Haier GE 2U18MS2HDA Service Manual page 9

4-way valve coil:
OFF Refrigerant flow in cooling
ON
Refrigerant flow in heating
2
Indoor
heat
exchanger
temp.
sensor
FAN-IN
Indoor
ambient
temperature
sensor
On a call for heating, the indoor unit will send the room temperature and set-point requirement to the outdoor unit PCB via the
data signal wire path. The indoor unit louvers will open. The fan will not start until the coil has warmed sufficiently to avoid cold
drafts.
EEVs serving indoor circuits will step to the standard opening. The outdoor EEV opens to a position based upon the outdoor air
temperature.
The 4-way valve will energize and the outdoor fan will start. The compressor starts at a slow speed and will increase based upon
demand. The indoor fan starts after the indoor coil is warm enough to avoid circulating cool air.
With the compressor operating, refrigerant will begin to flow throughout the refrigeration circuit.
The operating frequency of the compressor will be displayed on the Service Monitor Board.
Heating Mode Sequence of Operation
Indoor unit A
Unit B gas pipe temp. sensor
Indoor unit B
Unit C gas pipe temp. sensor
Indoor unit C
Unit D gas pipe temp. sensor
Indoor unit D
3
Unit A liquid pipe temp. sensor
Strainer
Indoor unit A
Unit B liquid pipe temp. sensor
Strainer
Indoor unit B
Unit C liquid pipe temp. sensor
Strainer
Indoor unit C
Unit D liquid pipe temp. sensor
Strainer
Indoor unit D
SEQUENCE OF OPERATION & OPERATIONAL PARAMETERS
Comp-
ressor
Discharge temp.
sensor
Muffler
2
High pressure
swtich
Gas stop valve
4-way valve
5/8
EEV A
Liquid stop valve
EEV B
3/8
EEV C
EEV D
Low pressure
switch
1 Gas-liquid
separator
5
Outdoor
heat
FAN-OUT
exchanger
temp.
sensor
Outdoor
ambient
temperature
sensor
Defrost
sensor
4
Distributor
EEV O
Strainer
Check valve
PAGE 9