Equipment Overview; Compressor; Capacity Control; Lubrication System - York YK Manual

Equipment Overview

JOHNSON CONTROLS
YORK YK chillers are completely factory-packaged including the evaporator, condenser,
®
compressor, motor, lubrication system, control center, and all interconnecting unit piping
and wiring.
The initial charge of refrigerant and oil is supplied for each chiller. When the optional con-
denser isolation valves are ordered, most units may ship fully charged with refrigerant and
oil. Actual shipping procedures will depend on a number of project-specific details.
The services of a Johnson Controls factory-trained, field service representative are in-
curred to supervise or perform the final leak-testing, charging, the initial start-up, and
concurrent operator instructions.

COMPRESSOR

The compressor is a single stage centrifugal type, powered by an open drive electric mo-
tor. The casing is fully accessible with vertical circular joints and fabricated of close grain
cast iron. The complete operating assembly is removable from the compressor and scroll
housing.
The rotor assembly consists of a heat treated alloy steel drive shaft and impeller shaft with
a high strength, cast aluminum alloy, fully shrouded impeller. The impeller is designed for
balanced thrust and is dynamically balanced and overspeed tested for smooth, vibration
free operation. Each impeller receives a special finishing treatment that improves aerody-
namic performance.
The insert-type journal and thrust bearings are fabricated of aluminum alloy and are
precision bored and axially grooved. The specially engineered, single helical gears with
crowned teeth are designed so that more than one tooth is in contact at all times to pro-
vide even distribution of compressor load and quiet operation. Gears are assembled as
part of the compressor rotor support and are film lubricated. Each gear is individually
mounted in its own journal and thrust bearings to isolate it from impeller and motor forces.

CAPACITY CONTROL

Pre-rotation vanes (PRV) modulate chiller capacity from 100% to 15% of design for nor-
mal air conditioning applications. Operation is by an external, electric PRV actuator which
automatically controls the vane position to maintain a constant leaving chilled liquid tem-
perature. Rugged airfoil-shaped, cast-manganese-bronze vanes are precisely positioned
by solid vane linkages connected to the electric actuator.

LUBRICATION SYSTEM

Lubrication oil is force-fed to all bearings, gears and rotating surfaces by a variable speed
drive pump which operates prior to startup, continuously during operation and during
coastdown. A gravity fed oil reservoir is built into the top of the compressor to provide
lubrication during coastdown in the event of a power failure.
An oil reservoir, separate from the compressor, contains the submersible oil pump, 2 HP
(1.5 kW) pump motor and 3000 watt immersion type oil heater. The oil heater is thermo-
statically controlled to remove refrigerant from the oil.
FORM 160.75-EG1 (519)
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