York YS Service Manual download pdf (Page 39)

6 OPERATION

If the oil heater is de-energised during a

shutdown period, it must be energized for 24

hours prior to starting the compressor.

6.1 General

YS chillers are designed to work independently, or in

conjunction with other equipment via a York ISN

building management system or other automated

control system. The compressor can be started and

loaded as required using a range or input signals to

achieve the desired cooling effect. This section

describes the normal procedures for operation of the

unit and should be read in conjunction with the control

centre Operation Instruction.

6.2 Pre-Startup

Prior to starting the chiller, observe the control centre.

Make sure the display reads SYSTEM READY TO

START.

The internal clock, all the control setpoints and any other

required settings, eg., daily schedule, should be

programmed before the unit is started. (Refer to Control

Centre Operation Instruction).

If the chilled water pump is manually operated, start the

pump, the control centre will not allow the unit to start

unless chilled liquid flow is established through the unit.

If the chilled liquid pump is wired to the control centre the

pump will automatically start.

6.3 Start-up

1. To start the chiller, press the compressor START

switch. This switch will automatically spring return

to the RUN position. When the start switch is

energised, the control centre is placed in an

operating mode and any fault will be shown by a

display message.

Any faults which occur during STOP/RESET

are also displayed.

The slide valve is returned to the unload

position automatically when the unit is shut

down to prevent loading the compressor on

start-up.

When the unit starts, the following automatic sequences

are initiated: (Refer to Figure 6.1 Starting & Shutdown

Sequence).

1. The control centre display message will read

SYSTEM START SEQUENCE INITIATED for the

first 30 seconds of the starting sequence.

2. The measured oil and evaporator pressures are

compared during system equalization so that any

offset is stored for use in calculating deferential trip

points during compressor operation.

3. The chilled liquid pump contacts close starting the

chilled liquid pump to allow liquid flow through the

cooler. The chilled water flow switch is bypassed

for the first 25 second of the start sequence.

4. After 30 seconds of start sequence operation, the

compressor will start. While the motor is

accelerating to full speed the control centre display

will read: SYSTEM RUN - CURRENT LIMIT IN

EFFECT.

5. When the motor reaches full speed and the current

falls below 100% FLA the message will read:

SYSTEM RUN - LEAVING TEMP. CONTROL.

6. The anti-recycle timer begins after the 30 seconds

of pre-run time. The timer will run for 30 minutes

after the compressor starts. If the unit shuts down

during this period of time it cannot be started until

the timer completes the 30 minute cycle.

For display messages and information

pertaining to operation, refer to the control

centre Operating Instruction.

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York YS Service Manual Page 39

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