Used In Enclosures." This standard specifies rigorous tests for product performance. There are additional C37 standards which govern power circuit breaker and trip unit construction, such as C37.13 and C37.17 respectively.

UL
Underwriter's Laboratories Incorporated's UL1066, for the most part, calls for testing to demonstrate compliance with ANSI C37.50 just mentioned. A UL Label is affixed to the breaker to indicate successful compliance.

IEC
The International Electrotechnical Commission IEC 947-2 is a more general international testing standard covering a variety of devices, including circuit breakers of all types, and is entitled "Low Voltage Switchgear and Controlgear."

Closing Comments on Standards
Before concluding this section, it might help to minimize confusion if you remember that there is often a great deal of referencing to other standards that takes place within a specific standard. Successful testing with respect to one standard often includes automatic compliance with other standards.

Example 1 - ANSI C37.13 details the physical attributes, such as stored energy, that a low voltage AC power circuit breaker must have, while ANSI C37.50 references C37.13 and details how the described breaker should be tested. The key here is that successful testing in keeping with ANSI C37.50 brings with it compliance to C37.13.
Example 2 - In a similar fashion, IEC 947-2 references IEC 947-1 (General Rules). Compliance with IEC 947-2, therefore, brings with it IEC 947-1 compliance.