Mini VRF SYSTEM
Control Functions - Outdoor unit
1 - 4
1
2. Compressor Control
2WAY VRF SYSTEM
Control Functions
3. Compressor Control
Once a compressor stops, it will not start for a period of 3 minutes (3-minute forced OFF).
However, this is not applied when the compressor was forced to stop as the result of a special control
operation. (Start control, Defrost control, Refrigerant oil recovery control, etc.)
(3) Forced Stopping of Compressor
(4) Capacity Control of Compressor (Roadmap Control)
Capacity control of compressor (start & stop of compressor and increase & decrease of inverter frequency)
are controlled according to the numerical value of the pressure sensor installed at the outdoor unit and the
temperature sensor installed at the indoor unit heat exchanger.
* The pressure detected by the pressure sensor is converted to the saturated temperature.
High pressure saturated temperature is converted from values detected by the high pressure sensor.
Low pressure saturated temperature is converted from values detected by the low pressure sensor.
1
This control is performed every 30 seconds.
* In the case that the compressor is stopped from such as special controls, load level does not turn to “0”
even if the indoor unit is most likely to be in stopped state.
Definition of evaporation temperature (Te)
Lowest temperature of all indoor units’ evaporation temperature (E1, E3) in the system including the
stopped indoor units
Definition of condensation temperature (Tc)
Outdoor units’ high pressure saturated temperature
Load level varies from a minimum of 0 to a maximum of 30 on 1 to 1 basis up to 31 levels.
When the indoor unit stops (including thermostat OFF), the level shows “0”.
In the case of test run mode, the actual level implies “30” even if a PC monitor indicates “31”.
Load level increases when the differential temperature noted above indicates plus (+) value and
decreases when it indicates minus (-) value.
However, the types of units which are set to control the discharge temperature vary according to the
lowest value from the intake temperature difference and discharge temperature difference.
The indoor unit demand level varies according to the following 2 conditions.
Te target and Tc target are controlled by the maximum value of all indoor units load level.
Intake temperature difference:
Difference between indoor unit remote control set temperature and intake temperature (TA)
Discharge temperature difference:
Difference between preset discharge setting temperature according to the type of indoor unit and
actual discharge temperature (TF)
2
When cooling operation, evaporation temperature (= antifreeze control) and condensation temperature
(= high pressure prevention control) are applied.
When heating operation, condensation temperature (= high pressure prevention control) is applied.
3
Compressor capacity can increase
6.5+ α
Compressor capacity
cannot increase
Compressor capacity decreases
Max. load level
15
0
6.0 + α
3.0 + α
deg
2.5+ α
Te_tgt_max. 6.0+ α
Te_tgt_min. 3.0+ α
16.0
unit: °C
13.0
30
11.0 + α/2
8.0 + α/2
Area B
Area C
Area A
Evaporation temperature area
3. Compressor Control
2WAY VRF SYSTEM
Control Functions
4-1. Evaporation temperature (= Te) control
The cooling capacity is adjusted with this control. It prevents freezing of the indoor unit heat
exchanger and the dew to the outside panel of the indoor unit. The capacity is adjusted according
to the following figure.
If the test run is continued for a long time, the mist may occur but it is not abnormal.
*
If more than 1 indoor unit is in test run mode, the evaporation temperature control is not applicable.
Once the indoor unit is selected for the test run, the thermostat will not be turned OFF.
After the last indoor unit is operated in the test run mode, the test run is automatically cancelled
after 1 hour.
4-2. Condensation Temperature Control
Target temperature of the Area B is different between cooling and heating operation.
In Cooling Mode
The purpose of this control at cooling
is to prevent abnormal high-pressure.
1
The evaporation temperature area changes depending on the maximum load level in each indoor
unit as shown on previous page.
The Area C is regarded as Area B for 6 minutes after compressor starts.
If outdoor temperature ≥ 15°C, α is enable.
Minimum α is enable in all indoor units.
If outdoor temperature < 10°C, α is disable.
Outdoor
temperature
α is enable
α
2
5
3
Indoor unit type
α : Correction Value of Te
Type D1, L1
Type P1, R1
Indoor units inapplicable to Gr 1, Gr 2
Gr 1
Gr 2
Gr 3
α is disable
start
15°C
10°C
Test run mode in cooling operation is used when the room temperature is low and the indoor unit
thermostat is not turn ON. This mode is used for operation check when the outdoor unit is fully
operated or additional refrigerant charge without stopping the system.
When the system operates in a minimum capacity, the system will continue operating for at least
6 minutes if the evaporation temperature area is Area C.
During special controls such as defrosting or oil recovering between the systems, the compressor
capacity will not be controlled by the evaporation temperature control area.
If the outdoor unit is stopped while the evaporation temperature is in Area C, the system may
operate from the lower compressor capacity when starting next time.
Test run mode
In Heating Mode
Heating capacity is adjusted with this control.
It also prevents abnormal high-pressure simultaneously.
The capacity is controlled in the following diagram.
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