Toshiba MCY-MHP0404HS(J)-E Service Manual page 32

Item Description of operation, numerical data, and other information
2. Outdoor 2. Heating fan control
fan control 1) Outdoor fan speed (mode) is controlled on the basis of measurements provided by
(continued) 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.
TE temperature
(°C)
3. Capacity The compressor is controlled on the basis of capacity demand issued by indoor
control controllers.
4. 1. During cooling operation, this function is executed to regularly to recover the
Refrigerant / refrigerant / oil from the indoor units and connecting pipe-work back to the outdoor
Oil recovery unit. This function is also performed to prevent stagnated refrigerant accumulating in
control 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 1. Defrosting commencement conditions
control During heating operation, the cumulative duration of operation in which TE sensor
(reverse temperature falls below frost formation temperature is measured, and when this
defrosting reaches 55 minutes, defrosting control is introduced. (Just after startup or upon
method) changeover from cooling to heating, the target cumulative duration is 25 minutes.)
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.
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.
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".
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
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Remarks
The fan speed
corresponding to the highest
mode varies with the HP
capacity of the outdoor unit.
Frost formation temperature
is -0.2 °C.
To protect the refrigerating
cycle circuit, the fan mode
may be controlled during
defrosting.
During defrosting control,
compressor is controlled
so that its speed does not
exceed 66.0 rps.