ELEVATORS, DUMBWAITERS

70-653 Exception: Higher voltages shall be permitted for frequencies of 25- through 60-hertz alternating current or for direct current, provided the current in the system cannot, under any conditions, exceed 8 milliamperes for alternating current or 30 milliamperes for direct current. (b) 600 Volts. Driving machine motors, machine brakes, and motorgenerator sets. Exception: Higher voltages shall be permitted for driving motors of motor-generator sets. 620-3. Live Parts Enclosed. All live parts of electric apparatus in the hoistways, at the landings, or in or on the cars of elevators and dumbwaiters or in the wellways or the landings of escalators or moving walks, or in the runways and machinery spaces of wheelchair lifts and stairway chair lifts shall be enclosed to protect against accidental contact. B. Conductors 620-11. Insulation of Conductors. The insulation of conductors installed in connection with elevators, dumbwaiters, escalators, moving walks, wheelchair lifts, and stairway chair lifts shall comply with (a) through (d) below. (a) Hoistway Door Interlock Wiring. The conductors to the hoistway door interlocks from the hoistway riser shall be flame-retardant and suitable for a temperature of not less than 200°C (392°F). Conductors shall be Type SF or equivalent. (b) Traveling Cables. Traveling cables used as flexible connections between the elevator or dumbwaiter car and the raceway shall be of the types of elevator cable listed in Table 400-4 or other approved types. (c) Other Wiring. All conductors in raceways; in or on the cars of elevators and dumbwaiters; in the wellways of escalators and moving walks; in the runways and machinery spaces of wheelchair lifts and stairway chair lifts; and in the machine room of elevators, dumbwaiters, escalators, and moving walks shall have flame-retardant insulation. (d) Insulation. All conductors shall have an insulation voltage rating equal to at least the maximum nominal circuit voltage rating of any conductor within the enclosure, cable, or raceway. Conductors shall be Type MTW, TF, TFF, TFN, TFFN, THHN, THW, THWN, TW, XHHW, hoistway cable, or any other conductor with insulation designated as flame-retardant. Shielded conductors shall be permitted, provided such conductors are insulated for the maximum voltage found in the cable or raceway system. 620-12. Minimum Size of Conductors. The minimum size of conductors used for elevator, dumbwaiter, escalator, moving walk, wheelchair lift, and stairway chair lift wiring, other than conductors that form an integral part of control equipment, shall be as follows: 70-654 NATIONAL ELECTRICAL CODE (a) Traveling Cables. (1) For lighting circuits: No. 14. Exception: No. 20 or larger conductors shall be permitted in parallel, provided the ampacity is equivalent to at least that of No. 14 wire. (2) Operating control and signaling circuits: No. 20. (b) Other Wiring. All operating control and signaling circuits: No. 24. 620-13. Motor Circuit Conductors. Conductors supplying elevator, dumbwaiter, escalator, moving walk, wheelchair lift, and stairway chair lift motors shall have an ampacity in accordance with (a) and (b) below based on the nameplate current rating of the motors. With generator field control, the ampacity shall be based on the nameplate current rating of the driving motor of the motor-generator set that supplies power to the elevator motor. (FPN): The heating of conductors depends on root-mean-square current values, which, with generator field control, are reflected by the nameplate current rating of the motor-generator set driving motor rather than by the rating of the elevator motor, which represents actual but short-time and intermittent full-load current values. (a) Conductors Supplying Single Motor. Conductors supplying a single motor shall have an ampacity in conformance with Section 430-22 and Table 430-22(a), Exception. (b) Conductors Supplying Several Motors. Conductors supplying two or more motors shall have an ampacity of not less than 125 percent of the nameplate current rating of the highest rated motor in the group plus the sum of the nameplate current ratings of the remainder of the motors in the group. 620-14. Adjustable Speed Drive Systems. Conductors supplying elevators, dumbwaiters, escalators, moving walks, wheelchair lifts, or stairway chair lifts shall have an ampacity in accordance with the following: (a) Drive Power Transformer Integral with the Power Conversion Equipment. Conductor ampacity shall be based on the nameplate current rating of the power conversion equipment. (b) Drive Power Transformer Not Integral with the Power Conversion Equipment. Conductor ampacity shall be based on the nameplate current rating of the drive power transformer and all other connected loads, or the nameplate current rating of the power conversion equipment reflected to the primary side of the transformer, plus all other connected loads, whichever is the larger. (FPN): Diagram 620-14 is for information only. 620-15. Feeder Demand Factor. Feeder conductors of less ampacity than required by Sections 620-13 and 620-14 shall be permitted subject to the requirements of Section 430-26 and Table 620-15. ARTICLE 620 - ELEVATORS, DUMBWAITERS 70-655 To supply To supply 620-14(a) 620-14(b) Common feeder Feeder demand factor Sec. 620-15 Disconnecting means Part F Overcurrent protection Part G Short-circuit and Art. 430 ground-fault Part D protection Branch circuit conductors to Sec. 620-14 external transformer External transformer Art. 450 Branch circuit Sec. 620-14 conductors to controller Sec. 620-13 Controller cabinet Sec. 620-14 rating Motor conductors Sec. 620-13(a) Part G Motor Thermal protection Art. 430 Parts A and c M M (FPN): Diagram 620-14 70-656 NATIONAL ELECTRICAL CODE Table 620-15. Feeder Demand Factors for Elevators Number of Elevators on a Single Feeder DF 1 1.00 2 .95 3 .90 4 .85 5 .82 6 .79 7 .77 8 .75 9 .73 10 or more .72 (FPN): Demand Factors (DF) are based on 50 percent duty cycle (i.e., half time on and half time off). C. Wiring 620-21. Wiring Methods. Conductors located in hoistways, in escalator and moving walk wellways, in wheelchair lifts, stairway chair lift runways, and machinery spaces, in or on cars, and in machine and control rooms, not including the traveling cables connecting the car and hoistway wiring, shall be installed in rigid metal conduit, intermediate metal conduit, electrical metallic tubing, rigid nonmetallic conduit, or wireways, or shall be Type MC, MI, or AC cable. Exception No. 1: Flexible metal conduit or liquidtight flexible metal conduit shall be permitted in hoistways and in escalator and moving walk wellways between risers and limit switches, interlocks, operating buttons, and similar devices. Cables used in Class 2 power-limited circuits (30 volts RMS or less or 42 VDC or less) shall be permitted to be installed between risers and signal fixtures and operating devices and within escalators and moving walkways and wheelchair lifts, and stairway chair lift runways and machinery spaces provided the cables are supported and protected from physical abuse and are of a jacketed and flame-retardant type. (FPN): Signal fixtures include audible and visual equipment such as chimes, gongs, lights, and displays that convey information to the elevator user. Exception No. 2: Flexible metal conduit or liquidtight flexible metal conduit not exceeding 6 feet (1.83 m) in length shall be permitted on cars where so located as to be free from oil and if securely fastened in place. Exception No. 3: Hard-service cords and junior hard-service cords conforming to the requirements of Article 400 (Table 400-4) shall be permitted as flexible connections between the fixed wiring on the car and devices on the car doors or gates. Hard-service cords only shall be permitted as flexible connections for the top-of-car operating device or the car-top work light. Devices or fixtures shall be grounded by means of an equipment grounding conductor run with the circuit conductors. Cables with smaller conductors and other types and thicknesses of insulation and jackets shall be permitted as flexible connections between the fixed wiring on the car and devices on the car doors or gates, if listed for this use. ARTICLE 620 - ELEVATORS, DUMBWAITERS 70-657 Exception No. 4: Flexible metal conduit or liquidtight flexible metal conduit, not exceeding 6 feet (1.83 m) in length, shall be permitted between control panels and machine motors, machine brakes, motor-generator sets, disconnecting means, and pumping unit motors and valves. Conductors shall also be permitted to be grouped together and taped or corded without being installed in a raceway. Such cable groups shall be supported at intervals not over 3 feet (914 mm) and so located as to be free from physical damage. Exception No. 5: Flexible metal conduit or liquidtight flexible metal conduit, of ³/₈-inch nominal trade size, shall be permitted in lengths not in excess of 6 feet (1.83 m). Exception No. 6: Flexible metal conduit, conforming to Article 350, or liquidtight flexible metal conduit, or hard-service cords conforming to the requirements of Article 400 (Table 400-4) shall be permitted as flexible connections on escalators, moving walk or elevator control panels and disconnecting means where the entire control panel and disconnecting means are arranged for removal from machine spaces as permitted in