Heating Mode Sequence Of Operation - Haier 2U18MS2VHB Service Manual

Ductless multi-split heat pump, outdoor/indoor, wall mount - highwall, 2'x2' compact cassette, 3'x3' large cassette, slim duct, mid-static ducted, medium static ducted, console
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Heating Mode Sequence of Operation

4-way valve coil:
Refrigerant flow in cooling
OFF
ON
Refrigerant flow in heating
2
Indoor
heat
exchanger
temp.
sensor
FAN-IN
Indoor
ambient
temp.
sensor
Indoor unit A
Indoor unit B
Indoor unit C
Indoor unit D
On a call for heating, the indoor unit will send the room temperature and set-point requirement to the outdoor unit ECU via the
data signal wire path. The data travels from the indoor unit to the outdoor unit via the wire located on terminal 3. The indoor
unit's louver will open the indoor fan will remain off.
EEV valves serving indoor circuits will step to a FULL OPEN BYPASS position. Outdoor EEV valve serving outdoor coil will step
open to a pre-set metering position based upon the temperature of the outdoor air.
The outdoor unit 4 way valve will be energized. Equalization noise will be heard.
The outdoor fan motor will start.
The compressor will start in low RPS speed and gradually speed up.
Indoor fan will begin to operate at slow speed and gradually increase speed.
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 Display.
When the compressor starts, the compressor will discharge hot gas into the oil separator. Oil will be trapped in the separator and
returned to the suction inlet of the compressor via the capillary tube assembly low pressure path.
B-10
2
Unit A gas pipe temp. sensor
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
Unit B liquid pipe temp. sensor
Strainer
Unit C liquid pipe temp. sensor
Strainer
Unit D liquid pipe temp. sensor
Strainer
OUTDOOR TECHNICAL OVERVIEW
Operations
Comp-
ressor
Oil
separator
High pressure
switch
Gas stop valve
5/8
Liquid stop vavle
valve
EEV C
3/8
EEV D
6
Low pressure
Suction temp.
switch
sensor
Discharge temp.
sensor
1
Accumulator
Capillary tube
Pipe sensor
4-way valve
Toci
Outdoor
heat
exchanger
temp.
sensor
EEV O
Strainer
Receiver
Check valve
5
FAN-OUT
Outdoor
ambient
temp.
sensor
Defrost
sensor
4
Distributor

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