the overcurrent protective devices shall not be less than 50 percent of the momentary rating or 100 percent of the long-time rating, whichever is greater.
(B) Feeder Conductors. The rated ampacity of conductors and overcurrent devices of a feeder for two or more branch circuits supplying X-ray units shall not be less than 100 percent of the momentary demand rating [as determined by 660.6(A)] of the two largest X-ray apparatus plus 20 percent of the momentary ratings of other X-ray apparatus.
FPN: The minimum conductor size for branch and feeder circuits is also governed by voltage regulation requirements. For a specific installation, the manufacturer usually specifies minimum distribution transformer and conductor sizes, rating of disconnect means, and overcurrent protection.
660.7 Wiring Terminals. X-ray equipment not provided with a permanently attached cord or cord set shall be provided with suitable wiring terminals or leads for the connection of power-supply conductors of the size required by the rating of the branch circuit for the equipment.
660.8 Number of Conductors in Raceway. The number of control circuit conductors installed in a raceway shall be determined in accordance with 300.17.
660.9 Minimum Size of Conductors. Size 18 AWG or 16
AWG fixture wires, as specified in 725.49, and flexible
cords shall be permitted for the control and operating
circuits of X-ray and auxiliary equipment where
protected by not larger than 20-ampere overcurrent
devices.
660.10 Equipment Installations. All equipment for new X-ray installations and all used or reconditioned X-ray equipment moved to and reinstalled at a new location shall be of an approved type.
II. Control
660.20 Fixed and Stationary Equipment.
(A) Separate Control Device. A separate control device, in addition to the disconnecting means, shall be incorporated in the X-ray control supply or in the primary circuit to the high-voltage transformer. This device shall be a part of the X-ray equipment but shall be permitted in a separate enclosure immediately adjacent to the X-ray control unit.
(B) Protective Device. A protective device, which shall be permitted to be incorporated into the separate control de-vice, shall be provided to control the load resulting from failures in the high-voltage circuit.
660.21 Portable and Mobile Equipment. Portable and mobile equipment shall comply with 660.20, but the manually controlled device shall be located in or on the equipment.
660.23 Industrial and Commercial Laboratory
Equipment.
(A) Radiographic and Fluoroscopic Types. All radio- graphic- and fluoroscopic-type equipment shall be effectively enclosed or shall have interlocks that de- energize the equipment automatically to prevent ready access to live current-carrying parts.
(B) Diffraction and Irradiation Types. Diffraction- and irradiation-type equipment or installations not effectively enclosed or not provided with interlocks to prevent access to live current-carrying parts during operation shall be provided with a positive means to indicate when they are energized. The indicator shall be
a pilot light, readable meter deflection, or equivalent means.