wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
Today's 2nd PI.
Cheers, Wayne
(A) General.
Ampacities for conductors rated 0 volts to 2000 volts shall be as specified in the Ampacity Table 310.16 through Table 310.21, as modified by 310.15(A) through (F) and 310.12. Under engineering supervision, ampacities of sizes not shown in ampacity tables for conductors meeting the general wiring requirements shall be permitted to be determined by interpolation of the adjacent conductors based on the conductor’s circular-mil area.
The temperature correction and adjustment factors shall be permitted to be applied to the ampacity for the temperature rating of the conductor,if the corrected and adjusted ampacity does but the resulting ampacity may not exceed the ampacity before adjustment and correction factors for the temperature rating of the termination in accordance with 110.14(C).
Statement of Problem and Substantiation for Public Input
This proposal seeks to improve the clarity of meaning of this part of 310.15(A). The current language is open to the following misinterpretation from an overly literal reading:
"First you look up the unadjusted and uncorrected ampacity at the termination temperature rating, call that A. Then you take the tabular ampacity at the insulation temperature rating and apply the adjustment and correction factors, call that B. If B > A, you can't use the insulation temperature tabular ampacity, so you need to apply the adjustment and correction factors to A to get the ampacity."
Since the intention is that the ampacity is just the minimum of A and B, as shown in Annex D Example D3(a) in the section "Ungrounded Feeder Conductors," the proposed language more clearly reflects the intention and precludes the above misinterpretation.
Cheers, Wayne
(A) General.
Ampacities for conductors rated 0 volts to 2000 volts shall be as specified in the Ampacity Table 310.16 through Table 310.21, as modified by 310.15(A) through (F) and 310.12. Under engineering supervision, ampacities of sizes not shown in ampacity tables for conductors meeting the general wiring requirements shall be permitted to be determined by interpolation of the adjacent conductors based on the conductor’s circular-mil area.
The temperature correction and adjustment factors shall be permitted to be applied to the ampacity for the temperature rating of the conductor,
Statement of Problem and Substantiation for Public Input
This proposal seeks to improve the clarity of meaning of this part of 310.15(A). The current language is open to the following misinterpretation from an overly literal reading:
"First you look up the unadjusted and uncorrected ampacity at the termination temperature rating, call that A. Then you take the tabular ampacity at the insulation temperature rating and apply the adjustment and correction factors, call that B. If B > A, you can't use the insulation temperature tabular ampacity, so you need to apply the adjustment and correction factors to A to get the ampacity."
Since the intention is that the ampacity is just the minimum of A and B, as shown in Annex D Example D3(a) in the section "Ungrounded Feeder Conductors," the proposed language more clearly reflects the intention and precludes the above misinterpretation.