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2. Control Functions
Control functions on the module
SMGB0097 rev.0 - 07/2015
17
2
2.1.7 Anti-Freezing Control for Winter
When operation is stopped during winter, the temperature of cold water decreases and may induce freezing of the water-
side heat exchanger or the piping system. The outdoor temperature and cold water temperature are detected, to operate
the cold water circulation pump automatically, and protect the chiller unit from freezing.
There are 2 modes to define the run/stop conditions of the cold water circulation pump. Select the most appropriate mode
depending on the system structure and usage purpose.
1
Mode I (Factory default)
Mode I is used mainly for systems composed of 1 chiller unit, or those with fixed flow. Since the entire water circuit is
protected, the cold water pump is operated from a comparatively high water temperature.
Example of system where Mode I is recommended
3-Way Valve
△
△
△
△
Chiller
unit
Load
Cold water
circulation pump
a.
When outdoor temperature is under 2ºC
When outdoor temperature falls under 2ºC, the operation order of cold water circulation pump is output, and the
continuous operation of the cold water pump starts automatically. Here, when cold water temperature becomes
higher than 15ºC, operation becomes intermittent, with the pump running for 5 minutes, then stopped during 55
minutes.
When cold water temperature rises even further, above 25ºC, the cold water circulation pump operation
order output is set to OFF.
b.
Automatic release of anti-freezing operation
This operation is released when outdoor temperature becomes higher than 4ºC.
Explanation diagram of automatic operation control of the pump to prevent freezing in winter (Mode I)
Ex
planation of codes
Continuous pump operation
Intermitent pump operation
× Pump stop
→ Change trend of cold water
temperature
5 minutes run
55 minutes stop
(a) When outdoor temperature is decreasing
(b) When outdoor temperature is increasing
15
10
2
4
15
10
2
4
25
25
△
△
△
△
W
ater
temperature
(ºC)
W
ater
temperature
(ºC)
More than
Less than
More than
Less than
More than
Less than
More than
Less than
More than
Less than
More than
Less than