Panasonic 4CW056MA01 Applications Manual page 19

Table 3-2 Low Pressure Switch Setting
Refrigerant
The temperature in the scroll set and motor will rise rapidly due to loss of refrigerant charge. The low-pressure
switch will react upon low pressure occurs in the system. Sometimes, the low-pressure switch will react in
priority to the action of discharge thermostat or motor protector when the large amount of refrigerant leaks in
the short time.
Do not operate the compressor in exceeding 30 seconds when running under 0.03MPa (G).
Crankcase Heater
4)
The refrigerant is usually gathering in coldest point within the system during OFF cycle and the compressor
might become the right one where most of liquid refrigerant centralized.
After a long OFF cycle, the refrigerant vapor may condense into compressor oil, when compressor restarts.
the liquid refrigerant mixed with oil in foam status will lead to lubrication failures. The liquid refrigerant
migration is also the cause of low insulation resistance of compressor.
Panasonic recommends crankcase heaters should be used for the system with high refrigerant charge
volume. The crankcase heater of suitable power should remain the temperature of compressor bottom shell
11K higher than ambient temperature or reduce the oil level to specified level after 5 hours energizing.
The crankcase heater must be energized for a minimum of 5 hours prior to starting compressor.
High-Pressure Switch
5)
Panasonic scroll compressors require a high-pressure switch in order to protect the compressor during
blocked fan or fan failure conditions. The recommended settings are shown in Table 3-3
Table 3-3 High Pressure Switch Setting
R407C 7.3 psig (0.05MPa G)
R410A 22 psig (0.15MPa G)
R134a 4.3 psig (0.03MPa G)
Refrigerant
R407C
R410A
R134a
Cut-Off setting
Cut-Off setting
464 psig (3.2MPa G)
602 psig (4.15MPa G)
348 psig (2.4MPa G)
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