Appendix
SiEN34-705
208
General Information
7.14.17 Malfunction Heating Due to Overcharge of Refrigerant
Applicable
Models
VRV in general
Condition
Inverter compressor only operates at low frequency. Discharge temperature of the indoor units
is 25°C or less and thermistor temperature of the liquid pipe is approx. 30°C when it is
monitored through the service mode of the indoor remote control. The low-pressure at that time
is around 0.2MPa.
Cause
Overcharged refrigerant.
Due to overcharge, refrigerant accumulates in the indoor unit. Under this condition, temperature
of the heat exchanger itself drops though the high-pressure rises. In addition, rise of high-
pressure causes rise of liquid pressure that results in minimum opening of the electronic
expansion valve of outdoor units leading to the wet operation.
(The low-pressure at that time comes to be 0.2MPa due to minimum EV opening.)
Measure
Recovers by correcting the refrigerant to the specified amount.
Point of
Diagnosis
1. Use a manifold gauge to measure the high-pressure side of the outdoor unit and the
pressure of service port of the liquid-side stop valve. Then check that the difference between
the pressure on the high-pressure side and the pressure of the liquid pipe (intermediate
pressure) is approx. 0.2MPa or more.
(Approx. 0.2-MPa differential pressure is required to secure the flow rate at the electronic
expansion valve.)
2. Check whether the subcooling of each indoor unit is normal.
Difference between the saturation temperature being equivalent to the high-pressure and
the thermistor temperature of liquid pipe of each indoor unit is approx. 5 to 8°C
(Liquid pipe temperature is normally approx. 38°C or higher.)
