GREE Air-ccoled Closed Control Unit Service Manual
100
3. Case Study
Case 1
Malfunction Phenomenon
: Low pressure protection occurs after the unit operates
normally in cooling mode for a period of time.
Possible causes:
pressure controller is abnormal; parameter setting of touch screen is
abnormal; air return and supply are not smooth; pipeline is blocked (including expansion valve,
filter, etc.).
Analysis of root cause:
Firstly, check each set parameter and the set parameters are
factory setting so there is no problem. Check if air flow around the air inlet and outlet is smooth
and check if there is any obstruction. After inspection, it is found that there is no obstruction
around the air inlet and outlet and air flow and air volume are normal. Check if wiring of
pressure controller is normal. Check low pressure of the unit and the low pressure is 0.05MPa
which is within the low pressure protection range. So there is no malfunction of pressure
controller. Check the status of pipeline. Observe the pipe by viewing mirror and it is found that
there is almost no liquid flowing through the mirror. The pipeline in front of the mirror may be
blocked. After inspection of pipeline, it is found that the temperature difference between the
front part and the rear part of the filter is huge but other pipes are normal. So we can get a
conclusion that the filter is blocked. After replacing the filter, the unit resumes normal operation.
Conclusion:
There are obstacles in the cooling system, which causes blockage of filter
when the system is running.
Case 2
Malfunction Phenomenon:
high water level protection of humidifier during debugging of
the unit.
Possible causes:
（
1
）
High water level protector has malfunction;
（
2
）
Water discharge valve can’t be started up;
（
3
）
Water inlet valve can’t be turned off;
（
4
）
Current transformer is damaged;
（
5
）
Water quality is bad.
Analysis of root cause:
Firstly, check if water level of humidifier tank is normal. Actually,
the tank is full of water and there is high water level. Therefore, high water level protector
doesn’t have malfunction. Switch the unit to manual debugging mode by touchable screen.
Manually turn off/on the valve of humidifier and it is works normally. So there is no relevant
malfunction. Then manually drain the water inside the tank of humidifier and then manually turn
