Cooling/Heating Mode Switching - Daikin REYQ-XA Service Manual

Special Control
7.5

Cooling/Heating Mode Switching

[While in cooling/heating mixed mode, single-room cooling → heating]
First, the electronic expansion valve of the indoor unit in cooling operation will close, and the Y2E and Y3E electronic
expansion valves of the branch selector unit will all close once.
Next, the Y2E electronic expansion valve will open little by little to perform pressure equalization.
Then the electronic expansion valve will fully open, and the electronic expansion valve of the indoor unit will open to
activate the heating circuit.
The required switching time is approximately 6 minutes. (Field settings, however, can shorten the time from 6 minutes to 4
minutes.)
(1) In cooling operation
(2) In equalization
(3) To heating mode
129
Outdoor unit
Cooling unit
Indoor unit
(close)
Indoor unit
Heating unit
Branch Selector unit
Liquid pipe
Y1E
Dual pressure gas pipe
Y2E
Y3E
Suction gas pipe
Branch Selector unit
Liquid pipe
Y1E
Dual pressure gas pipe
Y2E (open)
Y3E (close)
Suction gas pipe
Branch Selector unit
Liquid pipe
Y1E
Dual pressure gas pipe
Y2E
Y3E
Suction gas pipe
SiUS371901E
Functions and Control