Johnson Controls York MaxE YK Series, Manual

Page: 115 / 139

JOHNSON CONTROLS
FORM 160.75-O1 (309)
16
system components description
general
The YORK Model YK MaxE
TM
Centrifugal Liquid
Chiller is completely factory-packaged including evapo-
rator, condenser, compressor, motor, lubrication system,
OptiView Control Center, and all interconnecting unit
piping and wiring.
compressor
The compressor is a single-stage centrifugal type pow-
ered by an open-drive electric motor.
The rotor assembly consists of a heat-treated alloy steel
drive shaft and impeller shaft with a cast aluminum,
fully shrouded impeller. The impeller is designed for bal-
anced thrust and is dynamically balanced and over-speed
tested. The inserted type journal and thrust bearings are
fabricated of aluminum alloy. Single helical gears with
crowned teeth are designed so that more than one tooth
is in contact at all times. Gears are integrally assembled
in the compressor rotor support and are film lubricated.
Each gear is individually mounted in its own journal
and thrust bearings.
The open-drive compressor shaft seal is a double bellows
cartridge style with ceramic internal and atmospheric
seal faces. The seal is oil-flooded at all times and is
pressure-lubricated during operation.
capacitY control
Prerotation vanes (PRV) modulate chiller capac-
ity from 100% to as low as 15% of design for
normal air conditioning applications. Operation
is by an external, electric PRV actuator which
automatically controls the vane position to main-
tain a constant leaving chilled liquid temperature.
compressor luBrication sYstem
(see fig. 6)
The chiller lubrication system consists of the oil pump,
oil filter, oil cooler and all interconnecting oil piping
and passages. There are main points within the com-
pressor which must be supplied with forced lubrication
as follows:
1. Compressor Drive Shaft (low Speed)
a. Shaft seal.
b. Front and rear journal bearings – one on each
side of driving gear.
c. Low speed thrust bearing (forward and reverse).
2. Compressor Driven Shaft (high Speed)
a. Forward and reverse high speed thrust
bearing.
b. Two journal bearings.
3. Speed increasing Gears
a. Meshing surfaces of drive and pinion gear teeth.
To provide the required amount of oil under the nec-
essary pressure to properly lubricate these parts, a motor
driven submersible oil pump is located in a remote oil
sump.
Upon pressing of the COMPRESSOR START switch
on the Control Center, the oil pump is immediately
energized. After a 50 second pre-lube period, the com -
pressor motor will start. The oil pump will continue to
run during the entire operation of the compressor, and
for 150 seconds during compressor coastdown.
The submerged oil pump takes suction from the sur-
rounding oil and discharges it to the oil cooler where heat
is rejected. The oil flows from the oil cooler to the oil
filter. The oil leaves the filter and flows to the emergency
oil reservoir where it is distributed to the compressor
bearings. The oil lubricates the compressor rotating
components and is returned to the oil sump.
There is an emergency oil reservoir located at the
highest point in the lubrication system internally in
the compressor. It provides an oil supply to the various
bearings and gears in the event of a system shutdown
due to power failure. The reservoir, located on the top of
the compressor, allows the oil to be distributed through
the passages by gravity flow, thus providing necessary
lubrication during the compressor coastdown.