CSLB C-46 Solar ContractorPhotovoltaic System InstallationMedium
A solar installer is connecting a new grid-tied string inverter to a residential service panel. According to NEC 690.8(A)(1), the inverter's maximum continuous output current is 28 Amperes. What is the minimum required ampacity for the conductors connecting the inverter's AC output to its overcurrent protective device?
- A30 Amperes
- B40 Amperes
- C35 Amperes
- D28 Amperes
Show answer & explanationAnswer & explanation
Correct answer: C. 35 Amperes
NEC 690.8(A)(1) requires that the ampacity of conductors for PV inverter output circuits be at least 125% of the maximum continuous current. For a 28A continuous output, the calculation is 28A * 1.25 = 35A. Therefore, the conductors must have a minimum ampacity of 35 Amperes.
Why the other options are wrong
- A. 30A is too low and does not meet the 125% rule.
- B. 40A would also be acceptable, but 35A is the minimum required.
- D. 28A is the continuous current, not the ampacity required by the 125% rule.
NEC 690.8(A)(1) Conductor Sizing
Conductors for PV inverter output circuits must have an ampacity of not less than 125% of the maximum continuous current of the inverter output circuit.
- Applies to AC output conductors.
- Accounts for continuous load conditions.
- Ensures conductor safety and prevents overheating.
Memory trick: Continuous current needs a 25% safety boost for wire size.