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What is the proper application of NEC Article 110.14(C)(1)(b)? 110.14(C)(1)(b) reads as follows: "Termination provisions of equipment for circuits rated for over 100 amperes, or marked for conductors greater than 1 AWG, shall be used only for one of the following:" The "or" in this article yields two greatly different results. Based on the first part any device of 100 ampere (110 amps) we use the 75 degree column in Table 310.15 (B) and 2 AWG is sufficient, but the "or" part of the statement requires a 1/0 AWG conductor before we use the 75 degree column in Table 310.15 (B). Under the "or" part of the rule for a 110 amp device we use a 1 AWG under the 60 degree column of Table 310.15(B) and we need to use 1/0 AWG for 125 amp devices; since #1/0 AWG is rated for 125 amperes at 60 degrees C and 1 AWG cannot be rated used for the 75 degrees C. Any clarification on this article is appreciated. Thanks Rick
Hey Rick thanks for your question, the wording could be improved. The termination device is often part of the equipment such as the terminals of a circuit breaker of fusible switch. If that circuit breaker or fusible switch is rated more than 100 amperes then the temperature rating is 75 degrees C unless listed and marked otherwise. If the termination device does not have an ampere rating then if marked for conductors larger than 1 AWG its temperature rating is 75 degrees C unless listed and marked otherwise.
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