it and not less than the voltage applied to other conductors or busbars with which it may come in contact.
408.20 Location of Switchboards. Switchboards that have any exposed live parts shall be located in permanently dry locations and then only where under competent super- vision and accessible only to qualified persons. Switchboards shall be located such that the probability of damage from equipment or processes is reduced to a minimum.
408.22 Grounding of Instruments, Relays, Meters, and Instrument Transformers on Switchboards. Instruments, relays, meters, and instrument transformers located on switchboards shall be grounded as specified in
250.170 through 250.178.
III. Panelboards
408.30 General. All panelboards shall have a rating not less than the minimum feeder capacity required for the load calculated in accordance with Parts n, III, IV, or V of Article
220 as applicable.
FPN: See 110.22 for additional requirements.
408.36 Overcurrent Protection. In addition to the requirement of 408.30, a panelboard shall be protected by an overcurrent protective device having a rating not greater than that of the panelboard. This overcurrent protective device shall be located within or at any point on the supply side of the panelboard.
Exception No. 1: Individual protection shall not be required for a panelboard used as service equipment with multiple disconnecting means in accordance with 230.71. In panelboards protected by three or more main circuit breakers or sets of fuses, the circuit breakers or sets of fuses shall not supply a second bus structure within the same panelboard assembly.
Exception No. 2: Individual protection shall not be required for a panelboard protected on its supply side by two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panelboard. A panelboard constructed or wired under this exception shall not contain more than 42 overcurrent devices. For the purposes of determining the maximum of 42 overcurrent devices, a 2-pole or a 3-pole circuit breaker shall be considered as two or three overcurrent devices, respectively.
Exception No. 3: For existing panelboards, individual protection shall not be required for a panelboard used as service equipment for an individual residential occupancy.
(A) Snap Switches Rated at 30 Amperes or Less. Panel-boards equipped with snap switches rated at 30 amperes or less shall have overcurrent protection of 200 amperes or less.
(B) Supplied Through a Transformer. Where a panel-
board is supplied through a transformer, the overcurrent
protection required by 408.36 shall be located on the sec ondary side of the transformer.
Exception: A panelboard supplied by the secondary side of a transformer shall be considered as protected by the over-current protection provided on the primary side of the transformer where that protection is in accordance with 240.21(C)(1).
(C) Delta Breakers. A 3-phase disconnect or overcurrent device shall not be connected to the bus of any panelboard that has less than 3- phase buses. Delta breakers shall not be installed in panelboards.
(D) Back-Fed Devices. Plug-in-type overcurrent protection devices or plug-in type main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in