Transformer secondary conductors other than 2-wire shall not be considered to be protected by the primary overcurrent protection.
(E) Input Side of Electronic Power Source. Class 1 cir cuit conductors supplied by the output of a single- phase, listed electronic power source, other than a transformer, having only a 2-wire (single-voltage) output for connection to Class 1 circuits shall be permitted to be protected by overcurrent protection provided on the input side of the electronic power source, provided this protection does not exceed the value determined by multiplying the Class 1 circuit conductor ampacity by the output-to-input voltage ratio. Electronic power source outputs, other than 2- wire (single voltage), shall not be considered to be protected by the primary overcurrent protection.
725.46 Class 1 Circuit Wiring Methods. Class 1 circuits shall be installed in accordance with Part I of Article 300 and with the wiring methods from the appropriate articles in Chapter 3.
Exception No. 1: The provisions of 725.48 through
725.51 shall be permitted to apply in installations of
Class 1 circuits.
Exception No. 2: Methods permitted or required by other articles of this Code shall apply to installations of Class 1 circuits.
725.48 Conductors of Different Circuits in the Same Cable, Cable Tray, Enclosure, or Raceway. Class 1 cir- cuits shall be permitted to be installed with other circuits as specified in 725.48(A) and (B).
(A) Two or More Class 1 Circuits. Class 1 circuits shall be
permitted to occupy the same cable, cable tray, enclosure, or raceway without regard to whether the individual circuits are alternating current or direct current, provided all conductors are insulated for the maximum voltage of any conductor in the cable, cable tray, enclosure, or raceway.
(B) Class 1 Circuits with Power-Supply Circuits. Class 1 circuits shall be permitted to be installed with power- supply conductors as specified in 725.48(B)(1) through (B)(4).
(1) In a Cable, Enclosure, or Raceway. Class 1 circuits
and power-supply circuits shall be permitted to occupy
the same cable, enclosure, or raceway only where the
equipment powered is functionally associated.
(2) In Factory- or Field-Assembled Control Centers. Class
1 circuits and power-supply circuits shall be permitted to
be installed in factory- or field-assembled control
centers.
(3) In a Manhole. Class 1 circuits and power-supply cir- cuits shall be permitted to be installed as underground conductors in a manhole in accordance with one of the following:
(1) The power-supply or Class 1 circuit conductors are in a metal-enclosed cable or Type UF cable.
(2) The conductors are permanently separated from the power-supply conductors by a continuous firmly fixed nonconductor, such as flexible tubing, in addition to the insulation on the wire.
(3) The conductors are permanently and effectively separated from the power supply conductors and securely fastened to racks, insulators, or other approved supports.