Quick Answer
For a solar panel array, a 30-40 amp rating is a suitable range for most small to medium-sized installations. This rating can handle typical 200-500 watt systems with a 12 or 24 volt nominal voltage. However, larger systems may require higher amp ratings.
Determining the Solar Panel Array’s Power Requirements
To determine the necessary amp rating, you need to size the breakers for the maximum current drawn by the system. Start by calculating the system’s maximum DC current, which can be found using the formula: Maximum DC Current (A) = (Total System Power (W) / System Voltage (V)) * Efficiency (as a decimal). For example, a 400-watt system with a 12-volt nominal voltage and 90% efficiency has a maximum DC current of (400 W / 12 V) * 0.9 = 30 A.
Sizing the Solar Breaker
For a 30 A maximum DC current requirement, a 30 A or 20 A breaker is commonly used. This is because the breaker should be sized to handle 125% of the maximum DC current to account for inrush and other system variations. A 20 A breaker would be sufficient, but a 30 A breaker is the recommended minimum to ensure adequate power delivery.
Considering System Voltages and Efficiency
When calculating the maximum DC current, consider the system’s nominal voltage. For a 12-volt system, the calculation is straightforward. However, for a 24-volt system, the calculation will be different due to the higher voltage. Similarly, the system’s efficiency plays a significant role in determining the maximum DC current. A lower efficiency system will require a larger breaker to account for the lost power.
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