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Article 610

Cranes and Hoists

Part I. General

  1. Scope. This article covers the installation of electrical equipment and wiring used in connection with cranes, mono‐ rail hoists, hoists, and all runways.Informational Note: For further information, see ASME B30, Safety Standards for Cableways, Cranes, Derricks, Hoists, Hooks, Jacks, and Slings.
  2. Definition.Festoon Cable. Single- and multiple-conductor cable intended for use and installation in accordance with Article 610 where flexibility is required.•
  3. Special Requirements for Particular Locations.
  1. Hazardous (Classified) Locations. All equipment that operates in a hazardous (classified) location shall conform to Article 500.
    1. Class I Locations. Equipment used in locations that are hazardous because of the presence of flammable gases or vapors shall conform to Article 501.
    2. Class II Locations. Equipment used in locations that are hazardous because of combustible dust shall conform to Arti‐ cle 502.
    3. Class III Locations. Equipment used in locations that are hazardous because of the presence of easily ignitible fibers or flyings shall conform to Article 503.
  2. Combustible Materials. Where a crane, hoist, or monorail hoist operates over readily combustible material, the resistors shall be located as permitted in the following:
    1. A well ventilated cabinet composed of noncombustible material constructed so that it does not emit flames or molten metal
    2. A cage or cab constructed of noncombustible material that encloses the sides of the cage or cab from the floor to a point at least 150 mm (6 in.) above the top of the resistors
  3. Electrolytic Cell Lines. See 668.32.

Part II. Wiring

  1. Wiring Method. Conductors shall be enclosed in race‐ ways or be Type AC cable with insulated grounding conductor, Type MC cable, or Type MI cable unless otherwise permitted or required in 610.11(A) through (E).
    1. Contact Conductor. Contact conductors shall not be required to be enclosed in raceways.
    2. Exposed Conductors. Short lengths of exposed conduc‐ tors at resistors, collectors, and other equipment shall not be required to be enclosed in raceways.
    3. Flexible Connections to Motors and Similar Equipment. Where flexible connections are necessary, flexible stranded conductors shall be used. Conductors shall be in flexible metal conduit, liquidtight flexible metal conduit, liquidtight flexible nonmetallic conduit, multiconductor cable, or an approved nonmetallic flexible raceway.
    4. Pushbutton Station Multiconductor Cable. Where multi‐ conductor cable is used with a suspended pushbutton station, the station shall be supported in some satisfactory manner that protects the electrical conductors against strain.
    5. Flexibility to Moving Parts. Where flexibility is required for power or control to moving parts, listed festoon cable or a cord suitable for the purpose shall be permitted, provided the following apply:
    1. Suitable strain relief and protection from physical damage is provided.
    2. In Class I, Division 2 locations, the cord is approved for extra-hard usage.
  2. Raceway or Cable Terminal Fittings. Conductors leav‐ ing raceways or cables shall comply with either 610.12(A) or (B).
    1. Separately Bushed Hole. A box or terminal fitting that has a separately bushed hole for each conductor shall be used wherever a change is made from a raceway or cable to exposed wiring. A fitting used for this purpose shall not contain taps or splices and shall not be used at luminaire outlets.
    2. Bushing in Lieu of a Box. A bushing shall be permitted to be used in lieu of a box at the end of a rigid metal conduit, intermediate metal conduit, or electrical metallic tubing where the raceway terminates at unenclosed controls or similar equip‐ ment, including contact conductors, collectors, resistors, brakes, power-circuit limit switches, and dc split-frame motors.
  3. Types of Conductors. Conductors shall comply with Table 310.104(A) unless otherwise permitted in 610.13(A) through (D).
    1. Exposed to External Heat or Connected to Resistors. A conductor(s) exposed to external heat or connected to resis‐ tors shall have a flame-resistant outer covering or be covered with flame-resistant tape individually or as a group.
    2. Contact Conductors. Contact conductors along runways, crane bridges, and monorails shall be permitted to be bare and shall be copper, aluminum, steel, or other alloys or combina‐ tions thereof in the form of hard-drawn wire, tees, angles, tee rails, or other stiff shapes.
    3. Flexibility. Where flexibility is required, listed flexible cord or cable, or listed festoon cable, shall be permitted to be used and, where necessary, cable reels or take-up devices shall be used.
    4. Class 1, Class 2, and Class 3 Circuits. Conductors for Class 1, Class 2, and Class 3 remote-control, signaling, and
    power-limited circuits, installed in accordance with Article 725, shall be permitted.
  4. Rating and Size of Conductors.
    1. Ampacity. The allowable ampacities of conductors shall be as shown in Table 610.14(A).Informational Note: For the ampacities of conductors between controllers and resistors, see 430.23.Table 610.14(A) Ampacities of Insulated Copper Conductors Used with Short-Time Rated Crane and Hoist Motors. Based on Ambient Temperature of 30°C (86°F).

      Maximum Operating Temperature
      Up to Four Simultaneously Energized Conductors in Raceway or Cable1Up to Three ac2 or Four dc1 Simultaneously Energized Conductors in Racewayor Cable
      Maximum Operating Temperature75°C (167°F)90°C (194°F)125°C (257°F)
      Size (AWG or kcmil)
      Types MTW, RHW, THW, THWN, XHHW, USE, ZWTypes TA, TBS, SA, SIS, PFA, FEP, FEPB, RHH, THHN, XHHW, Z, ZW
      Types FEP, FEPB, PFA, PFAH, SA, TFE, Z, ZW
      Size (AWG or kcmil)60 Min30 Min60 Min30 Min60 Min30 Min161012————1614252631323840141230333640455012104043495260651085560636973808676868394101119658595951061151345410011711113013315743120141131153153183321371601481731782142114317515819221025311/01902332112592533041/02/02222672452943033692/03/02803413053723704523/04/03003693193994515554/025036442040046151063525030045558249763658773730035048664654271666383735040053868859376074294140045060076566083681810424505006608477269148961143500
      AMPACITY CORRECTION FACTORSAmbient Temperature (°C)
      For ambient temperatures other than 30°C (86°F), multiply the ampacities shown above by the appropriate factor shown below.Ambient Temperature (°F)21–251.051.051.041.041.021.0270–7726–301.001.001.001.001.001.0079–8631–350.940.940.960.960.970.9788–9536–400.880.880.910.910.950.9597–10441–450.820.820.870.870.920.92106–11346–500.750.750.820.820.890.89115–12251–550.670.670.760.760.860.86124–131(continues)
      AMPACITY CORRECTION FACTORSAmbient Temperature (°C)
      For ambient temperatures other than 30°C (86°F), multiply the ampacities shown above by the appropriate factor shown below.Ambient Temperature (°F)56–600.580.580.710.710.830.83133–14061–700.330.330.580.580.760.76142–15871–80——0.410.410.690.69160–17681–90————0.610.61177–19491–100————0.510.51195–212101–120————0.400.40213–248Note: Other insulations shown in Table 310.104(A) and approved for the temperature and location shall be permitted to be substituted for those shown in Table 610.14(A). The allowable ampacities of conductors used with 15-minute motors shall be the 30-minute ratings increased by 12 percent.1 For 5 to 8 simultaneously energized power conductors in raceway or cable, the ampacity of each power conductor shall be reduced to a value of 80 percent of that shown in this table.2 For 4 to 6 simultaneously energized 125°C (257°F) ac power conductors in raceway or cable, the ampacity of each power conductor shall be reduced to a value of 80 percent of that shown in this table.
    2. Secondary Resistor Conductors. Where the secondary resistor is separate from the controller, the minimum size of the conductors between controller and resistor shall be calcula‐ ted by multiplying the motor secondary current by the appro‐ priate factor from Table 610.14(B) and selecting a wire from Table 610.14(A).
    3. Minimum Size. Conductors external to motors and controls shall be not smaller than 16 AWG unless otherwise permitted in (1) or (2):
      1. 18 AWG wire in multiconductor cord shall be permitted for control circuits not exceeding 7 amperes.
      2. Wires not smaller than 20 AWG shall be permitted for electronic circuits.
    4. Contact Conductors. Contact wires shall have an ampacity not less than that required by Table 610.14(A) for 75°C (167°F) wire, and in no case shall they be smaller than as shown in Table 610.14(D).
      Table 610.14(B) Secondary Conductor Rating Factors
      image
      On

      OffPercent of Full-Load Secondary Current5
      753510
      704515
      755515
      456515
      307515
      1585
      Continuous Duty
      110Time in Seconds Ampacity of Wire inimage
    5. Calculation of Motor Load.
      1. Single Motor. For one motor, 100 percent of motor name‐ plate full-load ampere rating shall be used.
      2. Multiple Motors on Single Crane or Hoist. For multiple motors on a single crane or hoist, the minimum ampacity of the power supply conductors shall be the nameplate full-load ampere rating of the largest motor or group of motors for any single crane motion, plus 50 percent of the nameplate full-load ampere rating of the next largest motor or group of motors, using that column of Table 610.14(A) that applies to the longest time-rated motor.
      3. Multiple Cranes or Hoists on a Common Conductor System. For multiple cranes, hoists, or both, supplied by a common conductor system, calculate the motor minimum ampacity shall be calculated for each crane as defined in 610.14(E), added them together, and the sum multiplied by the appropriate demand factor from Table 610.14(E).
    6. Other Loads. Additional loads, such as heating, lighting, and air conditioning, shall be provided for by application of the appropriate sections of this Code.
    7. Nameplate. Each crane, monorail, or hoist shall be provi‐ ded with a visible nameplate marked with the manufacturer’s name, rating in volts, frequency, number of phases, and circuit amperes as calculated in 610.14(E) and (F).
  5. Common Return. Where a crane or hoist is operated by more than one motor, a common-return conductor of proper ampacity shall be permitted.

Table 610.14(E) Demand Factors

Table 610.14(D) Minimum Contact Conductor Size Based on                                                                                                                                

Distance Between Supports

image

Number of Cranes or Hoists

Demand Factor

Minimum Size of Wire (AWG)

Maximum Distance Between End Strain Insulators or Clamp-Type Intermediate Supports

image

2 0.95

3 0.91

image

4 0.87

6 9.0 m (30 ft) or less

4 18 m (60 ft) or less

2 Over 18 m (60 ft)

5 0.84

6 0.81

7 0.78

Part III. Contact Conductors

  1. Installation of Contact Conductors. Contact conduc‐ tors shall comply with 610.21(A) through (H).
    1. Locating or Guarding Contact Conductors. Runway contact conductors shall be guarded, and bridge contact conductors shall be located or guarded in such a manner that persons cannot inadvertently touch energized current-carrying parts.
    2. Contact Wires. Wires that are used as contact conductors shall be secured at the ends by means of approved strain insula‐ tors and shall be mounted on approved insulators so that the extreme limit of displacement of the wire does not bring the latter within less than 38 mm (11∕2 in.) from the surface wired over.
    3. Supports Along Runways. Main contact conductors carried along runways shall be supported on insulating supports placed at intervals not exceeding 6.0 m (20 ft) unless otherwise permitted in 610.21(F).Such conductors shall be separated at not less than 150 mm (6 in.), other than for monorail hoists where a spacing of not less than 75 mm (3 in.) shall be permitted. Where necessary, intervals between insulating supports shall be permitted to be increased up to 12 m (40 ft), the separation between conduc‐ tors being increased proportionately.
    4. Supports on Bridges. Bridge wire contact conductors shall be kept at least 65 mm (21∕2 in.) apart, and, where the span exceeds 25 m (80 ft), insulating saddles shall be placed at inter‐ vals not exceeding 15 m (50 ft).
    5. Supports for Rigid Conductors. Conductors along runways and crane bridges, that are of the rigid type specified in 610.13(B) and not contained within an approved enclosed assembly, shall be carried on insulating supports spaced at intervals of not more than 80 times the vertical dimension of the conductor, but in no case greater than 4.5 m (15 ft), and spaced apart sufficiently to give a clear electrical separation of conductors or adjacent collectors of not less than 25 mm (1 in.).
    6. Track as Circuit Conductor. Monorail, tram rail, or crane runway tracks shall be permitted as a conductor of current for one phase of a 3-phase, ac system furnishing power to the carrier, crane, or trolley, provided all of the following condi‐ tions are met:
      1. The conductors supplying the other two phases of the power supply are insulated.
      2. The power for all phases is obtained from an insulating transformer.
      3. The voltage does not exceed 300 volts.
      4. The rail serving as a conductor shall be bonded to the equipment grounding conductor at the transformer and also shall be permitted to be grounded by the fittings used for the suspension or attachment of the rail to a building or structure.
    7. Electrical Continuity of Contact Conductors. All sections of contact conductors shall be mechanically joined to provide a continuous electrical connection.
    8. Not to Supply Other Equipment. Contact conductors shall not be used as feeders for any equipment other than the crane(s) or hoist(s) that they are primarily designed to serve.
  2. Collectors. Collectors shall be designed so as to reduce to a minimum sparking between them and the contact conductor; and, where operated in rooms used for the storage of easily ignitible combustible fibers and materials, they shall comply with 503.155.

Part IV. Disconnecting Means

  1. Runway Conductor Disconnecting Means. A discon‐ necting means that has a continuous ampere rating not less than that calculated in 610.14(E) and (F) shall be provided between the runway contact conductors and the power supply. The disconnecting means shall comply with 430.109. This disconnecting means shall be as follows:
    1. Readily accessible and operable from the ground or floor level
    2. Lockable open in accordance with 110.25
    3. Open all ungrounded conductors simultaneously
    4. Placed within view of the runway contact conductors
    Exception: The runway conductor disconnecting means for electrolytic cell lines shall be permitted to be placed out of view of the runway contact conductors where either of the following conditions are met:
    1. Where a location in view of the contact conductors is impractica‐ ble or introduces additional or increased hazards to persons or property
    2. In industrial installations, with written safety procedures, where conditions of maintenance and supervision ensure that only qualified persons service the equipment
  2. Disconnecting Means for Cranes and Monorail Hoists. A disconnecting means in compliance with 430.109 shall be provided in the leads from the runway contact conductors or other power supply on all cranes and monorail hoists. The disconnecting means shall be lockable open in accordance with 110.25.Where a monorail hoist or hand-propelled crane bridge installation meets all of the following, the disconnecting means shall be permitted to be omitted:
    1. The unit is controlled from the ground or floor level.
    2. The unit is within view of the power supply disconnecting means.
    3. No fixed work platform has been provided for servicing the unit.
    Means shall be provided at the operating station to open the power circuit to all motors of the crane or monorail hoist.
  3. Rating of Disconnecting Means. The continuous ampere rating of the switch or circuit breaker required by

610.32 shall not be less than 50 percent of the combined short- time ampere rating of the motors or less than 75 percent of the sum of the short-time ampere rating of the motors required for any single motion.

Part V. Overcurrent Protection

  1. Feeders, Runway Conductors.
    1. Single Feeder. The runway supply conductors and main contact conductors of a crane or monorail shall be protected by an overcurrent device(s) that shall not be greater than the largest rating or setting of any branch-circuit protective device
      plus the sum of the nameplate ratings of all the other loads with application of the demand factors from Table 610.14(E).
    2. More Than One Feeder Circuit. Where more than one feeder circuit is installed to supply runway conductors, each feeder circuit shall be sized and protected in compliance with 610.41(A).
  2. Branch-Circuit Short-Circuit and Ground-Fault Protec‐ tion. Branch circuits shall be protected in accordance with 610.42(A). Branch-circuit taps, where made, shall comply with 610.42(B).
    1. Fuse or Circuit Breaker Rating. Crane, hoist, and mono‐ rail hoist motor branch circuits shall be protected by fuses or inverse-time circuit breakers that have a rating in accordance with Table 430.52. Where two or more motors operate a single motion, the sum of their nameplate current ratings shall be considered as that of a single motor.
    2. Taps.
      1. Multiple Motors. Where two or more motors are connec‐ ted to the same branch circuit, each tap conductor to an indi‐ vidual motor shall have an ampacity not less than one-third that of the branch circuit. Each motor shall be protected from over‐ load according to 610.43.
      2. Control Circuits. Where taps to control circuits originate on the load side of a branch-circuit protective device, each tap and piece of equipment shall be protected in accordance with 430.72.
    •
  3. Overload Protection.
  1. Motor and Branch-Circuit Overload Protection. Each motor, motor controller, and branch-circuit conductor shall be protected from overload by one of the following means:
    1. A single motor shall be considered as protected where the branch-circuit overcurrent device meets the rating requirements of 610.42.
    2. Overload relay elements in each ungrounded circuit conductor, with all relay elements protected from short circuit by the branch-circuit protection.
    3. Thermal sensing devices, sensitive to motor temperature or to temperature and current, that are thermally in contact with the motor winding(s). Hoist functions shall be considered to be protected if the sensing device limits the hoist to lowering only during an overload condition. Traverse functions shall be considered to be protected if the sensing device limits the travel in both directions for the affected function during an overload condition of either motor.
  2. Manually Controlled Motor. If the motor is manually controlled, with spring return controls, the overload protective device shall not be required to protect the motor against stalled rotor conditions.
  3. Multimotor. Where two or more motors drive a single trolley, truck, or bridge and are controlled as a unit and protec‐ ted by a single set of overload devices with a rating equal to the sum of their rated full-load currents, a hoist or trolley shall be considered to be protected if the sensing device is connected in the hoist’s upper limit switch circuit so as to prevent further hoisting during an overtemperature condition of either motor.
  4. Hoists and Monorail Hoists. Hoists and monorail hoists and their trolleys that are not used as part of an overhead trav‐ eling crane shall not require individual motor overload protec‐ tion, provided the largest motor does not exceed 71∕2 hp and all motors are under manual control of the operator.

Part VI. Control

610.51 Separate Controllers. Each motor shall be provided with an individual controller unless otherwise permitted in 610.51(A) or (B).

  1. Motions with More Than One Motor. Where two or more motors drive a single hoist, carriage, truck, or bridge, they shall be permitted to be controlled by a single controller.
  2. Multiple Motion Controller. One controller shall be permitted to be switched between motors, under the following conditions:
  1. The controller has a horsepower rating that is not lower than the horsepower rating of the largest motor.
  2. Only one motor is operated at one time.

610.53 Overcurrent Protection. Conductors of control circuits shall be protected against overcurrent. Control circuits shall be considered as protected by overcurrent devices that are rated or set at not more than 300 percent of the ampacity of the control conductors, unless otherwise permitted in 610.53(A) or (B).

  1. Taps to Control Transformers. Taps to control transform‐ ers shall be considered as protected where the secondary circuit is protected by a device rated or set at not more than 200 percent of the rated secondary current of the transformer and not more than 200 percent of the ampacity of the control circuit conductors.
  2. Continuity of Power. Where the opening of the control circuit would create a hazard, as for example, the control circuit of a hot metal crane, the control circuit conductors shall be considered as being properly protected by the branch- circuit overcurrent devices.

•

610.57 Clearance. The dimension of the working space in the

direction of access to live parts that are likely to require exami‐ nation, adjustment, servicing, or maintenance while energized shall be a minimum of 750 mm (21∕2 ft). Where controls are enclosed in cabinets, the door(s) shall either open at least 90 degrees or be removable.

Part VII. Grounding

610.61 Grounding. All exposed non–current-carrying metal parts of cranes, monorail hoists, hoists, and accessories, includ‐ ing pendant controls, shall be bonded either by mechanical connections or bonding jumpers, where applicable, so that the entire crane or hoist is a ground-fault current path as required or permitted by Article 250, Parts V and VII.

Moving parts, other than removable accessories, or attach‐ ments that have metal-to-metal bearing surfaces, shall be considered to be electrically bonded to each other through bearing surfaces for grounding purposes. The trolley frame and bridge frame shall not be considered as electrically groun‐ ded through the bridge and trolley wheels and its respective tracks. A separate bonding conductor shall be provided.

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