Elevator and escalator motors are considered as intermittent duty. This allows them to be protected by the overcurrent protection device supplying the power for the branch circuit, which is selected by the percentages in NEC Table 430-22(a) 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?

6.3.2.5 GROUNDING

All metal raceways and cables, Types MC, Ml, or AC, shall be bonded to the metal frame of the car. All elevator equipment including metal enclosures for electric devices on the car shall be grounded in accordance with NEC Article 250.

6.3.2.6 OVERSPEED PROTECTION

Overspeed protection for overhauling and under-hauling is required, as are motor-generator overspeed requirements that must comply with NEC Section 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 require scrutiny by designers, maintenance personnel, and inspectors.

6.3.3 EMERGENCY POWER

Emergency power requirements are governed by ANSI/ASME A17.1 Rule 211.2, which requires that the regenerative power of an overhauling elevator prevent the elevator from attaining the lesser of the governor tripping speed or 125% of rated speed. If the elevator power system cannot absorb this power, a load shall 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, if required, 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 K, of the NEC, Overspeed, for the installation requirements covering these requirements.

6.3.4 DESIGN

In addition to the NEC, elevatorand escalatorrequirements, there are numerous electrical requirements for the facilities designer in ANSI/ASME A17.1 and A17.3. ANSI/ASME A17.1 is a required reference for new elevator and escalator installations and can be used by the designer in checking submittal drawings from the manufacturer. ANSI/ASME A17.3 provides the safety requirements for existing elevators and escalators and shall be referenced when existing installations are to be modified or to determine which modifications shall be made to existing installations and equipment to maintain optimum safety. The following lists typical key electrical requirements from ANSI/ ASME A17.1 that the designer shall control over and above those from the NEC.

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 hoistway may be installed in the hoistway.

4. A minimum lighting level of 1081ux for the equipment rooms and spaces and 541ux on the floor of the pit is required. The basis for the specified illumination level should be in accordance with the Illuminating Engineering Society (IES) lighting handbook.

5. A stop switch (emergency stop) is required in each elevator pit at the access door to the pit. If the pit exceeds 6 ft, 7 in., a second switch is required adjacent to the ladder. The two switches will be connected in series. See ANSI/ASME A17.1, Section 210.

6. Car lighting shall 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 shall be provided in all equipment spaces and in the pit.

8. A phase-reversal protection shall 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.