Compressor; Eev Valves; Crankcase Heater - 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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Compressor

The compressor is a variable speed dual rotary type
compressor. 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 compressor oil during both cooling and heating modes of
operation.
The normal operating frequency of the compressor is
between 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
frequency of the compressor or may shut down system
operation 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
operation. The outdoor unit has 1 EEV that is used for heating
mode operation.
When a call for cooling or heating occurs, the EEV will be
positioned to a starting position. The starting position is
based upon the Outdoor Ambient Air Temperature. For
B-6
Components
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
problem. 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
position 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
compressor shell and mixing with the oil during periods where
the compressor is off.
The heater is energized during off cycle periods when the
outdoor air temperature is below 90°F. During running
operation, the heater will be off.
OUTDOOR TECHNICAL OVERVIEW

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