SiENBE28-901
Description of Functions and Operation
Air Cooled Refrigeration Condensing Unit
55
(7) Oil return control
Recover the refrigeration oil that has been left standing in the system at regular intervals.
Recover the oil into the outdoor unit, using a timer and low pressure.
(8) Four way valve control
To standardize the hardware with the Japanese domestic models, the European models are
also equipped with four-way valves.
The circulation volume has been factory set to insure that the four-way valve switches over
properly. This allows the valve to be initialized to the proper position when the power is turned
on.
ON condition: The valve will be activated when the differential pressure at start-up is 0.294
MPa or less.
OFF condition: The differential pressure stays above 0.49 MPa for 10 seconds, or the
watchdog timer reaches 90 seconds.
(Low, high pressure and discharge gas protection will take priority.)
For 5 and 6 AY1 models, the INV compressor steps will be increased. For the other models, the
STD compressors will be operated.
(9) High pressure protection control
If the following condition is met, the compressor load will be reduced significantly, as shown
in the block diagram below.
After multiple retries are made and the retry counter is reached, the compressor will stop and
declare a problem (abnormal stop). (For details, see the list of errors.)
The high-pressure retry code "E3" and the number of retries will be sent to the AIRNET.
High pressure sensor>3.479 MPa.
If the high pressure switch (operating pressure: 3.8 MPa) is activated (high pressure sensor
reading
≥
3.567 MPa), the compressor will stop and declare a problem (abnormal stop).
To reset, turn off the power switch (or operation switch) and turn it back on again.
Oil return
control
Objective:
Recovers the refrigeration oil from the evaporator by putting the refrigerant into a wet
state by utilizing a delay in response to the mechanical expansion valve. The operation
output will be turned on/off using the actual low pressure.
or
Oil return by turning on/off the
indoor unit solenoid valve
Oil return by increasing the
compressor frequency
Objective:
Increases the compressor speed to provide sufficient refrigerant speed in the suction
pipe. Then the oil left standing in the suction pipe will be recovered into the outdoor unit.
Normal capacity
control
Normal performance
control
• Continuous operation time during oil return
≥
40 minutes
• 90 seconds have passed
• Low pressure (LP)
≥
0.196 MPa
• The circulating volume used for oil return
continues to be less than specified for 60 to 120
minutes or more. (*1)
• The circulating volume used for oil return
continues to be more than specified for 5
minutes
• Oil return has continued for 10 minutes.
or
Recover the oil by increasing
the compressor frequency
Indoor solenoid
valve: ON
Indoor solenoid
valve: OFF
Recovering the oil by turning on/off the indoor solenoid valve
or
or
• HP<3.04MPa
• LP>0.245MPa
• HP<3.04MPa
• LP<0.196MPa
• 30 seconds have passed.
(*1)
Compressor steps
Low load
High load
LP
High
Low
Oil return
interval: Short
Oil return
interval: Long
Operating mode
3, 4
2, 5
1
Stops the STD2
compressor.
Stops the STD1
compressor.
Reduces the INV
compressor by 5 steps.
