Toshiba MAR-C104M8-1-PE Service Manual page 51

NO. CONTROL
Simultaneous
4
Cooling / Heating
operation
3-Pipe ONLY
a. Changeover between cooling and heating operations for each indoor unit.
The solenoid valves inside the Multi controller are energised when operation
commands are sent from the Indoor units.
• SVS valve (suction side) opens for a cooling command.
• SVD valve (discharge side) opens for a heating command.
b. Determination of the Outdoor unit operation mode and frequency of the
compressor.
These are determined by the difference between the total requested cooling
command frequencies and the total requested heating command frequencies
of all Indoor units.
c. Outdoor unit refrigerant control during cooling dominant mode.
• Refrigerant flow is controlled by PMV2. The degree of opening is controlled
by the difference of all requested cooling and heating command
frequencies and the compressor operation frequency.
This flow control is required to divide cooling exhaust heat appropriately
between Indoor units in heating mode and the Outdoor unit heat exchanger.
• High pressure control is performed to ensure that the capacity of the
Indoor units in heating is maintained. This is controlled by the Outdoor
unit fan control and the changeover from the main heat exchanger to the
sub heat exchanger.
d. Outdoor unit refrigerant control during heating dominant mode.
• Superheat control is performed by the Outdoor unit expansion valve.
• Evaporating temperature control is performed by the Outdoor unit fan
control to ensure that the capacity of the Indoor units in cooling mode is
maintained.
• Changeover from expansion valve to capillary control is performed
when there is a minimal difference between the cooling and heating
demands and the heat absorption of the Outdoor unit heat exchanger is low.
DESCRIPTION
54