Provide NEMA Class B insulated polyphase motors, normal torque and starting
current, Design B, high efficiency squirrel-cage induction type, except as
otherwise specified. Provide Nema Design Class C when high starting torque
is required. [Provide [one] [two] -winding type two-speed polyphase
motors.] Nameplate for polyphase motors shall include efficiency index
letter. Motor duty requirements shall allow for maximum frequency
start-stop operation and minimum encountered interval between start and
stop. Motor torque shall be capable of accelerating the connected load
within 20 seconds with 80 percent of the rated voltage maintained at motor
terminals during one starting period. Provide [open drip-proof] [totally
enclosed] [explosion-proof] motor enclosures. Polyphase motor bearings
shall be double-shielded, grease lubricated, antifriction type with
provisions for radial and thrust loads as imposed by application duty.
Provide bearings with grease supply fitting and grease relief to outside of
enclosure. Single phase motor bearings shall be as specified for polyphase
motors, except manufacturer's standard prelubricated, sealed cartridge
types are acceptable. Provide [across-the-line magnetic] [reduced voltage]
type motor startersconforming to NEMA ICS 1 and NEMA ICS 2.
2.9
POWER TRANSMISSION COMPONENTS
Fan and open compressor drives shall be [direct] [and] [V-belt] type as
specified or indicated. Provide drives in accordance with the
manufacturer's published recommendations, except as otherwise specified.
Base horsepower rating of V-belt drives on maximum pitch diameter of
sheaves. Provide compressors with fixed sheaves and drives with a minimum
service factor of [1.5] [2.0]. Drives with motors rated up to and including
7 1/2 kW 10 horsepower shall be classical belt section, adjustable sheave
type, with a service factor of not less than 1.5. Drives with motors rated
over 7 1/2 kW 10 horsepower [up to and including 22 3/8 kW 30 horsepower,]
shall be classical section, adjustable sheave type with a service factor of
not less than 1.5. Where the number of unit starts exceeds 8 per 24 hours,
add 0.1 to the required drive service factor. Provide statically and
dynamically balanced sheaves, machined ferrous metal, bushing type, secured
by key and keyway. Pitch diameter of fixed pitch sheaves and adjustable
sheaves, when adjusted to specific limits, shall be not less than that
recommended by NEMA MG 1. Select adjustable sheaves to provide the
required operating speed with the sheave set at mid-point of its adjustment
range. The adjustment range for various size and type belts shall be 16
percent minimum for classical section belts and 12 percent minimum for
narrow section belts. Provide belt drive motors with slide rail or
equivalent adjustable motor bases. Provide manufacturer's standard direct
drive couplings for motors rated less than 2 1/4 kW 3 horsepower. For 2
1/4 kW 3 horsepowerand greater, direct drive couplings shall be
elastomer-in-shear type.
2.10
ALARM SYSTEM
Provide both audible alarms and trouble lights to indicate when an abnormal
condition exists in each room. Locate pushbuttons inside each room and
adjacent to door. Alarm bell shall be located outside of each refrigerated
room and adjacent to door. Each refrigerant room having electric defrost
shall be provided with a defrost compensator which shall deenergize the
abnormal condition alarm system during the defrost cycle; these devices
shall be coordinated with defrost time clock on the respective compressors.
Systems shall detect a temperature rise above the designated temperature
or actuation of entrapment pushbutton and shall energize an alarm lamp and
horn at cooler local alarm panel.
SECTION 15602N
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