Services & DistributionQuestion 47 of 521
For a transformer over 1000 V or with primary-only protection under 450.3(B), where primary current is 9 A or more, the primary OCPD generally may not exceed what percentage of primary full-load current?
a.125%
b.300%
c.167%
d.250%
Explanation
Table 450.3(B) permits primary-only protection at not more than 125% of rated primary current when that current is 9 A or more. 167%/250%/300% apply to higher-current or combined primary-and-secondary arrangements, not the basic 125% primary-only case.
Law Reference: 2023 NEC §450.3(B)Practice all 521 questions free — no signup required.
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