2WAY VRF SYSTEM
Control Functions
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3. Compressor Control
2WAY VRF SYSTEM
Control Functions
3. Compressor Control
The compressor with higher priority order starts according to the priority orders described on previous page.
The compressor with lower priority order stops according to the priority orders described on previous page.
The inverter compressor can operate within the range in the table below.
2. Operating compressors
When the high pressure is over 435psi (3.0MPa), the upper limit frequency is 90Hz.
The frequency range in the table above is subject to change without notice.
*
3. Stopping compressors
(3) Operation When Starting 2 Compressors Mounted in Outdoor Unit
(4) Operating Frequency Range of Inverter Compressor
Once a compressor stops, it will not start for a period of 3 minutes (3-minute forced OFF).
However, this does not apply when the compressor was forced to stop as the result of a special control operation.
(start control, defrost control, refrigerant oil recovery control, etc.)
(5) Forced Stopping of Compressor
(6) Horsepower Control (Roadmap Control)
When necessary capacity gradually increases and one more inverter compressor is additionally started under
the present operating compressor, reduce the compressor frequency to 25Hz temporarily and then start an additional
compressor.
The operation noted above is performed when 1st compressor or 2nd compressor is additionally started.
If necessary capacity is initially higher and two compressors are started simultaneously, the operation noted above
is not performed and both of them are regarded as the target frequency.
Type of outdoor unit
Minimum frequency (Hz)
Maximum frequency (Hz)
80
72
96
120
144
100
15
80
15
15
15
80
If the low pressure is over 213psi (1.47MPa) during operation of the inverter compressor, the system is stopped.
(P27: Pre-trip)
If the high pressure is over 450psi (3.1MPa) and the minimum frequency operation is in progress, the system
is stopped. (P25: Pre-trip)
1
Horsepower control (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.
There are two types of controls; one is the pressure detected by the pressure sensor and the other is detected
by 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
If 2 inverter compressors are simultaneously operating in the same outdoor unit, the frequency of 1st
compressor becomes 5Hz lower than that of the 2nd compressor.
4
3
2
(6) Capacity Control (Roadmap control)
1 The capacity control by the compressors is performed according to the pressure sensor attached to the outdoor
unit and temperature thermistor attached to the indoor / outdoor unit heat exchanger.
* With roadmap control, the pressure detected by the pressure sensor is converted to saturation temperature
before it is used by microcomputer. This converted temperature is called “pressure sensor temperature”.
2 This control is performed every 30 seconds.
3 Required level of each indoor unit
Required level of indoor unit is calculated by difference between preset temperature in remote controller and
intake temperature of indoor unit (TA), difference between preset discharge air temperature in EEPROM on
indoor unit PCB and discharge air temperature of indoor unit (TF).
Required level has “0” to “30” phases. This level becomes “31” at the test run.
The target temperature of indoor unit heat exchanger is decided according to the maximum required level.
* Target temperature of all indoor units heat exchanger is same value because all indoor units are connected
with the same pressure piping.
4 Definition of evaporation temperature and condensation temperature
●
Evaporation temperature (Te):
Shows the lowest temperature among the temperature sensors (E1 or E3) when the indoor unit heat exchanger
is functioning as an evaporator.
●
Condensation temperature (Tc):
Shows the highest temperature among the high-pressure saturated temperature in the system.
6-1. Evaporation temperature adjustment by roadmap control
The cooling capacity is adjusted with this control. It prevents freezing of the indoor unit's heat exchanger and the
dew to the outside panel of the indoor unit. The capacity is adjusted according to the following figure.
* The evaporation temperature area changes depending on the maximum required level of each indoor unit as
shown above.
* Area C is regarded as area B for 6 minutes after compressor starts.
* 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.
* The evaporation temperature is not adjusted while specially controlling defrosting and the oil recovery, etc.
* The evaporation temperature is not adjusted when there are one or more indoor units that select the test run.
If one or more indoor units are selected into test run, the system doesn't stop in all states except alarm appearing.
* The test run will finish automatically in about one hour.
Compressor capacity increase possible
43.0 (6.1)
Compressor capacity
increase prohibited
Compressor capacity decrease
Max. required level
15
0
42.8 (6.0)
37.4 (3.0)
deg
37.2 (2.9)
42.8 (6.0)
37.4 (3.0)
60.8 (16.0)
unit: °F (°C)
55.4 (13.0)
30
51.8 (11.0)
46.4 (8.0)
Area B
Area C
Area A
Evaporation temperature area
SM830237-07_北米向け2WAY_VRF.indb 7
18/06/19 18:55:30
