Panasonic U-20ME1E81, Service Manual

Page: 36 / 177

2WAY SYSTEM
Control Functions
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Outdoor Unit
1 - 28
1
9. Defrost Control
9. Defrost Control
9. Defrost Control
2WAY SYSTEM
Control Functions-Outdoor Unit
9-4. Reverse Cycle Defrost
9-4-1. Start of Reverse Cycle Defrost
9-4-2. Simplified Flow of Reverse Cycle Defrost
Reverse cycle defrost is performed in systems where only 1 outdoor unit is connected to the refrigerant system.
When conditions of section “9-2” and “9-3” contents are satisfied, defrost control is started.
Whole process
Reverse cycle defrost shall be performed as the flow mentioned below.
(0) Normal operation
(1) Pre-processing time of reverse cycle defrost for 1 minute
(2) Reverse cycle defrost processing time
(3) Post-processing time of reverse cycle defrost for 1 minute
(4) 4-way valve adjustment control
(5) Normal operation
Reverse cycle defrost process
This reverse cycle defrost process is performed after outdoor units and indoor units are changed to the cooling
cycle.
Outdoor unit operates at maximum horsepower.
Heat exchanger is acting a condenser.
Valves at all indoor units operate at a fixed pulse according to the
indoor unit capacity.
Control time
Outdoor units
Electronic control valve
Minimum 1 minute – Maximum 16 minutes
(Until all outdoor units’ heat exchanger temperature ≥ 15°C)
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 the 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.
Fan
As for heating thermostat ON indoor units, follow the indoor unit
control system.
The fan speed of the heating thermostat OFF high static pressure
ducted type indoor unit (Type E1) is changed to LL.
Fan and/or heating (thermostat OFF) operation of indoor unit will
be stopped.
All Indoor Units
9. Defrost Control
2WAY SYSTEM
Control Functions-Outdoor Unit
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) 4-way valve adjustment control
(3) Normal operation
Outdoor Unit cycle defrost process
Outdoor unit cycle defrost is always completed in 2 defrost operations.
(1) When there are 2 outdoor units
(2) When there are 3 outdoor units
Defrost
outdoor unit
Evaporator
outdoor unit
Defrost
outdoor unit
Evaporator
outdoor unit
Second operation First operation
Switch
Defrost
outdoor unit
Evaporator
outdoor unit
Evaporator
outdoor unit
Defrost
outdoor unit
Evaporator
outdoor unit
Defrost
outdoor unit
Second operation First operation
Switch
SM830204-05_2WAY SYS.indb 28 2015/01/21 17:00:03