Panasonic U-8ME1E8E Service Manual page 37

9. Defrost Control
9-7. Outdoor unit cycle defrost
Outdoor unit cycle defrost is performed in systems where 2 or more outdoor units are connected to the
refrigerant system.
9-7-1. Description of outdoor unit cycle defrost
In this defrosting, the outdoor units are devided into two groups. When outdoor units in the first defrosting
group operate in defrost mode (heat exchanger operating as a condenser), outdoor units in the second
defronting group operates as an evaporator in the same way as in ordinary heating mode. In this way, outdoor
1
units in the second defronting group supply heat to the unit where defrost is occurring. When outdoor units in
the first defrosting group completes defrost, the other outdoor unit performs defrost in the same way.
9-7-2. Defrost sequence
Outdoor unit cycle defrost is always completed in 2 defrost operations.
- When there are 2 outdoor units
- When there are 3 outdoor units
Defrost
outdoor unit
• Defrost flow E: Evaporator operation
C: Condenser operation
S: Shut off
E
C
Outdoor unit(s) where defrost occurs first
Outdoor compressor(s) where defrost occurs first
Outdoor unit(s) where defrost follows later
Outdoor compressor(s) where defrost follows later
Stopped indoor unit(s)
Indoor units where fan is operating
Heating mode indoor
units
Defrost Evaporator
outdoor unit outdoor unit
First operation
Evaporator Evaporator
outdoor unit outdoor unit
First operation
C: Switching from evaporator operation to condenser operation
E: Switching from condenser operation to evaporator operation
preparation
Thermostat ON
Thermostat OFF
Time
Switch
Evaporator
outdoor unit
Second operation
Switch
Evaporator
outdoor unit
Defrost in
Defrost
progress
C
E C
OFF ON
E E
Defrost
O N
ON
end
S
S
judgment
S
S
C
C
C C
1 min
1 min 5 min
1 - 30
2WAY SYSTEM
Control Functions - Outdoor Unit
Defrost
outdoor unit
Defrost Defrost
outdoor unit outdoor unit
Second operation
Defrost in
Switch
progress
preparation
C E
E
OFF ON
E C C
Defrost
OFF O N
end
S S
judgment
S S
C C
C C
1 min 1 min 5 min
Defrost
E or S
OFF
C E or S
OFF
S
S
C
C
1 min