What is meant by the term 'Overdutied'?

• A. The equipment's S.C. current rating is greater than the available S.C. current
• B. The S.C. current rating equals the available S.C. current
• C. The equipment's S.C. current rating is less than the available S.C. current
• D. The equipment is rated for continuous double-duty

Answer: (C)

Overdutied means the equipment would have to carry more fault current than it was designed to handle. The short-circuit (S.C.) current rating is the maximum current the equipment can safely withstand during a fault for a specified time. If the available short-circuit current at the point of use is greater than that rating, the equipment is overstressed—i.e., overdutied. So the situation described as the equipment’s S.C. current rating being less than the available S.C. current matches being overdutied. If the rating were equal to or greater than the available current, it would not be overduited. The idea of continuous double-duty isn’t a standard term here.