Results 1 to 4 of 4

Thread: Hoist Disconnect Switch

  1. #1
    Join Date
    Nov 2005
    Posts
    2

    Hoist Disconnect Switch

    With reference to NEC section 610:31/32:

    I have a situation where an electric hoist & trolley is being installed for maintenance of equipment in a Cl. II, Div. 1, Gr.F area. The hoist is powered from a 480 VAC feeder circuit breaker in a MCC located out of sight, in an electrical room several hundred feet from the hoist & trolley. The hoist is mounted on an I-beam from the ceiling (15' high) and includes a flexible cable festoon to allow movement of the hoist by the trolley along the beam. The hoist is fed by a single 480 VAC feed and internally the hoist has been supplied with motor starters for each of the hoist and trolley motors, which are controlled by a pushbutton pendant station hanging down from the hoist.

    Is a local disconnect switch required for the hoist and trolley, even though the plant may have a lockout/taggout procedure and can shut-off power via the CB at the MCC?

    If a local disconnect switch is required, would it be required to be located at the ground level, within sight of the hoist, where it would be readily accessible? Or should it be part of the hoist & trolley electrical enclosure itself or installed just prior to the festoon cable, both at ceiling height?

  2. #2
    Join Date
    Dec 2004
    Location
    North Carolina
    Posts
    4,446

    Re: Hoist Disconnect Switch

    610.32 Disconnecting Means for Cranes and Monorail Hoists.
    A motor-circuit switch, molded-case switch, or circuit breaker 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 capable of being locked in the open position.
    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.
    Where the disconnecting means is not readily accessible from the crane or monorail hoist operating station, means shall be provided at the operating station to open the power circuit to all motors of the crane or monorail hoist.

    502.115 Switches, Circuit Breakers, Motor Controllers, and Fuses.
    (A) Class II, Division 1. In Class II, Division 1 locations, switches, circuit breakers, motor controllers, and fuses shall comply with 502.115(A)(1) through (A)(3).
    (1) Type Required. Switches, circuit breakers, motor controllers, and fuses, including pushbuttons, relays, and similar devices that are intended to interrupt current during normal operation or that are installed where combustible dusts of an electrically conductive nature may be present, shall be provided with identified dust-ignitionproof enclosures.
    (2) Isolating Switches. Disconnecting and isolating switches containing no fuses and not intended to interrupt current and not installed where dusts may be of an electrically conductive nature shall be provided with tight metal enclosures that shall be designed to minimize the entrance of dust and that shall (1) be equipped with telescoping or close-fitting covers or with other effective means to prevent the escape of sparks or burning material and (2) have no openings (such as holes for attachment screws) through which, after installation, sparks or burning material might escape or through which exterior accumulations of dust or adjacent combustible material might be ignited.
    (3) Metal Dusts. In locations where dust from magnesium, aluminum, aluminum bronze powders, or other metals of similarly hazardous characteristics may be present, fuses, switches, motor controllers, and circuit breakers shall have enclosures identified for such locations.
    Mike Whitt
    God answers Knee-Mail.

  3. #3
    Join Date
    Nov 2005
    Posts
    2

    Re: Hoist Disconnect Switch

    Thanks jwelectric for writing out the sections of the NEC I was pondering, however, it did not help me resolve the questions I posed.

    I guess I do not understand what is meant by the "runway contact conductor" when they indicate that a disconnect shall be provided in the leads from the runway contact conductors or other power supply on all cranes and monorail hoists. Does the circuit breaker at the MCC that feeds power to the hoist enclosure meet this and does this maintenance hoist fall under the definition of a "monorail" hoist?

  4. #4
    Join Date
    Dec 2004
    Location
    North Carolina
    Posts
    4,446

    Re: Hoist Disconnect Switch

    In both 610.31 and 32 it states that a disconnect must be with in view of the equipment. 610.32 gives relief that if a working platform is not located where the motors are located then this disconnect can be at floor level.

    If the breaker that you speak of in the Motor Control Center is not in view of the crane then you will need to install one that is.

    This disconnect will be required to adhere to the class of its location.
    Mike Whitt
    God answers Knee-Mail.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •