Panasonic U-8MF2E8 Service Manual page 23

4. Output of PCB
4-4. Refrigerant Balance Valve [RBV]
The main purpose of this valve is to detect the flow of refrigerant (refrigerant volume) on the indoor unit when the
outdoor unit heat exchanger is functioning as an evaporator.
When the valve determines that there are signs of excess refrigerant, refrigerant is recovered at the receiver tank.
This valve is ON during heating operation and when the outdoor unit heat exchanger is functioning as an evaporator
during mixed heating/cooling operation. It also turns ON in order to recover refrigerant at the outdoor unit after
heating operation is stopped.
* This valve is never ON at the same time as 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:
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 5 degrees)
* 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.
ON
Condenser
Liquid
flow
Over charge condition
Liquid flow
Condenser
Two-phase flow
Adequate condition
1 - 15
3WAY SYSTEM
Control Functions
Two-phase flow
1