Elevator Troubleshooting & Repair. David Herres

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СКАЧАТЬ installations with a few exceptions such as installations under the direct control of utilities, and underground in mines. (It does, however, govern non-mine installations such as lighting and signal wiring in underground traffic tunnels.) NEC has no legal standing on its own, but is offered up for adoption and enforcement by states, municipalities, and jurisdictions inside and outside the United States.

      NEC Article 620, part of Chapter 6, covers elevators, dumbwaiters, escalators, moving walks, platform lifts, and stairway lifts. Each of these performs a different set of functions with different requirements. The section on elevators contains specific electrical requirements, which must be observed in new installations. It is not the intent of NEC that with each Code revision all existing installations are to be immediately upgraded to comply. Nevertheless, older installations should be critically evaluated to see where upgrades are feasible and/or warranted. Besides Article 620, new elevator installations must comply with the entire electrical code except where specifically exempted. Two very important articles are 250, Grounding, and 430, Motors, Motor Circuits and Controllers.

      I will return to the very important subject of codes in this Introduction and in fact throughout the book, but first a few paragraphs about licensing.

      If you are serious about engaging in elevator work, you should acquire the appropriate license(s)—electrician’s license and elevator mechanic’s license. This is not going to happen all at once. Most states require verified work experience and/ or completion of classroom or online training, including passage of an exam, plus the state exam. There is no single nationwide electrician’s or elevator technician’s license. For the most part in the United States these permits are issued and regulated by the individual states, or in a few instances jurisdiction is ceded over to separate counties or municipalities. Most states maintain electrical and elevator agencies, which inspect installations and issue technicians’ and other permits. Requirements vary widely from state to state. The best approach as a start is to check your state’s website for requirements and procedures for obtaining the appropriate licenses.

      My home state, New Hampshire, requires electricians’ licensing for those who are performing electrical installations for heat, light, and power purposes regardless of the voltage. It is not the voltage of the circuit that determines the requirements of licensure, it is the type of circuit. Accordingly, an individual can work on a central fire alarm system without having an electrician’s license, because the electrical system is for signaling, not heat, light, or power. How does this apply to elevator work? Most inspectors, technically known as the authorities having jurisdiction, will recognize that elevators, as we shall see in the chapters that follow, are composed of both signaling and power electrical circuits. Therefore, the electrician’s license would not be required to work on the signaling and control circuitry, in the car, on individual floors where the call buttons are located, in the machine room, or in the motion controller. However, the electrician’s license would be required to work on the power path from the entrance panel, through the main disconnect, to the variable frequency drive (VFD) and motor. The electrician’s license would also be required to work on lighting and branch-circuit receptacles in the pit and machine room. (In most cases a licensed electrician would in fact work on the signal wiring, but for this the license would not absolutely be required.) The bottom line is that if you are serious about doing elevator work, you should obtain the electrician’s license.

      The New Hampshire Board licenses three categories: master, journeyman, and high/medium voltage electricians. In addition, it registers apprentice electricians and high/medium voltage trainees. All electrical work for which an electrician’s license is required must be overseen by a licensed master electrician. This individual need not be at the jobsite at all times, but is responsible for seeing that the work complies with the National Electrical Code. Journeyman electricians may perform the on-site electrical work, but they may not work on their own as independent contractors. Apprentice electricians may also perform electrical work, but they must be supervised by journeyman electricians, who must be on-site whenever apprentices are working. A one-on-one ratio must be maintained. If there are two apprentice electricians performing electrical work, there must be two journeyman or master electricians at the site.

      To receive a master electrician’s license, the individual must have 8000 hours practical experience as an apprentice to a licensed electrician and at least one of the following:

      ■ 575 hours of electrical schooling in blocks of 144 hours per year or have an associate or higher degree in an electrical curriculum

      ■ Have ten years experience as a journeyman or master electrician as required in another jurisdiction; or Have taken the journeyman or master exam in New Hampshire previously

      ■ Acquired credit or school time, not to exceed 2000 hours, towards the practical experience requirement or completion of prescribed courses in electrical installations at an approved school

      ■ Pass the journeyman examination and obtain 2000 hours of experience as a journeyman in performing electrical installations prior to being examined

      The master electrician exam consists of 50 NEC questions, 50 questions on practical installations, and 25 questions on applicable state laws and the Board’s administrative rules. The license fee is $270 for three years. To receive a journeyman electrician’s license, the requirements are substantially the same, but the exam is less difficult. The fee is $150 for three years.

      The apprentice is not required to take an examination or have work experience prior to application, but must possess a high school diploma or equivalent. The fee for the apprentice card is $30, and it is valid for one year. During that period the apprentice is expected to complete 150 hours of vocational training and to study for the journeyman’s license. New Hampshire also issues an elevator mechanic’s license. Considerable practical experience working with a licensed individual is required to obtain this license, so it would be a long-range goal.

      The American Society of Mechanical Engineers (ASME), through its Board on Safety Codes and Standards (BSCS), develops and maintains a comprehensive portfolio of codes and standards that governs elevators and escalators. A complete listing can be seen at ASME.org.

      ASME A17, Safety Code for Existing Elevators and Escalators, is an essential reference for elevator maintenance workers and repair technicians. It can be ordered online at ASME.org. After a few paragraphs on Purpose and Exceptions, ASME A17 lists pertinent definitions. Here, by way of overview, are some highlights, with references to escalators, moving walks, and material lifts eliminated because they are outside the scope of this textbook.

      ■ Car annunciator: An electrical device in the car that indicates visually the landings at which an elevator landing signal registering device has been actuated.

      ■ Auxiliary power lowering device: An alternatively powered auxiliary control system that will, upon failure of the main power supply, allow a hydraulic elevator to descend to a lower landing.

      ■ Emergency brake: A mechanical device independent of the braking system used to retard or stop an elevator should the car overspeed or move in an unintended manner. Such devices include, but are not limited to, those that apply braking force on car rails, counterweight rails, suspension or compensation ropes, drive sheaves, and brake drums.

      ■ Buffer: A device designed to stop a descending car or counterweight beyond its normal limit of travel by storing or by absorbing and dissipating the kinetic energy of the car or counterweight.

      ■ Bumper: A device, other than an oil or spring buffer, designed to stop a descending car or counterweight beyond its normal limit of travel by absorbing the impact.

      ■ Car-direction indicator: A visual СКАЧАТЬ