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3.4
Low Load Control
Chilled water temperature, hot water temperature and solution flow rate are controlled by the way
mentioned above and the chillerheater keeps on efficient and stable operation from full load to low
load. When the load of chilled water or that of hot water goes down under the set point, the gas
control valve closes to stop the operation of the chillerheater. This action is called "Low load stop".
This action is made by the thermostat installed at the outlet of chilled water or hot water. Further,
when the chilled water or hot water temperature reaches the operating range, the chillerheater will
begin to operate automatically again.
Chilled water
thermostat
OFF
Hot water
Thermostat
OFF
3.5
Emergency Stop
When the chiller-heater falls in any unfavorable condition for operation due to external cause, the
main gas valve closes automatically to stop operation of the chiller-heater. Refer to the Table 3.1
List of Protective Devices for detail stop of operation.
3.6
Protective Devices
When the chiller-heater is detected to be abnormal in pressure, temperature, etc., the machine is
forced to stop the operation of the functional parts such as pumps, a fuel control valve and so on
and to actuate protective devices. Besides, when crystallization begins temporarily, the de-
crystallizing system actuates automatically to prevent from crystallization.
The actuating conditions and safety action of the protective devices are shown in the Table 3.1
Dilute operation
(approx, 20
minutes)
Damper low
combustion
position
High pressure generator
Solution temp. below rated
value
Fig.3.3 Low Load Stop Flow Diagram (Cooling)
Dilute operation
(approx, 20
minutes)
High pressure generator
Solution temp. below rated
value
Fig.3.4 Low Load Stop Flow Diagram (Heating)
Solution
Pump
STOP
Main gas
Valve
CLOSE
Solution
Pump
STOP
19
Refrigerant
Pump
STOP
Refrigerant
Pump
STOP
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