EN - 37
EN - 36
ENGLISH
Adjustment during Operation
Adjusting Refrigerant Quantity of the Refrigeration Unit
During determination of refrigerant quantity, temperature setting of all Unit coolers/Display cases needs to be set to the
lowest temperature without activation of the thermostat for making the refrigeration unit operating continuously.
(1) Method of determining refrigerant quantity
Check the operation condition of the refrigeration unit by the following method, and adjust the refrigerant quantity
to the appropriate value according to Table 3 (Determination criteria of refrigerant quantity).
1) Check that the suction gas temperature is 18°C or below.
2) Check that the superheat of the suction gas temperature is 10 K or greater.
3) Check if the high pressure has been set to the standard high pressure (Table 2).
4) Check if the gas cooler outlet temperature is +2 K to +5 K for the ambient temperature.
The method of checking each temperature and pressure should comply with Table 1 and the value should be
confirmed with the digital display.
Caution
Table 1 Method of checking each temperature and pressure
Reference item
DIP switch
SW13
Rotary switch
(knob) SW 11
Suction gas
temperature
SW13-2 ON
(all other OFF)
SUC
High pressure
SW13-2 ON
(all other OFF)
PRESSURE
Gas cooler outlet
temperature
SW13-2 and 7 ON
(other OFF)
OFF
(Press ▲ 3 times)
Table 2 Standard high pressure
Ambient
temperature
Evaporating
temperature
<
-20°C
Evaporating
temperature
>-20°C
High pressure
High pressure
0 °C or below
3.4MPa
3.4MPa
5 °C
3.9MPa
3.9MPa
10 °C
4.4MPa
4.4MPa
15 °C
5.0MPa
5.0MPa
20 °C
5.6MPa
5.8MPa
25 °C
7.5MPa
8.0MPa
30 °C
8.5MPa
9.0MPa
35 °C
9.1MPa
9.6MPa
Table 3 Determination criteria of refrigerant quantity
Gas cooler outlet
temperature
High pressure
Less than “Ambient
tempe2 K”
“Ambient tempe2 K”
to
“Ambient tempe5 K”
Greater than “Ambient
tempe5 K”
High
▲
▲
Standard
Low
▲: Refrigerant overcharge, : Appropriate, : Refrigerant shortage,
: Perform continuous operation and monitor the condition.
(2) Refrigerant quantity adjustment
1) Shortage of refrigerant (when charging additional refrigerant)
• Perform cooling operation and charge additional refrigerant via the access port of the low pressure service
valve.
• Adjust valve opening during slow charging operation to avoid frosting beyond the refrigerant service valve.
• Guideline of charging rate of refrigerant is 20
g
per 5 seconds.
Note
: Rapid refrigerant charging may lead to a compressor failure.
2) Overcharging of refrigerant (when releasing the refrigerant)
• Release the refrigerant via the access port of the low pressure service valve.
• Open the valve very slowly. Use caution for oil leak out.
• As CO
2
refrigerant is heavier to air, use caution for gas stagnation.
3) After completing refrigerant adjustment, close the access port of the low pressure service valve.
Shortage of refrigerant tends to cause lower level of high pressure and higher level of intermediate
pressure.
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