Specification; Sound Standards; Compressor; Motor Starting - York YGWH 115 Installation, Commissioning & Operation

2. Specification

YGWH water cooled chillers are completely factory
assembled with all interconnecting refrigerant piping
and wiring ready for field installation.
The unit is pressure tested, evacuated, and fully
factory charged with refrigerant R134a and oil in the
independent refrigerant circuit. After assembly, an
operational test is performed with water flowing through
the heat exchanger to ensure that the refrigerant circuit
operate correctly.
YGWH units are designed and manufactured within an
EN ISO 9001 accredited organisation and in conformity
with the following safety standards:
• NB/T 47012
• GB/T18430.1
• GB25131
YGWH units are designed to work independently, or in
conjunction with other equipment via Modbus building
management systems or other automated control
systems.

Sound Standards

The sound data for YGWH water cooled chillers
conforms to, and is rated in accordance with ARI
Standard 575.

Compressor

A semi-hermetic screw compressor is provided
to ensure high operational efficiency and reliable
performance. Capacity control is achieved through
slide valve. The compressor is a positive displacement
type characterized by two helically grooved rotors,
which are manufactured from forged steel. The 50 Hz
motor operates at 2950 rpm to directly drive the male
rotor, which in turn drives the female rotor on a light
film of oil.
Each compressor is direct drive, semi-hermetic, rotary
twin screw type and includes the following items:
• two screw rotors, manufactured from forged steel;
• a cast iron compressor
machined;
• a discharge check valve can prevent rotor backspin
during shutdown;
• a suction vapour cooled, high efficient and reliable
semi- hermetic motor has overload protection:
thermistor and current overload protection.
EN
housing precisely
Form 6S6I-B01C-EOMA-EN (0318)
Refrigerant vapour is sucked into the void created by
the unmeshing of the male and female rotors. Further
meshing of the rotors closes the rotor threads to the
suction port and progressively compresses the vapour
in an axial direction to the discharge port. The vapour
is compressed in volume and increased in pressure
before exiting at a designed volume at the discharge
end of the rotor casing. Since the intake and discharge
cycles overlap, a resulting smooth flow of vapour is
maintained.
The rotors are housed in a cast iron compressor housing
precision machined to minimize the void between the
housing and the rotors. Contact between the male and
female rotor is primarily rolling on a contact band on
each of the rotor's pitch circle. It result in virtually no
rotor wear and increased reliability.
The compressor incorporates a complete anti- friction
bearing design for reduced power input and increased
reliability. Four separated, cylindrical, roller bearings
handle radial loads. Angular-contact ball bearings
handle axial loads. Together they maintain accurate
rotor positioning at all pressure ratios, thereby
minimizing leakage and maintaining efficiency.
Motor cooling is provided by refrigerant vapour from
the evaporator flowing across the motor. Over load
protection includes overheat and current overload
protections.

Motor Starting

Star/Delta (S/D) open transition starter is used for
compressor motor starting. The S/D starter utilizes 3
motor contactors and a starting relay. The starter allows
inrush current to be limited to approximately 33%LRA
for the first 4~10 seconds, with current changing to
normal running current when the Delta connection is
established

Capacity Control

The compressors should start at the minimum
load position and provide a capacity control within
25%~100% by using one continuous function slide
valve.
The capacity control valve regulating spring returns
the valve to the minimum load position to ensure
compressor starting at the minimum motor load.
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