ALLOWABLE MOTOR STARTING CURRENTS

The Company will permit limited size single and three phase motors to be connected to its lines without any reduced voltage starters, provided that the locked rotor currents do not exceed the following values:

A. EQUIPMENT WITH MOTORS RATED IN HORSEPOWER

B. ROOM & UNITARY AIR CONDITIONING OR HEAT PUMP EQUIPMENT, RATED IN BTU'S/HOUR

The limitations given in Tables A and B are based on a maximum of four (4) starts per hour, with long periods of continuous operation under maximum load conditions. (Exception - domestic laundry equipment with presently available operating cycles and electrical characteristics is considered acceptable.) Consult the Company where these conditions cannot be met, or where equipment rating and/or starting characteristics exceed the values listed in Tables A & B.

Where the equipment contains more than one (1) motor, and some motors are arranged for sequence (increment) starting, the information above applies to that combination of power consuming components simultaneously started, that produces a higher current than any other combination. The interval between successive steps shall not be less than one-half second.

Where the design of the equipment is such that unequal currents appear in the supply wires, (i.e. 115 volt auxiliary meters on 230 volt, single phase equipment or single phase auxiliary meters on three phase equipment), the information above applies to the supply wire carrying the largest current.

For polyphase motors and equipment rated at voltages other than 230 volts, the locked rotor currents specified in Tables A & B shall be multiplied by the inverse ratio of the voltages (Example: For a motor rated 460 volts, the ratio would be 230/460, and the allowable current would be 1/2 the value specified in the information above ).

Where three phase service is available or where it can be made available in accordance with the filed tariff regulations and applicable line extension policies, such service is recommended for installations consisting of three phase motors of more than 7-1/2 horsepower. This statement does not imply that any single motor rated at less than 7-1/2 horsepower must be supplied with single phase service since some compressors etc. are limited to around five (5) hp single phase. The intent is to establish a lower threshold beneath which the Company does not recommend utilizing three phase service. The determination to use single or three phase service for a motor load in the range of 7-1/2 horsepower must be made on the basis of voltage drop and flicker criteria. Where 120/240 or 120/208 volt service is supplied, the Company prefers that all larger motors (i.e. greater than three (3) horsepower) be connected for the higher phase voltage( i.e. 208V or 240V versus 120V). The Company may require reduced voltage starting devices on any motor not complying with the requirements specified in Tables A & B above.

PROTECTIVE EQUIPMENT

The Company recommends that undervoltage time delay tripping mechanisms be installed on all motors that are not equipped and /or cannot be operated safely with low voltage releases. These mechanisms provide protection from sustained undervoltage, and protect against instantaneous disconnection of equipment due to momentary voltage fluctuations or interruptions.

Protection against loss of voltage, voltage unbalance, undervoltage transient, sustained overvoltage, phase reversal, loss of sychronism, overcurrent, short circuit and single phasing is highly recommended for three phase equipment and is the responsibility of the Customer. Reverse phase relays must be provided on three phase motors for elevators, cranes, hoists, or any other equipment requiring constant direction of rotation, where reversal of power would result in damage to the equipment.

The Company recommends that all motors, particularly three phase, be equipment with thermal overload protective devices. These devices are used to protect against dangerous overheating of the motor due to overload and failure to start. Overcurrent protective devices which open the circuit on overload must have adequate interrupting capacity, and comply with the requirements of National Electrical Code Article 430, Part C.

End of Specification:

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