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A Series Inverter Modular Air-cooled Chiller (Heat Pump)
7.12 Freeze protection
When the flow passage of the shell-and-tube heat exchanger is frozen up, it would cause serious
damage to the heat exchanger, such as cracking and leakage which are out of warranty, therefore, the
user should take measures stated below for freeze protection:
(1) In order to make sure the unit can automatically perform defrosting under low temperature, the
water pump must be interlocked with the unit.
(2) Under subzero condition, when the unit is required to perform cooling, anti-freeze liquid should be
added into the water system based on the table below.
(3) Under subzero condition, when the unit is not required to perform cooling for a short term, the
unit should be powered on; when the unit is not required to perform cooling for quite a long term,
disconnect the power supply and then drain the shell and tube completely.
Thermal and physical properties of the glycol solution
Quality concentration Initial freezing temperature Density
16 -7 1020
19.8 -10 1025
23.6 -13 1030
27.4 -15 1035
31.2 -17 1040
35 -21 1045
38.8 -26 1050
42.6 -29 1055
46.4 -33 1060
Notes:
(a) This table is cited from
Design Manual for Practical Refrigeration Engineering
published by China
Architecture Industry Press. If physical data of the glycol has been provided by the manufacturer, it
always prevails.
(b) Once the glycol is taken as the second refrigerant, its initial freezing temperature of the glycol
solution should be 2~3°C lower than the lowest environment temperature.
7.13 Routine maintenance
Routine maintenance shall be performed periodically by the qualied technician so as to extend the
service life of the unit and lower the possibility of occurrence of faults. Record weekly the running status
of the unit to facilitate troubleshooting for the servicemen.
■ Daily Maintenance
(1) Check the circulating water pump and the ow rate.
(2) Check the voltage and power supply.
■ Weekly Maintenance
(1) Check the main unit, like if the compressor runs with abnormal noise, if the distribution box is
attached securely and if the pipeline generates abnormal vibration or leakage.
(2) Record key parameters, like pressure, pressure etc.
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