Discharge Temperature; Sub Cooling Degree; Liquid Refrigerant Flood Back; Suction Accumulator - Panasonic 4CW056MA01 Applications Manual

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It is necessary to keep the proper superheating degree since too high superheating will cause the high
discharge temperature and the decrease of refrigerant mass flow rate.

2.3 Discharge Temperature

Panasonic C-SW series compressor is with high pressure shell structure. Motor is cooled down by discharge
gas. The discharge temperature shall be controlled lower than the limitation in the compressor specification.
The recommended discharge temperature is not higher than 95℃ under standard conditions. And under
overload condition, shall not exceed 115℃. Discharge temperature is measured in the copper pipe on the
end cap of compressor.

2.4 Sub Cooling Degree

The sufficient sub cooling degree can not only increase the cooling and heating capacity but also can keep
the inlet of expansion valve or capillary full of liquid state refrigerant.
On the contrary, the insufficient sub cooling will cause flash gas occurring at the inlet of expansion valve,
which will result in capacity reduction and increasing vibration, noise.

2.5 Liquid refrigerant flood back

Liquid refrigerant flood back can cause great influence to the reliability of compressor. When liquid
compression, knocking noise, current surge, or undesirable vibration etc. occurs, implement the following
countermeasures to prevent liquid refrigerant flood back.
1) Add suction accumulator
2) Decrease refrigerant charge amount
3) Change the operation mode
Install an internal heat exchanger.
Observe with the compressor with sight glasses supplied by Panasonic, and consult your account
representative for the result.

2.6 Suction Accumulator

A suction accumulator is necessary to prevent the uncontrolled liquid flooding back.
The proper size suction accumulator can:
1) Prevent liquid refrigerant migrating to compressor
2) Prevent liquid refrigerant being sucked into compressor.
The suction accumulator used in the system should at least meet the requirements as follow:
1) The size of the accumulator must be greater than 60% total refrigerant volume.
2) To ensure well oil return, a φ1.5~2.3 mm orifice is necessary in the suction accumulator.
3) Filter mesh must be used to prevent orifice being blocked when orifice is smaller than φ2.0 mm
See a cutaway view of suction accumulator in Figure2-1


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