How Does Temperature Rating Impact Conductor Size Selection

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The Answer is Another factor that must be taken into consideration when determining the conductor size is the temperature rating of the devices and terminals. The conductor will be selected and coordinated so as to not exceed the lowest temperature rating of any connected termination, any connected conductor, or any connected device. This means that regardless of the temperature rating of the conductor, the allowable ampacity must be selected from a column that does not exceed the temperature rating of the terminations. The conductors listed in the first column of NEC Table
310.16 have a temperature rating of 60 degrees C (140 degrees F), the conductors in the second column have a rating of 75 degrees C (167 degrees F), and the conductors in the third column have a rating of 90 degrees C (194 degrees F). The temperature ratings of devices such as circuit breakers, fuses, and terminals are found in UL product directories. The temperature rating may be found on the piece of equipment. As a general rule, the temperature rating of devices will not exceed 75 degrees C (167 degrees F).

How Does Temperature Rating Impact Conductor Size Selection

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