2. Control Functions
Control functions on the module
SMGB0097 rev.0 - 07/2015
18
2
Mode II
Mode II is used mainly for systems containing multiple chiller units, or those with variable flow. To avoid alteration of the
water temperature of the rest of chiller units in operation, the pump is operated with a low water temperature.
△
△
△
Load
Secondary
pump
Primary pump
Chiller
unit
Chiller
unit
a.
When outdoor temperature is under 2ºC
When outdoor temperature falls under 2ºC, the operation order of the pump is output, and the continuous operation
of the cold water circulation pump starts automatically. Here, when cold water temperature becomes higher than
5ºC, operation becomes intermittent, with the pump running for 5 minutes, then stopped during 55 minutes.
When cold water temperature rises even further, above 7ºC, the 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 II)
2
4
5
3
2
4
7
5
3
7
△
△
△
△
(a) When outdoor temperature is decreasing
(b) When outdoor temperature is increasing
Explanation of codes
Continuous pump operation
Intermitent pump operation
5 minutes run
55 minutes stop
× Pump stop
→ Change trend of cold water
temperature
More than
Less than
More than
Less than
More than
Less than
More than
Less than
More than
Less than
More than
Less than
W
ater
temperature
(ºC)
W
ater
temperature
(ºC)
N O T E
When the outdoor temperature of the cold water circulation system is lower than that of the installation place of the
chiller unit itself, then it is necessary to install a separate outdoor temperature thermostat in the place with the lowest
temperature, and connect it in parallel with the operation order circuit of the pump.
