How to Rate Electric Service Boxes

Look at the service box for its printed capacity and suitable wire types. The capacity is a number followed by "amps" and the wire type may be listed as copper (Cu) or aluminum (Al).

Look at the printed amps on the main breaker. This number must be less than the capacity of the service box for a safe system.

Look at the printed wire type on the service wires entering the box. If "AL" is printing on the cable's sheathing, the box also needs to be rated for aluminum. Aluminum wire is commonly used as service entrance wires because of its lower cost. Determining the wire type may be difficult if it is not printed on the cable. Hire an electrician to open the box and confirm the wire type if it's not printed on the cable.