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- 310.12 (A) Services part. This is the NEC 83% rule for wire ampacity that states “… shall be permitted to have an ampacity not less than 83 percent of the service rating.” This simply means that we can use a smaller wire if it can carry at least 83% of the amp load.
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According to the 83% NEC rule, a wire for 100 amp service has to handle at least 83 amps (have at least an 83A ampacity). That means that we don’t have to use the 4 AWG wire; we can use the 3 AWG wire because it has 85A ampacity which is higher than the 83A required ampacity.
Oct 30, 2021 · #1. 310.15 B7 states that you can put 2/0 (rated for 175 amps) on 200 amp breaker using the 83% rule. If your load calculation is 190 amps based on NEC 220 can 2/0 still be used or does NEC 215.2 A apply? infinity. Moderator. Staff member. Location. New Jersey. Occupation. Journeyman Electrician. Oct 30, 2021. #2.
Jul 6, 2020 · All the 83% rule does is allow you to use an 83 amp conductor with 100 amp overcurrent protection in specific situations (or whatever value is 83 percent for other than 100 amp overcurrent device). When they took the table away a few years back they wanted us to apply ampacity adjustments before coming up with a final conductor size, the old ...
Feb 19, 2023 · We are allowed to use the 83% rule because it is a residential service or feeder. The 200 ampere service rating is multiplied by the 83% ( 200 X 83% = 166. amperes) which gives us 166 amperes.
Jul 25, 2020 · Each 200A dwelling unit, is what could be served by just 166A of conductor ampacity, according to the 83% rule, and still be allowed to be protected by the 200A service breaker. The 83% rule would not be allowed to apply for either the 800A collective service conductors, or the 200A house loads service, because neither of these circuits feed ...
Jul 10, 2023 · The National Electrical Code (NEC) provides ampacity tables to help users select the appropriate wire size for their installation based on the wire’s current-carrying capacity. Specifically, table NEC 310.16 lists the minimum ampacity and size for various types of conductors in different insulation temperatures and voltage ratings.
