electronic power supplies other than the following shall have secondary-circuit ground-fault protection:

(1) Transformers with isolated ungrounded secondaries and with a maximum open circuit voltage of 7500 volts or less

(2) Transformers with integral porcelain or glass secondary housing for the neon tubing and requiring no field wiring of the secondary circuit

(C) Voltage. Secondary-circuit voltage shall not exceed

15,000 volts, nominal, under any load condition. The
voltage to ground of any output terminals of the
secondary circuit shall not exceed 7500 volts, under any
load condition.

(D) Rating. Transformers and electronic power supplies shall have a secondary-circuit current rating of not more than 300 mA.

(E) Secondary Connections. Secondary circuit outputs shall not be connected in parallel or in series.
(F) Marking. A transformer or power supply shall be marked to indicate that it has secondary-circuit ground- fault protection.
600.24 Class 2 Power Sources. Signs and outline lighting systems supplied by Class 2 transformers, power supplies, and power sources shall comply with the applicable requirements of Article 600 and 600.24(A), (B), and (C).

(A) Listing. Class 2 Power supplies and power sources shall be listed for use with electric signs and outline lighting systems and shall comply with 725.121.

(B) Grounding. Metal parts of signs and outline lighting systems shall be grounded and bonded in accordance with 600.7.

(C) Secondary Wiring. Secondary wiring from Class 2 power sources shall comply with 600.12(C).

II. Field-Installed Skeleton Tubing and Wiring

600.30 Applicability. Part II of this article shall apply to all of the following:

(1) Field-installed skeleton tubing

(2) Field-installed skeleton tubing wiring

These requirements are in addition to the requirements of Part I.

600.31 Neon Secondary-Circuit Wiring, 1000 Volts or

Less, Nominal.

(A) Wiring Method. Conductors shall be installed using any wiring method included in Chapter 3 suitable for the conditions.

(B) Insulation and Size. Conductors shall be listed, insu- lated, and not smaller than 18 AWG.

(C) Number of Conductors in Raceway. The number of conductors in a raceway shall be in accordance with Table 1 of Chapter 9.

(D) Installation. Conductors shall be installed so they are not subject to physical damage.

(E) Protection of Leads. Bushings shall be used to protect

wires passing through an opening in metal.

600.32 Neon Secondary-Circuit Wiring, over 1000

Volts, Nominal.

(A) Wiring Methods.

(1) Installation. Conductors shall be installed in rigid metal conduit, intermediate metal conduit, PVC conduit, RTRC, liquidtight flexible nonmetallic conduit, flexible metal conduit, liquidtight flexible metal conduit, electrical metallic tubing, metal enclosures, on insulators in metal raceways, or other equipment listed for use with neon secondary circuits over 1000 volts.

(2) Number of Conductors. Conduit or tubing shall con- tain only one conductor.

(3) Size. Conduit or tubing shall be a minimum of metric designator 16 (trade size Vi).

(4) Spacing from Grounded Parts. Other than at the lo- cation of connection to a metal enclosure or sign body, nonmetallic conduit or flexible nonmetallic conduit shall be spaced no less than 38 mm (IV2 in.) from grounded or bonded parts when the conduit contains a conductor operating at 100 Hz