Quick Answer
NEC requirements for solar panel wiring include the use of a maximum of 10 AWG wire for most applications and a minimum of 6 AWG for large systems to prevent overheating and ensure proper energy transfer.
Wire Sizing
The National Electric Code (NEC) requires that wire size be determined by ampacity and distance. According to NEC Article 310, the ampacity of a conductor is its maximum current-carrying capacity. The NEC requires that the ampacity of the conductor be at least 125% of the maximum calculated load current. For example, if the calculated load current is 100 amps, the conductor must have an ampacity of at least 125 amps (100 x 1.25).
Voltage Drop
Voltage drop is a critical consideration in solar panel wiring. According to NEC Article 210, the maximum voltage drop for a conductor is 3% of the system voltage. For example, if the system voltage is 120 volts, the maximum voltage drop is 3.6 volts (120 x 0.03). To determine the acceptable distance between the solar panels and the inverter, we can use an AWG chart to find the maximum distance for a given conductor size.
Wire Sizing Chart
The following chart shows the maximum distance for a given conductor size, assuming a 3% voltage drop:
| AWG | Ampacity | Maximum Distance |
|---|---|---|
| 10 | 30 amps | 100 feet |
| 8 | 40 amps | 150 feet |
| 6 | 55 amps | 225 feet |
| 4 | 70 amps | 300 feet |
| 2 | 85 amps | 375 feet |
Note: These values are for a 120-volt system with a 3% voltage drop. Consult the NEC and local building codes for specific requirements.
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