Equipment & Systems

Each service must have a readily accessible disconnect to shut off all ungrounded service conductors; typically limited to no more than six switches or breakers grouped together.

Service-entrance conductors are sized for the calculated service load and must have ampacity not less than the service rating.

A panelboard must be protected by an overcurrent device rated no greater than the panelboard's busbar rating.

Modern lighting and appliance panelboards may contain any number of overcurrent devices up to the panel's listed rating (the old 42-circuit limit was removed).

Protects conductors and equipment by opening the circuit on overload or short-circuit/ground-fault before damage occurs.

An overload is current above rating in an otherwise sound circuit; a short circuit is an abnormal low-impedance fault between conductors.