Calculate the total current of all electrical equipment. that want to be connected to the breaker The sum of the calculated current should not exceed 80% of the breaker capacity. For example, a 15 A breaker can be connected to external devices up to 12A (15 x 0.80 = 12), and a 20 A breaker can be connected to external devices up to 16A (20 x 0.80 = 16). This can lead to calculation errors and can cause a fire.