Panasonic U-4LE1E5 Service Manual page 16

3. Special Controls
3-2. Reverse Cycle Start Control
Reverse cycle start control is performed under the following conditions:
• The outdoor unit starts in Heating mode after microcomputer initialization when the power was turned ON.
• The outdoor unit starts in Heating mode after it was stopped for 1 hour or longer.
1
When the outdoor unit starts in Heating mode after having been stopped for a long period of time, this control first
operates the unit in Cooling mode to return refrigerant from the outdoor unit heat exchanger to the liquid tubing.
This prevents back-flow of the refrigerant liquid which had accumulated in the outdoor unit heat exchanger.
Control time
Outdoor units
Electronic
control valve
Indoor
units
Fan
3-3. Inter Systems Refrigerant Oil Recovery Control
3-3-1. Inter systems refrigerant oil recovery cycle
In both indoor unit Cooling mode and Heating mode, this control is performed in the cooling cycle after a certain
amount of time has passed.
3-3-2. Start of inter systems refrigerant oil recovery control
This control is performed periodically after the total compressor operating time exceeds 150 minutes.
3-3-3. Flow of inter systems refrigerant oil recovery control
(1) Simplified flow of inter systems refrigerant oil recovery control
Inter systems refrigerant oil recovery control follows this flow process:
Normal
operation
Control time
Outdoor units
Electronic
control valve
Indoor
units
Fan
3-4. Reverse cycle Defrost Control
3-4-1. Defrost control method
Defrost with this system is done by reverse cycle defrost.
3-4-2. Conditions for start of defrost
Defrost control is started when the "frost detection" conditions are met, and the "defrost mask time" has elapsed.
1 minute
Operates at a compressor frequency of 46 Hz.
All indoor units operate at a fixed pulse according to the indoor
unit capacity.
The fan operates at the set fan speed, is stopped, or operates at
"Lo" fan speed, according to the operation mode of the indoor unit.
1-minute Inter systems refrigerant oil
stop recovery control (3-minute)
3 minutes (stops once before and after control)
Operates at a compressor frequency of 65 Hz.
However depending on the operating conditions, the frequency
may be lower than this value.
All indoor units operate at a fixed pulse according to the indoor
unit capacity.
The fan operates at the set fan speed, is stopped, or operates at
"Lo" fan speed, according to the operation mode of the indoor unit.
1-minute
stop
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Mini VRF SYSTEM
Control Functions
Normal
operation