Fig. 7-3. Clearance distances between equipment and overhead lines.
7.3.2.2 Disconnecting Means
The disconnecting means requirements for elevators and escalators are both specific and extensive, requiring careful study of the codes and installation plans during design, acceptance testing, and routine inspections. Some of the basic requirements of NEC 620.51 are the following:
1. There shall7.26 be a single means of disconnecting all ungrounded conductors to the main power supply of each unit.
2. A single elevator or escalator, with multiple driving machines, shall7.26 have one disconnecting means to disconnect the motors and control valve operating magnets.
3. When there is more than one driving machine in a machine room, the disconnecting means shall7.27 be labeled.
4. The disconnect shall7.28 be a fused motor circuit switch or circuit breaker capable of being locked open.
5. The disconnect shall7.29 not be provided with a means of being operated from a remote location.
6. A circuit breaker disconnecting means shall7.29 not be opened automatically by a fire alarm system, except as allowed by NEC.
7. The within-sight rule applies to all elevator equipment disconnects. Specific locations are given for elevators with or without field control.
8. The disconnecting means shall7.30 be installed in a location that is readily accessible to only qualified persons.
When power from more than one source is used for single- or multiple-car installations, a separate disconnect shall (NEC 620.52) be provided for each source. These disconnects shall (NEC 620.52) be in sight of the equipment supplied, and warning signs shall (NEC 620.52) be placed on or adjacent to the disconnect and shall (NEC 620.52) read, Warning: Parts of the control panel are not de-energized by this switch.
Lighting circuits for each elevator shall (NEC 620.53) have a disconnect switch in the equipment room labeled for the car it serves and lockable in the open position.
7.3.2.3 Motors
Elevator and escalator motors are considered as intermittent duty. This allows them to be protected by the OCDP supplying the power for the branch circuit, which is selected by the percentages in NEC Table 430.22 times the full load current of the motors. For example: What is the load for a 15-minute rated 40-HP, 460-V, three-phase motor used as a freight elevator motor?
Step 1: Finding full load current — NEC Table 430.150 40 HP = 52 A
Step 2: Finding demand factors — NEC Table 430.22 (a) 15 minute rated = 85%
Step 3: Calculating load 52 A x 85% = 44.2A Answer: Load is 44.2 amps.
7.3.2.4 Grounding
All metal raceways and cables, types metal clad (MC), mineral insulated (Ml), or AC, shall7.31 be bonded to the metal frame of the car. All elevator equipment including metal enclosures for electric devices on the car shall7.32 be bonded in accordance with NEC Article 250.
7.3.2.5 Overspeed Protection
Overspeed protection for overhauling and underhauling is required, as are motor-generator overspeed requirements that shall comply with NEC 430.89, Speed Limitation. However, these requirements are a part of the more extensive requirements of ANSI/ASME A17.1 for electrical safety devices, which warrant scrutiny by designers, maintenance personnel, and inspectors.
7.3.3 Emergency Power
Emergency power requirements are governed by ANSI/ASME A17.1, Section 2.26.10 and 2.27.25, which require that the regenerative power of an overhauling elevator prevents the elevator from attaining the lesser of the governor tripping speed or 125% of the rated speed. If the elevator power system cannot absorb this power, a load should be provided on the load side of the elevator power disconnect switch. If an emergency power supply is designed to operate only one elevator at a time, the energy absorption means may be located on the line side of the disconnect. Other building loads that may be supplied by the emergency power source may not be considered as absorbing regenerated energy unless they use the emergency power source as normal power. Refer to Article 620, Part X, of the NEC, Overspeed, for the installation requirements covering these requirements.
7.3.4 Design
In addition to the NEC, elevator and escalator requirements, there are numerous electrical requirements for facility designers in ANSI/ASME A17.1 and A17.3. The designer in checking submittal drawings from the manufacturer can use A17.1. ANSI/ASME A17.3 provides the safety requirements for existing elevators and escalators and should be referenced when existing installations are to be modified or to determine which modifications should be made to existing installations and equipment to maintain optimum safety. Typical key electrical requirements from ANSI/ASME A17.1 that the designer should control, over and above those from the NEC, include:
1. Access to elevator equipment is to be controlled and limited to authorized persons.
2. Elevator equipment cannot share space with other building equipment except when the elevator equipment is separated from other equipment, enclosed by a rigid wire fence, and provided with a lock that is strictly for that enclosure.
3. Only electrical wiring, including raceways and cables, used directly in connection with the elevator, including wiring for: (a) signals; (b) communication with the car; (c) lighting, heating, air conditioning, and ventilating the car; (d) fire-detecting systems; (e) pit sump pumps; and, (f) heating and lighting the hoist way, may be installed in the hoist way.
4. A minimum lighting level of 200 lux (19 foot candles (fc)) for the equipment rooms and spaces and 541 lux on the floor of the pit is cited. The basis for the specified illumination level should be in accordance with the Illuminating Engineering Society lighting handbook.
5. A stop switch (emergency stop) is necessary in each elevator pit at the access door to the pit. If the pit exceeds 6 feet 7 inches, a second switch is necessary adjacent to the ladder. The two switches are connected in series.
6. Car lighting should consist of a minimum of two lamps to be supplied by a dedicated circuit with a lock-open disconnect in the equipment room.
7. A 115-V, 20-A receptacle shall7.33 be provided in all equipment spaces and in the pit.
8. A phase-reversal protection should be provided to ensure that the elevator motor cannot start if the phase rotation is in the wrong direction, or if there is a failure of any phase.
9. Capacitors and other devices whose failure could cause unsafe elevator operation are prohibited. Only devices specified by the NEC or the manufacturer may be installed.
7.3.5 Fire Protection
The electrical designer should coordinate with the manufacturer on the design of the fire protection systems that connect to the elevator control panel. The system is designed to return the car to a designated area (normally the first floor or lobby) in the event of smoke or fire in the equipment area or near the elevators. In that event, the car returns to a designated area where passengers can safely exit the facility. In addition to coordinating car control, the system provides for the shutdown of the electrical elevator equipment prior to operation of the sprinklers and the transmission of the alarm and provides a means for the firefighters to assume manual control of the elevator from the designated area. The specifications for these systems are detailed in ANSI/ASME A17.1.
7.3.6 Inspections and Records
Elevator inspections and recordkeeping are performed in accordance with the local AHJ. The ANSI/ASME A17.2 series of inspectors’ manuals provide a guide for performing tests and inspections as well as recommended inspection checklists. In addition to acceptance inspections and tests, the elevator code specifies one- and five-year inspections for electric elevators and one- and three-year inspections for hydraulic elevators.
7.3.6.1 Codes
Elevators should be in compliance with the issue of ANSI/ASME A17.1 in force the date they were installed. If the local authority has adopted ANSI/ASME A17.3, the code for existing installations, elevators should be in compliance with it, except they should not be downgraded to it. When ANSI/ASME A17.3 is in force, it becomes the minimum standard to which installations should adhere, and if existing installations are upgraded in accordance with ANSI/ASME A17.1, Chapter 8, they should also be in compliance with the more stringent requirements of A17.3.
7.3.6.2 Inspector Qualifications
Inspectors should meet the requirements of OSHA and ANSI/ASME QEI-1 and be recognized by the local enforcing authority. Repair and maintenance personnel should be qualified elevator mechanics.