Transformer Sizing & Overcurrent Protection
5:10
A transformer doesn't get protected like a normal conductor — it has its own table.
In this lesson: Table 450.3(B) for transformers 1,000V and below, three full worked examples (10A, 50A primaries), the 125% primary-only rule, how adding secondary protection raises the primary allowance to 250%, the rounding-up rule for non-standard breaker sizes, why inrush current drives these percentages, dry-type vs liquid-filled transformers, and where protection has to be located.
Based on the 2023 NEC (Article 450).
