Panasonic U-8MF2E8 Service Manual page 43

9. Defrost Control
9-5. Outdoor Unit Cycle Defrost
Outdoor unit cycle defrost is performed in systems where 2 or more outdoor units are connected to the refrigerant
system.
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 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 defrost operating time.
9-5-1. Start of Outdoor Unit Cycle Defrost
When 1 or more connected outdoor units are satisfied with the conditions of section "9-2" and "9-3" contents,
defrost control is started.
Outdoor unit cycle defrost is performed in all connected outdoor units.
9-5-2. Simplified Flow of Outdoor Unit Cycle Defrost
Whole process
Outdoor unit cycle defrost shall be performed as the flow mentioned below.
(0) Normal operation
(1) Outdoor unit cycle defrost processing time
(2) Normal operation
Reverse cycle defrost process
Outdoor unit cycle defrost is always completed in 2 defrost operations.
(1) When there are 2 outdoor units
Defrost
outdoor unit
(2) When there are 3 outdoor units
Evaporator
Defrost
outdoor unit
outdoor unit
First operation
Evaporator
outdoor unit
First operation
Evaporator
outdoor unit
Switch
Evaporator
outdoor unit
Second operation
Switch
Evaporator
outdoor unit
Second operation
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3WAY SYSTEM
Control Functions
Defrost
outdoor unit
Defrost Defrost
outdoor unit outdoor unit
1