Q. What is the maximum number of overcurrent devices permitted in a lighting and appliance branch-circuit panelboard? What is the maximum number of overcurrent devices permitted in a power distribution unit (PDU) of an information technology system?

A) 36 / 42
B) 42 / 42
C) 54 / 42
D) 54 / 54

Answer: B

Explanation: Section 408.35 of the 2005 NEC permits a maximum of 42 overcurrent devices (other than those for mains) to be installed in a lighting and appliance branch-circuit panelboard. A change to Section 645.17 now permits an unlimited number of panelboards (i.e., multiple panelboards) to be installed in a single cabinet. However, each panelboard may have no more than 42 overcurrent devices installed in it. And this change is limited to power distribution units (PDUs) installed as part of an information technology system.

Owen is the owner and president of National Code Seminars and the holder of master electrician certifications in 46 states. He can be reached at necexpert@aol.com.