Panasonic U-8ME1E8E Service Manual page 20

4. Output of PCB
4-4. Refrigerant balance valve [RBV]
The main purpose of this valve is to adjust the flow of refrigerant (refrigerant volume) in the indoor unit heat
exchanger at heating operation. When the valve determines that there are signs of excess refrigerant, refrigerant
is recovered at the receiver tank.
This valve also turns ON in order to recover refrigerant at the outdoor unit after heating operation is stopped.
* This valve is never turned ON at the same time with the RCV.
- This valve turns ON for 20 seconds after the system stops at heating mode, and then turns OFF.
- This valve turns ON once after the system starts at heating mode.
- This valve turns OFF when an abnormal drop in compressor discharge gas temperature is detected.
- This valve turns OFF when liquid back to the compressor is occurring.
Judgment of liquid back :
* After the valve turns from ON to OFF, it will not turn ON again for 15 minutes.
RCV
HP
RBV
LP
Receiver tank holds small amount of refrigerant
RCV
HP
RBV
LP
Refrigerant gas in the top of receiver tank is pulled into low pressure side.
4-5. Oil recovery valve [ORVR]
This valve is for recovering oil from the oil separator of its own outdoor unit or balance tube to the compressor of
its own outdoor unit.
- This valve turns ON when the oil level of the compressor is "0" or "1"
In this situation, system performs Self oil recovery control, Inter-outdoor unit oil recovery control, or system oil
recovery control.
- This valve turns ON for 2 minutes after the compressor starts.
- This valve is always OFF when outdoor unit is stopped
* For oil level of compressor, refer to "Oil Control" section.
4-6. By-pass valve [BPV]
This valve is for pushing the oil in the balance piping into other outdoor unit.
- This valve turns ON when the oil level of compressor is "2" or "1" in its own outdoor unit and the oil level of
compressor is "0" in other outdoor unit.
* This valve turns ON for ten seconds and turns OFF for 20 seconds. This operation is repeated while oil is
supplied to others.
* For more information on oil level of compressor, refer to "Oil Control" section.
Detected suction temperature is lower than low-pressure sensor temperature.
Difference between high-pressure sensor temperature and discharge temperature
of compressor is small. (less than 10 deg)
ON
Condenser
Liquid
flow
Over charge condition
Liquid flow
Condenser
Two-phase flow
Adequate condition
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2WAY SYSTEM
Control Functions-Outdoor Unit
Two-phase flow
1