Nec Ocpd Ratings: 450.3(A)
fuse supervised high z 300A to fuse unsupervised 250A
NEC overcurrent protective device (OCPD) ratings — standard ampere ratings for fuses and circuit breakers per Section 240.6(A), motor branch circuit protection per 430.52(C)(1), overload relay sizing per 430.32, and transformer OCPD sizing per 450.3
| nec section | record id | description | device type | location type | rating amp (A) | secondary protection pct | standard | transformer impedance pct max |
|---|---|---|---|---|---|---|---|---|
| 450.3(A) | fuse supervised high z 300A | Transformer primary OCPD — % of primary rated current | fuse | — | 300 | 300 | NEC (NFPA 70) Table 450.3(A) | supervised high z |
| 450.3(A) | fuse supervised with secondary fuse 250A | Transformer primary OCPD with secondary protection — % of primary rated current | fuse | 250 | 250 | 250 | NEC (NFPA 70) Table 450.3(A) | supervised with secondary fuse |
| 450.3(A) | fuse unsupervised 250A | Transformer primary OCPD — unsupervised location — % of primary rated current | fuse | 125 | 250 | 250 | NEC (NFPA 70) Table 450.3(A) | unsupervised |
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