Class 2 srl

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## SPECIAL SYSTEMS - (iv) Disconnecting means. A disconnecting means that simultaneously opens all ungrounded conductors shall be installed at each transformer or motor location. - (v) Grounding and bonding. All non-energized metal parts of electric equipment and metal raceways and cable sheaths shall be grounded and bonded to all metal pipes and rails at the portal and at intervals not exceeding 1000 feet (305 m) throughout the tunnel. - (b) Class 1, Class 2, and Class 3 remote control, signaling, and power-limited circuits. - (1) Classification. Class 1, Class 2, or Class 3 remote control, signaling, or powerlimited circuits are characterized by their usage and electrical power limitation which differentiates them from light and power circuits. These circuits are classified in accordance with their respective voltage and power limitations as summarized in paragraphs (b)(1)(i) through (b)(1)(iii) of this section. ## (i) Class 1 circuits. - (A) A Class 1 power-limited circuit is supplied from a source having a rated output of not more than 30 volts and 1000 volt-amperes. - (B) A Class 1 remote control circuit or a Class 1 signaling circuit has a voltage which does not exceed 600 volts; however, the power output of the source need not be limited. ## (ii) Class 2 and Class 3 circuits. - (A) Power for Class 2 and Class 3 circuits is limited either inherently (in which no overcurrent protection is required) or by a combination of a power source and overcurrent protection. - (B) The maximum circuit voltage is 150 volts AC or DC for a Class 2 inherently limited power source, and 100 volts AC or DC for a Class 3 inherently limited power source. - (C) The maximum circuit voltage is 30 volts AC and 60 volts DC for a Class 2 power source limited by overcurrent protection, and 150 volts AC or DC for a Class 3 power source limited by overcurrent protection. - (iii) Application. The maximum circuit voltages in paragraphs (b)(1)(i) and (b)(1)(ii) of this section apply to s…

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\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ - (iii) The power source for a Class 2 or Class 3 circuit must be listed equipment marked as a Class 2 or Class 3 power source, except as follows: - (A) Thermocouples do not require listing as a Class 2 power source; and - (B) A dry cell battery is considered an inherently limited Class 2 power source, provided the voltage is 30 volts or less and the capacity is less than or equal to that available from series-connected No. 6 carbon zinc cells. - (b) Marking . You must durably mark a Class 2 or Class 3 power supply unit where plainly visible to indicate the class of supply and its electrical rating. - (c) Separation from conductors of other circuits . Cables and conductors of Class 2 and Class 3 circuits may not be placed in any cable, cable tray, compartment, enclosure, manhole, outlet box, device box, raceway, or similar fitting with conductors of electric light, power, Class 1, nonpower-limited fire alarm circuits, and medium power network-powered broadband communications cables unless a barrier or other equivalent form of protection against contact is employed. ## (4) Fire alarm systems . - (a) Classifications . You must classify fire alarm circuits either as nonpower limited or power limited. - (b) Power sources . The power sources for use with fire alarm circuits must be either power limited or nonpower limited as follows: - (i) The power source of nonpower-limited fire alarm (NPLFA) circuits must have an output voltage of not more than 600 volts, nominal; and - (ii) The power source for a power-limited fire alarm (PLFA) circuit must be listed equipment marked as a PLFA power source. ## (c) Separation from conductors of other circuits . - (i) Nonpower-limited fire alarm circuits and Class 1 circuits may occupy the same enclosure, cable, or race…