For an installation with not more than two 2-wire branch circuits, the service disconnecting means shall have a rating of not less than ___ amps.

For an installation with not more than two 2-wire branch circuits, the service disconnecting means shall have a rating of not less than ___ amps.

• A. 20
• B. 30
• C. 60
• D. 100

Answer: (B)

The service disconnect rating is the maximum current the main disconnect can safely interrupt. For a very small installation with not more than two 2-wire branch circuits, the practical minimum size that covers the potential full load is 30 amperes. Two 2-wire branches are typically limited to around 15 A each, so together they can approach 30 A if both are drawing near their limits. Setting the main at 30 A provides adequate headroom to shut off the entire service safely without oversizing the disconnect. Using a smaller rating could lead to nuisance trips or insufficient interruption capacity, while a larger rating isn’t needed for this simple setup. If you had more branch circuits or larger loads, a higher-rated main would be required.

The service disconnect rating is the maximum current the main disconnect can safely interrupt. For a very small installation with not more than two 2-wire branch circuits, the practical minimum size that covers the potential full load is 30 amperes. Two 2-wire branches are typically limited to around 15 A each, so together they can approach 30 A if both are drawing near their limits. Setting the main at 30 A provides adequate headroom to shut off the entire service safely without oversizing the disconnect. Using a smaller rating could lead to nuisance trips or insufficient interruption capacity, while a larger rating isn’t needed for this simple setup. If you had more branch circuits or larger loads, a higher-rated main would be required.