York YS Service Manual download pdf (Page 40)

6.4 Normal Operation

After the compressor reaches its operating speed the

slide valve will begin to load, under the control of the

control Centre, based on the leaving chilled liquid

temperature. The unit capacity will vary to maintain the

leaving chilled liquid temperature at the programmed

setpoint. A drop in chilled liquid temperature will cause

the slide valve to unload to decrease unit capacity.

When the chilled liquid temperature rises, the slide valve

loads the compressor and increases the unit capacity.

The compressor motor current will be limited to a

programmable maximum during the unit operation. The

control centre can be programmed in various ways to

limit the motor current to between 40 and 100% of Full

Load Current as required (see the control centre

Operation Instruction for more details).

While the compressor is running a wide variety of

system parameters are monitored automatically by the

control centre. These can be accessed and displayed as

required via the control centre keypad and display. If any

problems are detected the cause will be shown on the

display and the appropriate action will be taken, eg

reducing slide valve loading, giving a warning message,

or shutting down the unit.

6.5 Shutdown

During normal operation the unit may shut down for a

number of reasons such as low load, scheduled daily

shutdowns and multi unit cycling. In each case the

control centre display will indicate the reason for the

shutdown. For example, if during operation the control

centre has unloaded the compressor completely and

load continues to fall, the unit will be shut down and the

display will read: DAY-TIME - LOW WATER

TEMPERATURE - AUTOSTART.

This occurs when the leaving water temperature falls to

2.2°C below setpoint or 2.2°C, whichever is higher.

"Autostart" indicates that the unit will restart

automatically if the water temperature rises again.

If the unit is shut down because a problem has been

detected by the control centre, a similar type of message

will be displayed indicating the nature of the problem

(see control centre Operation Instruction, for more

information).

When the unit is shutdown, the slide valve will close

automatically to minimise load on the compressor motor

during startup. A minimum of two minutes after

shutdown is required for system pressure equalisation

before the compressor will be allowed to restart.

6.6 Manual Shutdown

To stop the unit manually:

1. Push the COMPRESSOR "STOP/RESET" switch.

The control centre display will show: 2.0 MIN.

LOCKOUT DELAY. This prevents compressor

restart until system equalization is achieved.

2. Stop the chilled water pump (if not wired into the

control centre, in which case it will shut off

automatically.)

3. Open the switch to the cooling tower fan motors, if

used.

The compressor sump oil heater

(thermostatically controlled) is energised

when the unit is stopped.

6.7 Prolonged Shutdowns

If the unit is to be shut down for an extended period of

time (for example, over the winter season), the following

procedure should be followed:

1. If freezing temperatures are likely to be

encountered while the system is idle, carefully

drain the cooling water from the cooling tower,

condenser, condenser pump, and the chilled water

system, chilled water pump and cooler. Open the

drains on the cooler and condenser liquid heads to

assure complete drainage. If a Solid State Starter is

fitted drain water from starter cooling loop.

2. Move jumper J-57 on the microprocessor board to

the OFF position to conserve the battery (see

control centre Operation Instruction).

3. Open the main disconnect switches to the

compressor motor, condenser water pump and the

chilled water pump. Open the 115 Vac circuit to the

control centre.

To return the unit to operation is the reverse of this

procedure, however, after a prolonged shutdown it will

be necessary to replace all of the oil and install a new oil

filter element. This should only by done by suitably

qualified personnel.

6-2 035L02381-GB0

1 2 ... 35 36 37 38 39 40 41 42 43 44 45 ... 67 68

Comments to this Manuals

No comments

York YS Service Manual Page 40

Comments to this Manuals

Related products and manuals for Air compressors York YS