and control transformers, located in or on switchgear or control, shall be connected to an equipment grounding conductor or, where permitted, the grounded conductor.
490.38 Door Stops and Cover Plates. External hinged doors or covers shall be provided with stops to hold them in the open position. Cover plates intended to be removed for inspection of energized parts or wiring shall be equipped with lifting handles and shall not exceed 1.1 m 2 (12 ft 2) in area or 27 kg (60 lb) in weight, unless they are hinged and bolted or locked.
490.39 Gas Discharge from Interrupting Devices. Gas discharged during operating of interrupting devices shall be directed so as not to endanger personnel.
490.40 Inspection Windows. Windows intended for in spection of disconnecting switches or other devices shall be of suitable transparent material.
490.41 Location of Devices.
(A) Control and Instrument Transfer Switch Handles or Pushbuttons. Control and instrument transfer switch
handles or pushbuttons other than those covered in
490.41(B) shall be in a readily accessible location at
an
elevation of not over 2.0 m (78 in.).
Exception: Operating handles requiring more than 23 kg (50 lb) of force shall be located no higher than 1.7 m (66 in.) in either the open or closed position.
(B) Infrequently Operated Devices. Operating handles
for infrequently operated devices, such as drawout fuses, fused potential or control transformers and their primary disconnects, and bus transfer switches, shall be permitted to be located where they are safely operable and serviceable from a portable platform.
490.42 Interlocks — Interrupter Switches. Interrupter switches equipped with stored energy mechanisms shall have mechanical interlocks to prevent access to the switch compartment unless the stored energy mechanism is in the discharged or blocked position.
490.43 Stored Energy for Opening. The stored energy operator shall be permitted to be left in the uncharged position after the switch has been closed if a single movement of the operating handle charges the operator and opens the switch.
490.44 Fused Interrupter Switches.
(A) Supply Terminals. The supply terminals of fused interrupter switches shall be installed at the top of the switch enclosure or, if the terminals are located elsewhere, the equipment shall have barriers installed so as to prevent persons from accidentally contacting energized parts or dropping tools or fuses into energized parts.
(B) Backfeed. Where fuses can be energized by backfeed, a sign shall be placed on the enclosure door identifying this hazard.
(C) Switching Mechanism. The switching mechanism shall be arranged to be operated from a location outside the enclosure where the operator is not exposed to energized parts and shall be arranged to open all ungrounded conductors of the circuit simultaneously with one operation. Switches shall be capable of being locked in the open position. The provisions for locking shall remain in place with or without the lock installed.