Haier AW07LC2VHA Technical Overview page 17

Compressor
The compressor is a variable speed dual rotary type com-
pressor. The compressor has a built in accumulator to protect
against liquid floodback during running operation. A factory
supplied crankcase heater will protect the compressor from
off cycle liquid migration. Additionally, there is an oil separator
located in the outdoor unit that will aid in the return of com-
pressor oil during both cooling and heating modes of opera-
tion.
The normal operating frequency of the compressor is be-
tween 20-95 RPS.
The operation of the compressor is monitored by the ECU for
starting operation, suction line temperature and discharge
line temperature. Should an abnormal condition be detected,
the ECU will in some instances adjust the operational fre-
quency of the compressor or may shut down system opera-
tion and display an appropriate Error Code.
EEV Valves
The metering devices used in the outdoor unit are EEV type
valves. The valve positions are controlled by electronic pulses
received from the ECU. These valves have potentially 500
steps. Each indoor unit has an EEV for cooling mode opera-
tion. The outdoor unit has 1 EEV that is used for heating mode
operation.
OUTDOOR UNIT TECHNICAL OVERVIEW
Outdoor Unit Components
TECHNICAL OVERVIEW
When a call for cooling or heating occurs, the EEV will be po-
sitioned to a starting position. The starting position is based
upon the Outdoor Ambient Air Temperature. For example,
in cooling mode, at outdoor air temperature above 68°F, the
starting position of the valve will be 250 pulses. If the Outdoor
Air Temperature is lower than 68°F, the valve will be opened to
a position equal to 210 pulses.
The actual starting position of the valve is not something a
service technician can use to aid in solving a diagnostic prob-
lem. It is however, good to understand how these systems
fundamentally work.
When the compressor starts and the cooling or heating cycle
starts, the position of the EEV will be adjusted based upon the
Liquid and Gas Temperature Sensors that are associated with
each EEV. The EEV open position will be adjusted to try and
maintain around 10F of suction vapor superheat.
The ECU may also make an open or close adjustment to the
EEV based upon the temperature of the compressor hot gas
discharge line. If the line becomes too hot, or cool, the posi-
tion of the EEV may be altered to ensure the compressor is
not damaged by a lack of refrigerant flow or liquid floodback.
Crankcase Heater
The system has an option for a compressor crankcase heater.
The heater is powered by line voltage via a connection plug on
the ECU. The purpose of the heater is to keep the compressor
oil warm during off cycle periods. Warming the compressor
oil prevents liquid refrigerant from migrating into the com-
pressor shell and mixing with the oil during periods where the
compressor is off.
The heater is energized during off cycle periods when the out-
door air temperature is below 90°F. During running operation,
the heater will be off.
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