Services & DistributionQuestion 20 of 521
How many current-carrying conductors can be in a raceway before an adjustment (fill derating) factor must be applied?
a.More than 4
b.More than 3
c.More than 6
d.More than 9
Explanation
Per 310.15(C)(1), adjustment factors apply when there are more than 3 current-carrying conductors in a raceway or cable. The first threshold (4-6 conductors) triggers 80%; the higher counts have their own factors.
Law Reference: 2023 NEC §310.15(C)(1)Practice all 521 questions free — no signup required.
Related questions on this topic
- At the 75 C column of Table 310.16, what is the ampacity of a 1/0 AWG copper conductor?
- A 4/0 AWG copper THHN conductor (90 C, base 260 A) is in an ambient of 45 C. Using the 0.87 correction factor, what is the corrected ampacity?
- Six current-carrying conductors are installed in a single raceway. What adjustment factor applies to their ampacity?
- For equipment terminals on a circuit rated 100 A or less (not marked otherwise), which temperature column must be used to size conductors?
- A feeder supplies a continuous load of 176 A. What minimum conductor ampacity (before derating) is required?
- Six 3 AWG THHN copper conductors (90 C ampacity 110 A) are in one raceway at 30 C ambient. After the fill adjustment, what is the derated ampacity?
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