Installation and operation manual
22
EWWD440~850AAYNNO**
Packaged water-cooled water chillers
4PW25558-1B
Set the thermo OFF temperature and differential temperature
on the graphic panel display.
[“MENU”
➞
“SETTING”
➞
“SETTING (1/2)”]
See
"Target temperature and low load stop related settings screen"
.
Figure: Unit operation between thermo OFF and thermo reset.
Target temperature and low load stop related settings screen
See
"How to change settings in the touch panel" on page 15
change the settings.
Please check the following first in case the unit repeats low
load stops frequently
1.
Cooling load is lower than the capacity control range of the unit.
Capacity control range is up to 25% of the full load capacity
condition as stated in the catalog.
This does not mean that the capacity control opening of the
compressor is 25%. However, in some cases, we take a liberty
of setting the minimum capacity control range to 25% or higher,
depending on the service conditions of the customer.
For further information, check the delivery specification.
2.
The holding water quantity is correct.
If the thermo differential setting in function of the holding water
quantity is extremely small, this may lead to the repetition of
frequent ON-OFF.
Possible solution is to increase the thermo differential setting
value on the graphic panel display "SETTING (1/2)” screen.
Further, if the holding water quantity is extremely low, frequent
ON-OFF of the unit is inevitable even though the adjustment of
settings has been done. This may largely affect the
airconditioning or cooling system process.
Check the minimum holding water quantity of this unit and make
sure that the system has a sufficiently important margin.
In case the system is equipped with a by-pass circuit, make sure
to add volume of the by-pass circuit to the minimum water
volume of the unit. For minimum holding water volume, see
Table 2: Minimum water volume on page 9
.
ON-OFF limiting function
Cooling of the compressor motor is performed by suction refrigerant
gas.
However, if the compressor repeats Run/Stop frequently, the cooling
effect of the suction refrigerant gas decreases and the motor coil
temperature of the compressor may increase excessively.
This function is set up to prevent the excessive increase of motor coil
temperature due to frequent Run/Stop of the compressor.
During ON-OFF limiting time, the compressor does not start. If the
compressor is requested to start during this period, the compressor
starts after count-up of the ON-OFF limiting time only.
ON-OFF limiting time is counted for each compressor individually.
Figure: How ON-OFF limiting time is decided.
Relationship between A, B, C and D
■
if A–C
≥
B
⇒
D=A–C
■
if A–C<B
⇒
D=B
Thermo OFF temperature and differential temperature in
case of models with the 2-temperature setting option have
influence on several operation modes.
1
Chilled water inlet temperature
2
Chilled water outlet temperature
3
Thermo OFF temperature default setting=1.0°C
4
Thermostat differential (default setting=3.0°C)
5
Unit stop [OPERATE/STOP monitor 2-88X]
6
Pump is operating
[Chilled water pump operation command 88WEX
Cooling water pump operation command 88WCX]
7
Operation restarts after timer count-up in case the ON-OFF
limiting timer was activated
1
Set the target temperature for chilled water outlet temperature.
2
Set the Thermo OFF temperature (default setting=1.0°C).
3
Set the thermostat differential temperature (default=3.0°C).
2
1
4
3
7
Thermo reset
temperature
Target temperature
Thermo OFF
temperature
Unit is operating
Unit stop (5)
Compressor is
operating
Compressor stop
Pump is
operating (6)
Pump stop
inlet
outlet
1
1
2
3
NOTE
■
This is the screen of models with the 2-
temperature setting option. For standard models,
the target temperature is represented by one line
only.
■
Touching any of the items will display a brief
explanation on the item (except for the target
temperature).
Compressor
Operation
Compressor
Stop
Compressor operating
time before stopping=C
ON-OFF
limiting
time=D
Time
Maximum ON-OFF limiting time: 600 seconds=A
Minimum ON-OFF limiting time: 180 seconds=B