27
2. Outdoor
fan control
(continued)
2. Heating fan control
1) Outdoor fan speed (mode) is controlled on the basis of measurements provided by
the TE temperature sensor.
2) If TE > 25 °C is continuously detected for 5 minutes, the operation may stop.
3) For a specified period after air conditioner startup and during defrosting, this
control is disabled.
4) When refrigerant is in extremely short supply, this control may cause the air
conditioner to be repeatedly turned on and off.
The fan speed
corresponding to the highest
mode varies with the HP
capacity of the outdoor unit.
3. Capacity
control
The compressor is controlled on the basis of capacity demand issued by indoor
controllers.
4.
Refrigerant /
Oil recovery
control
1. During cooling operation, this function is executed to regularly to recover the
refrigerant / oil from the indoor units and connecting pipe-work back to the outdoor
unit. This function is also performed to prevent stagnated refrigerant accumulating in
the outdoor heat exchanger during low ambient cooling.
1) Control conditions
Cooling oil recovery operation is executed approximately every 3 hours.
2) Contents of control
The recovery period lasts for approximately 2 or 3 minutes though this is dependent
on the system capacity.
2. Refrigerant recovery control in heating room
This function is executed regularly to recover the liquid refrigerant from the indoor
unit. It is also used to recover oil present in the outdoor heat exchanger during the
heating overload operation (except during defrost operation).
1) Heating operation oil, recovery control is executed approximately every 4 hours.
2) The period of recovery lasts for approximately 2 to 10 minutes though this is
dependent upon the load condition.
5. Defrosting
control
(reverse
defrosting
method)
1. Defrosting commencement conditions
During heating operation, the cumulative duration of operation in which TE sensor
temperature falls below frost formation temperature is measured, and when this
reaches 55 minutes, defrosting control is introduced. (Just after startup or upon
changeover from cooling to heating, the target cumulative duration is 25 minutes.)
Frost formation temperature
is -0.2 °C.
2. Details of defrosting control
1) The compressor currently in operation is operated at the standby operation speed.
2) When a specified amount of time passes from the time the compressor reached
the standby operation speed, the outdoor fans are turned off by closing the 4-way
valves.
3) The compressor operates at the target rotational speed for defrosting control.
To protect the refrigerating
cycle circuit, the fan mode
may be controlled during
defrosting.
3. Defrosting termination conditions
Defrosting termination conditions are met when the TE temperature sensor
measurement reaches a specified value (roughly 12 °C) a certain period of time
after the commencement of defrosting control. In that event, defrosting termination
control takes over.
During defrosting control,
compressor is controlled
so that its speed does not
exceed 66.0 rps.
4. Details of defrosting termination control
1) Compressor is operated at the standby operation speed.
2) When a specified amount of time passes, the 4-way valve is opened.
3) Indoor heating refrigerant recovery control is performed.
For control details, see “ 4. Refrigerant / Oil recovery control”.
Item
Description of operation, numerical data, and other information
Remarks
Zone A: Lowest mode, timer count for forced compressor shutdown
Zone B: -2/20 seconds (down to lowest mode)
Zone C: -1/20 seconds (down to lowest mode)
Zone D: Hold (staying at current mode)
Zone E: +1/20 seconds (up to highest mode)
Zone F: Highest mode
TE temperature
(°C)
31
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