W-C-375-SUP-2 Circuit Breakers, Molded Case; Branch Circuit and ServiceThis specification covers the general requirements and test procedures for molded case circuit breakers which fall within the general parameters specified in table XVI which are specifically designed to provide service-entrance, feeder, meter-service, or branch circuit protection and rated at not more than 4,000 amperes and 600 volts ac, 60 hertz Hz see 3.1 and 6.1.

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W-C-375E

TABLE XVI.  Classification of ratings - Continued.

11  Interrupting ratings are not limited to the values or groups of values listed, however, the values listed are minimum values for the class specified.

21  Single-unit or duplex construction must be specified.

31  This class may incorporate a current limited device within the breaker case.

41  Use minimum frame size for ampere rating.

6.6  Warning.  Potentially hazardous situations are inherent in some of the test procedures specified in this specification.  Precautions should therefore be taken to insure that test personnel are adequately protected and observe the necessary safety measures at all times.

6.7  Definitions.

6.7.1  Tripping time.  Tripping time is the total interval of elapsed time from the instant of applying a given overcurrent to the circuit breaker to the completion of the interruption of the circuit.

6.7.2  "O" and "CO" operation.  The "O" and "CO" operations are defined as "O" closing the short circuit on the closed circuit breaker and "CO" closing the circuit breaker on the short circuit.

6.7.3  Stabilize.  The temperature of a device is considered to be stable when three successive temperature readings taken at not less than 10 minute nor more than 20 minute intervals indicate no temperature change.

6.7.4  Ambient temperature.  Ambient temperature is considered to be the temperature of the air surrounding the device under test.  Measurements shall be taken by thermocouple or thermometers placed not more than 12 inches from and in a plane horizontal to the center of the device under test.

6.7.5  Independent trip.  A multi-pole circuit breaker so designed that one pole trips independently of the other.

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