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2WAY SYSTEM
Control Functions - Outdoor unit
1
4. Special Control
4. Special Control
2WAY VRF SYSTEM
Control Functions
7-1. Type of Electronic control valves
7-2. Power Initialization
MOV1 : For upper side heat exchanger
MOV2 : For lower side heat exchanger
If no indoor units have started (even once) after the power supply to the outdoor unit, the MOV holds the 480
pulses (fully open).
7-3. Control of Electronic control valves
Electronic control valves for heat exchanger control according to the operation mode.
Cooling
Heating
Mode of system
Compressor
MOV1 (pulse)
MOV2 (pulse)
Stop
Stop
0
0
Operation
480
480
Stop
0*
1
0*
1
Operation
0 ~ 480*
2
0 ~ 480*
2
Stop
0
0
* When the indoor unit receives the signal for operation request from the control equipment, the pulse turns
other than the 480 pulses (regardless of the thermostat ON/OFF or operating ON/OFF).
It is necessary to switch ON the power supply again if the 480 pulses are required.
*1 However, 100 pulses remain for 2 minutes after all systems stopped.
*2 If any one compressor in the outdoor unit is operating at heating mode, electronic control valves perform SH
control.
SH control adjusts the difference of temperature between the liquid and gas temperature to 1 ~ 5 degrees
Celsius.
(7) Electronic Control Valves [MOV1, MOV2]
2WAY VRF SYSTEM
Control Functions
4. Special Control
(8) SC Circuit Electronic Control Valve [MOV4]
During cooling operation, the liquid refrigerant which condenses at the outdoor unit heat exchanger flows into
the receiver tank, and SC (sub-cool = super-cooling) approaches 0 degree.
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 significantly.
To prevent this trouble from occurring, MOV4 operates so as to increase super-cooling in the double tube coil.
8-1.
(9) Crankcase Heater Control [CH1, CH2]
When the compressor stops, the crankcase heater of its own compressor is turned ON in the following conditions.
Cooling SC Control
8-2. Heating SC Control
When the discharge temperature increases
to 90°C or more, MOV4 opens to 100 pulses
to cool down the compressor.
Then, the MOV4 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 85°C or less.
8-3. Discharge Temperature Control of Compressor
MOV4 controls the difference of temperature between the SCG thermistor and low pressure saturated
temperature to 3 ~ 5 degrees Celsius.
Thermistor (SCG)
MOV4 (Discharge temperature control of compressor)
Liquid refrigerant
returns to accumulator.
Liquid refrigerant
Does not fully evaporate,
resulting in liquid back-up.
Liquid refrigerant
When the outdoor air temperature ≤ 20°C
When the discharge temperature ≤ the outdoor air tempe 15°C
When the compressor stops and 30 minutes later.
For the type of 18HP and 20HP units, if the MOV1 or MOV2 opens more than 300 pulses, the MOV4 may
occasionally open between 100 and 350 pulses.
* The type of 8HP to 16HP units are not functioned.
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16/08/26 19:23:16
