Panasonic U-10MF1E8 Service Manual page 20

4. Special Controls
4-3-6. Outdoor unit cycle defrost
Outdoor unit cycle defrost is performed in systems where 2 or more outdoor units are connected to the refrigerant
system.
(1) Description of outdoor unit cycle defrost
With this defrost method, when 1 outdoor unit operates in defrost mode (heat exchanger operating as a
condenser), another outdoor unit operates as an evaporator in the same way as in ordinary heating mode. In
this way, the other outdoor unit is heating the unit where defrost is occurring. When 1 outdoor unit completes
defrost, the other outdoor unit performs defrost in the same way. Because the amount of time that the unit
1
operates as an evaporator is very short, there is little danger of frost forming again quickly. Rather, because the
heat source is very powerful, it is possible to shorten the defrost operating time.
(2) Defrost sequence
Outdoor unit cycle defrost is always completed in 2 defrost operations.
(A) When there are 2 outdoor units
(B) When there are 3 outdoor units
Defrost
outdoor unit
Defrost flow E: Evaporator operation
C: Condenser operation
S: Shut off
E C: Switching from evaporator operation to condenser operation
C E: Switching from condenser operation to evaporator operation
Outdoor unit(s) where defrost occurs first
Outdoor unit(s) where defrost occurs secondly
Compressor
Remote
Mode
Controller
Stop
Fan
Cooling
Heating
Auto
Auto. Cooling
Auto. Heating
Time
* Type E1 performs "E
3 minutes.
*1: Function when a common use solenoid valve kit is used and there are more than one (1) indoor unit in the
cooling mode within the same solenoid valve kit.
*2: Function when a common use solenoid valve kit is used and there are more than one (1) indoor unit in the
heating mode within the same solenoid valve kit.
Defrost Evaporator
outdoor unit outdoor unit
First operation
Evaporator Evaporator
outdoor unit outdoor unit
First operation
Defrost
preparation
E
E
Operating Operating
S
*1
(Cooling) S
*2
(Heating) C
S
*1
(Cooling)
S
*2
(Heating)
C
Thermostat ON E
Thermostat OFF S
Thermostat ON C
Thermostat OFF C
Thermostat ON E
Thermostat OFF S
Thermostat ON C
Thermostat OFF
C
1 min
C" for 3 minutes after defrost ends. Therefore, the thermostat remains OFF for
Switch
Evaporator
outdoor unit
Second operation
Switch
Evaporator
outdoor unit
Second operation
Defrost in
progress
1st outdoor unit
:Defrost in progress
C C
E
Stopped
S
S
C
Defrost
S
end
S
judgment
C
E
S
C
C
E
S
C
C
Max. 7 min
1 - 14
3-WAY SYSTEM
Control Functions
Defrost
outdoor unit
Defrost Defrost
outdoor unit outdoor unit
Defrost in
Switch
progress
2nd outdoor unit
:Defrost in progress
C E E
E C C
Operating
S S
S S
C C
Defrost
S S
end
S S
judgment
C C
E E
S S
C C
C C
E E
S S
C C
C C
Max. 7 min
1 min
Defrost end
E or S
C E or S
Stopped
S
S
C
S
S
C
E
S
C
C
E
S
C
C
1 min