2WAY SYSTEM
Control Functions
-
Outdoor Unit
1
- 14
1
4. Output of PCB
4-7. Refrigerant interception valve [O2*]
*O2 valve is the local supply parts.
This valve works when the outdoor unit receives signal of the refrigerant leakage from the indoor unit.
The indoor unit that transmits the signal of the refrigerant leakage gives “P14”alarm.
To activate this function, it is necessary to set it to EEPROM on the main outdoor PCB and indoor PCB.
EEPROM setting in main outdoor unit
CODE: C1
Setting No.
Setting No.
0
0
1
1
2
This function invalid (factory preset mode)
This valve is turned OFF when the system is normal.
This valve is turned ON when the outdoor unit receives signal from the indoor unit.
This valve is turned ON when the system is normal.
This valve is turned OFF when the outdoor unit receives signal from the indoor unit.
EEPROM setting in indoor unit
CODE: 0B
Function of EXCT plug short-circuit
Indoor unit does thermostat OFF
(factory preset mode)
Indoor unit gives “P14”alarm and transmits the refrigerant leakage signal.
4-8. MOV for heat exchanger [MOV1, MOV2]
4-8-1. Type of Motor Operated Valves
Outdoor unit Capacity
8HP
10HP
12HP
14HP 16HP 18HP 20HP
MOV1
For heat exchanger in upper row For left side heat exchanger
MOV2
For heat exchanger in lower row For right side heat exchanger
4-8-2. Power Initialization
If no indoor units have started (even once) after the power supply to the outdoor unit, the MOV for heat
exchanger holds the pulse at 480 pulses.
4-8-3. Operation of MOV for heat exchanger
MOV operates according to the mode of indoor unit.
Mode of system Stop
Cooling
Heating
Compressor
Stop
Stop Operation
Stop
Operation
MOV 2 (pulse)
0
0
480
0
0 - 480
MOV 1 (pulse)
0
0
480
0
0 - 480
*If any one compressor in the outdoor unit is operating at heating mode, both MOVs perform SH control of heat
exchanger.
SH control adjusts the difference between the liquid temperature and gas temperature to -1 - 5 degree.
3WAY SYSTEM
Control Functions
4. Output of PCB
4-9. SC Circuit Electronic Control Valve [MOV4]
4-9-1. SC Control (Cooling Mode only)
During cooling operation, the liquid refrigerant which condenses at the outdoor unit heat exchanger flows into
the receiver tank, and SC (sub-cool = supercooling) approaches 0°C. When SC is small and the length of the
tubing connecting the indoor and outdoor units is long, the refrigerant flow in the indoor unit will be reduced sig-
nificantly. To prevent this trouble from occurring, MOV4 operates so as to increase supercooling in the double
tube coil near the outlet of the outdoor unit.
In addition, MOV4 controls refrigerant flow volume so that it will not flow back to the compressor in the liquid
state. SH in suction that is difference between the SCG temperature and low pressure sensor temperature is
adjusted to 3-5°C.
4-9-2. Discharge temperature control of compressor
When the discharge temperature increases to 95°C or more, MOV 4 opens to 100 pulses to cool down the
compressor. MOV 4 operates according to the state of the discharge temperature between 20 - 480 pulses. This
operation takes priority over SC control.
This operation is continued until discharge temperature decreases to 80°C or less.
4-10. Crankcase Heater Control [CH1, CH2
, CH3
]
When the compressor stops, the crankcase heater of its own compressor is turned ON.
Liquid
(SC=0deg)
Liquid
(Large SC)
MOV4
(SH control)
Gas returns to
accumulator
Refrigerant on the inner side evaporates,
cooling the liquid refrigerant on the outer side.
SCG
(Discharge temperature control of compressor.)
Liquid returns to
accumulator
Does not fully evaporate,
resulting in liquid back-up.
Liquid
Liquid
MOV4
SCG
SM830204-05_2WAY SYS.indb 14
2015/01/21 17:00:00
Summary of Contents for U-20ME1E81
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