Practice Questions: OCP Sizing
Real questions from our bank, all referenced to NEC 2026. Tap “Show explanation” after you answer.
A continuous load of 36 amperes is supplied by a branch circuit. Per NEC 210.20(A), the overcurrent protective device must be rated at not less than what value?
- A36 amperes
- B40 amperes
- C45 amperes
- D50 amperes
Show explanation
For continuous loads, OCPD must be rated ≥125% of load: 36A × 1.25 = 45A. Next standard size per 240.6(A) is 45A.
A non-continuous load is 28 amperes and a continuous load is 20 amperes on the same circuit. What is the minimum calculated overcurrent device rating per NEC 210.20(A)?
- A48 amperes
- B50 amperes
- C53 amperes
- D60 amperes
Show explanation
OCPD rating = (20A × 1.25) + 28A = 25 + 28 = 53A minimum calculated. Next standard size per 240.6(A) is 60A.
What is the standard OCPD rating that is immediately larger than a calculated load current of 47 amperes?
- A45 A
- B50 A
- C60 A
- D70 A
Show explanation
Per NEC 240.6(A), the standard OCPD ratings are: 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, etc. A calculated load of 47 A does not match a standard size, so per 240.4(B), the next standard size above 47 A is 50 A.
A feeder calculation results in 182 amperes. What is the correct standard OCPD rating to select?
- A175 A
- B200 A
- C225 A
- D250 A
Show explanation
Per NEC 240.6(A), standard OCPD ratings include 175, 200, 225, 250, etc. The calculated current of 182 A is between 175 A and 200 A. Per 240.4(B), the next standard size up is 200 A.
A calculated circuit load is 38 amperes. Per Table 240.6(A), which standard OCPD size should be selected?
- A35 A
- B40 A
- C45 A
- D50 A
Show explanation
Per NEC 240.6(A), standard sizes include 35 A, 40 A, 45 A, 50 A. A calculated load of 38 A falls between 35 A and 40 A. Per 240.4(B), the next standard size above the calculated load is 40 A.
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