MyCleveland
Senior Member
- Location
- Cleveland, Ohio
Question(s) revolve around 600V building wire R values.
I hope we agree on the fact that a conductor R varies with the conductor temperature.
Two different factors are involved here, ambient temperature and conductor operating temperature.
Please refer to NFPA (NEC) 2020 Chapter 9, Table 9, page 70-706.
This tables Note 1 states “resistance values are valid only at 75C (167F) and for the parameters as given”.
My assumption is that this is stating the conductor operating temperature is 75C, and that the conductor is in fact under load at its MAXIMUM allowable ampacity as taken from NEC Table 310.16 (page 70-161), 75C columns for either CU or AL conductors.
Ques 1: What is the ambient temperature of the cable when these R values were recorded ?
Ques 2: Is Chapter 9, Table 9, Note 1 stating “valid only at 75C”, in fact is stating the conductors are under load at MAXIMUM allowable ampacity per Table 310.16 ?
Ques 3: If question 2 is YES, then if conductors are under a load of a lessor ampacity an adjustment to R is required ?
Please help me in resolving Questions 1-3.
I hope we agree on the fact that a conductor R varies with the conductor temperature.
Two different factors are involved here, ambient temperature and conductor operating temperature.
Please refer to NFPA (NEC) 2020 Chapter 9, Table 9, page 70-706.
This tables Note 1 states “resistance values are valid only at 75C (167F) and for the parameters as given”.
My assumption is that this is stating the conductor operating temperature is 75C, and that the conductor is in fact under load at its MAXIMUM allowable ampacity as taken from NEC Table 310.16 (page 70-161), 75C columns for either CU or AL conductors.
Ques 1: What is the ambient temperature of the cable when these R values were recorded ?
Ques 2: Is Chapter 9, Table 9, Note 1 stating “valid only at 75C”, in fact is stating the conductors are under load at MAXIMUM allowable ampacity per Table 310.16 ?
Ques 3: If question 2 is YES, then if conductors are under a load of a lessor ampacity an adjustment to R is required ?
Please help me in resolving Questions 1-3.