systems shall be grounded by
connection to the equipment grounding conductor of
the supply branch circuit(s) or feeder using the types of
equipment grounding conductors specified in 250.118.
Exception: Portable cord-connected signs shall not be required to be connected to the equipment grounding conductor where protected by a system of double insulation or its equivalent. Double insulated equipment shall be distinctively marked.
(2) Size of Equipment Grounding Conductor. The equipment grounding conductor size shall be in accordance with 250.122 based on the rating of the overcurrent device protecting the branch circuit or feeder conductors supplying the sign or equipment.
(3) Connections. Equipment grounding conductor connections shall be made in accordance with 250.130 and in a method specified in 250.8.
(4) Auxiliary Grounding Electrode. Auxiliary grounding electrode(s) shall be permitted for electric signs and outline lighting systems covered by this article and shall meet the requirements of 250.54.
(5) Metal Building Parts. Metal parts of a building shall not be permitted as a secondary return conductor or an equipment grounding conductor.
(B) Bonding.
(1) Bonding of Metal Parts. Metal parts and equipment of signs and outline lighting systems shall be bonded together and to the associated transformer or power- supply equipment grounding conductor of the branch circuit or feeder supplying the sign or outline lighting system and shall meet the requirements of 250.90.
(2) Bonding Connections. Bonding connections shall be made in accordance with 250.8.
(3) Metal Building Parts. Metal parts of a building shall not be permitted to be used as a means for bonding metal parts and equipment of signs or outline lighting systems together or to the transformer or power- supply equipment grounding conductor of the supply circuit
(4) Flexible Metal Conduit Length. Listed flexible metal conduit or listed liquidtight flexible metal conduit that encloses the secondary circuit conductor from a transformer or power supply for use with neon tubing shall be permitted as a bonding means if the total accumulative length of the conduit in the secondary circuit does not exceed 30 m (100 ft).
(5) Small Metal Parts. Small metal parts not exceeding
50 mm (2 in.) in any dimension, not likely to be energized, and spaced at least 19 mm ( 3/4 in.) from neon tubing, shall not require bonding.
(6) Nonmetallic Conduit Where listed nonmetallic con- duit is used to enclose the secondary circuit conductor from a transformer or power supply and a bonding conductor is required, the bonding conductor shall be
installed separate and remote from the nonmetallic conduit and be spaced at least 38 mm (l'/i in.) from the conduit when the circuit is operated at 100 Hz or less or
45 mm (1% in.) when the circuit is operated at over 100
Hz.
(7) Bonding Conductors. Bonding conductors shall comply with (a) and (b).
(a) Bonding conductors shall be copper and not smaller than 14 AWG.
(b) Bonding conductors installed externally of a sign or raceway shall be protected from physical damage.