SINGLE SCREW CHILLERS IMM
Engineered for Flexibility and Performance
29
8. Functions of Chiller
8.1 Automatic control of water-temperature for the chillers
The single screw chiller utilizes PID control so that ELWT is automatically close to setting value.
Compressors utilize the stepless control to adapt cooling load change to ensure constant ELWT in
a short time.
The logic diagram between ELWT and compressor capacity is shown below:
Loading
remaining
Unloading
△
t=0.1
℃
ELWT Setting
Default 7
℃
ELWT Curve
Loading/Unloading
△
t=0.1
℃
remaining
remaining
Loading
Fig.8-1
Notes:
Cooling condition:
the leaving water temperature showing in the figure above is chilled water
temperature. The figure above just indicates the chiller capacity control ability along with
fluctuation of the chilled outlet-water temperature, and the capacity control may be more complex
under the user standard.
Heating condition:
the leaving water temperature showing in the figure above is cooling
outlet-water temperature. The figure above just indicates the chiller capacity control ability along
with fluctuation of the cooling outlet-water temperature, and the capacity control may be more
complex under the user standard.
8.2 Chiller capacity control under low cooling load
While the cooling load is below the chiller minimum load, the leaving water temperature of chilled
water will fall progressively.
While the water temperature falling to “setting value of the leaving water temp + stop temperature
difference”, the chiller will be automatically shut down, while the water temperature rising to “set
value of leaving water temperature + stop temperature difference”, the compressor will start to
operate automatically again. (The compressor is configured with no re-start function within
start/stop time limit)
While the chiller frequently stops at low water temperature, please confirm the items below:
a. Whether the cooling load falls within the range of capacity control.
Cooling load that is below the chiller minimum capacity will lead to frequent start/stop of the
chiller.
b. Whether there is a proper water flow in the equipment