CSLB C-46 Solar ContractorPhotovoltaic System InstallationMedium
A solar installer is connecting a new grid-tied string inverter to a residential service panel. The inverter has a maximum continuous output current of 28A at 240V. According to NEC 690.8(A)(1), what is the minimum required ampacity for the conductors connecting the inverter to the overcurrent protection device (OCPD)?
- A40A
- B35A
- C50A
- D28A
Show answer & explanationAnswer & explanation
Correct answer: B. 35A
NEC 690.8(A)(1) requires that PV system circuit conductors be sized to carry a minimum of 125% of the maximum continuous current. For a 28A continuous current, the minimum ampacity is 28A * 1.25 = 35A.
Why the other options are wrong
- A. This value is higher than required by the 125% rule, potentially leading to unnecessary cost or oversized conductors.
- C. This value is significantly higher than required by the 125% rule, indicating a misapplication of the NEC.
- D. This is the continuous current, not the minimum required ampacity after applying the 125% multiplier.
NEC 690.8(A)(1) Conductor Sizing
NEC 690.8(A)(1) mandates that PV system circuit conductors must be sized to carry a minimum of 125% of the maximum continuous current to account for potential sustained loads.
- Applies to PV system circuit conductors (DC and AC).
- Calculated as 125% of the maximum continuous current.
- Ensures conductors can handle sustained operational currents without overheating.
Memory trick: Always Multiply Current by 1.25 for PV Conductors.