GREE U-Match 6 SERIES UNIT SERVICE MANUAL
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2.2.1.2 EXV Control
When the unit is first started, the electronic expansion valve will reset control. During the process, the
expansion valve will produce rattling sound. When cooling or heating mode is turned on, the valve will be
open at a certain step before the compressor starts.
2.2.1.3 Outdoor Fan Control
This series air conditioner has two types of outdoor units: one with a single fan and the other with
double fans. The outdoor fan can run at the highest level 15 and the lowest level 1. By controlling the
speed of outdoor fan, the unit can achieve cooling at low temperature and heating at high temperature. In
fan mode, outdoor fan will not work.
2.2.1.4 4-way Valve Control
After heating mode is turned on for a while, 4-way valve will be energized to change the direction of
refrigerant flow so that the system can run in heating and the indoor unit will not blow cold air. Under other
modes, the valve will not be energized.
To avoid the 4-way valve from incorrectly changing directions, when the unit stops in heating, due to a
temperature point or other protection reasons, the 4-way valve will continue to function temporarily and
lose power after a while.
There must be adequate differential pressure for the 4-way valve to change directions.
2.2.2 Special Control
2.2.2.1 Defrosting Control
ODU defrosting control in heating: Defrosting will start when the temperature sensed by outdoor tube
temperature sensor reaches a preset value. During defrosting, the 4-way valve will switch to the cooling
condition, and outdoor and indoor fans will both stop. When the temperature sensed by outdoor tube
temperature sensor reaches the preset value of defrosting stop, system will quit defrosting. The 4-way
valve will switch back to the heating condition, outdoor fan will start working first and indoor fan will
resume its previous fan speed after performing cold air prevention.
2.2.2.2 Oil Return Control
If the unit is running at low frequency for a long time, system will enable oil return control. This is to
lead oil in the pipeline back to the compressor so that the compressor will not be lack of oil. Generally, the
oil return takes about 5min. The compressor running frequency will be raised to the preset oil return
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