Defrost; Automatic Heating Temperature Compensation; Indoor Unit; Temperature Sensors - Haier HSU09VHG(DB)-W Service Manual

ambient and tube, provide information to the outdoor control
board to monitor the system and regulate the frequency of
the compressor, EEV positioning, and outdoor fan speed to
achieve the desired room temperature.
When heating has been satisfied, the outdoor unit compres-
sor will turn off first and followed by the outdoor fan. The
4-way valve will de-energize 2 minutes after compressor
stops.
The indoor unit fan will continue to run at minimum speed un-
til indoor coil temperature reaches a minimum temperature
and it will turn off.
If the system detects a malfunction, it may shut down or
show an error code on the indoor unit display board and/or
outdoor unit main board LED.

Defrost

When the system initiates a call for defrost, the indoor fan
motor stops. The indoor unit display will not change. Any
indoor unit malfunctions will be ignored at this time. The sys-
tem will cycle through the defrost operation. Any indoor unit
malfunctions will be ignored until the compressor restarts
and has been operating for 30 seconds. At the conclusion of
the defrost cycle, the indoor fan will enter the cold air proof
operation. Heat mode resumes.

Automatic Heating Temperature Compensation

When the system enters heating mode, a temperature com-
pensation adjustment is added to the operating parameter.
This adjustment is canceled when exiting heat mode.

Indoor unit

To enter the heat mode, point the infrared remote controller
at the indoor unit and press the power button, then press the
HEAT mode button if not already set to heat mode.
The signals received by the infrared receiver are relayed to
the main board of the indoor unit to turn the system on and
set it to heat mode.
The indoor unit main board will activate the display of the
indoor unit, illuminating the display, indicating the room tem-
perature and current status of the unit.
The indoor unit main board will signal the louver stepper mo-
tor to open the louver to a stationary position.
The indoor unit main board will power up the indoor fan motor
after the outdoor unit has started and heating of the indoor
coil has taken place (see cold air proof operation). The indoor
fan motor has a feedback circuit which provides the indoor
unit main board with information for controlling the speed of
the fan motor.
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Temperature sensors

The indoor unit has two sensors that provide temperature
information to the indoor unit main board. The sensors: an
indoor ambient temperature sensor, and pipe temperature
sensor, are used for controlling the system during heat mode.
The resistance values of the sensors will vary with tempera-
ture. The resistance to temperature values can be found
using a temperature / resistance chart specific to the sensor
being checked.

Communication

The indoor and outdoor unit main boards communicate via a
digital signal on the wire connected to terminal 3 of each unit.
A splice or break in this wire will cause a communication error.
When a command is received from the remote control, the
indoor unit main board communicates with the outdoor unit
main board via the terminal 3 wire to perform the requested
function.

Outdoor unit

Upon a request for heat, the outdoor unit main board applies
power to the 4-way valve, outdoor fan motor and compres-
sor. Depending on system cycling, there may be up to a 3
minute wait period before the compressor and outdoor fan
start.)
NOTE: Do not measure compressor voltages, damage to the
meter may result.
If the ambient room temperature is above the set tempera-
ture, yet lower than 2°F above the set temperature, the
system will adjust the running frequency of the compressor
automatically according to changes in ambient temperature.
The outdoor unit main board also controls the position of the
EEV (Electronic Expansion Valve)
to regulate the flow of refrigerant to the indoor unit evapora-
tor coil.
Temperature sensors
Four temperature sensors located in the outdoor unit provide
temperature information to the outdoor unit main board for
control of the system during heat mode.
The outdoor ambient temperature sensor provides the
temperature of the air drawn into the condenser coil of the
outdoor unit.
The defrost temperature sensor provides the temperature
sensed at the output of the condenser coil.
The suction line temperature sensor provides the tempera-
ture sensed at the incoming suction line pipe.
SEQUENCE OF OPERATION