Daikin SkyAir RZQ200 · 250C7Y1B Service Manual page 191

Diagnosis by Remote Controller
Check No. 8 Check for inadequate refrigerant
As criteria for judging whether refrigerant is inadequate or not, refer to the following operating
conditions.
<Diagnosis of inadequate refrigerant>
In cooling operation
(1) As suction superheat degree increases due to gas shortage, the electronic expansion valve
(2) In response to decreased evaporator capacity caused by gas shortage, capacity is
(3) Because of (1) and (2) above, the compressor frequency decreases despite a large
(4) If gas shortage worsens, the electronic expansion valve remains fully open and suction
180
tends to open (opens fully) in order to avoid overheat operation.
controlled in the inverter in order to maintain low pressure, which results in a decrease in
frequency.
difference (large load) between temperature set by the remote controller and indoor suction
temperature, resulting that cooling capacity becomes unavailable.
superheat degree further increases. In addition, because the compressor frequency drops
to the level of the lowest frequency (52 Hz) and the refrigerant flow rate decrease, low
pressure cannot be maintained.
Cooling
High pressure
(Pressure sensor)
Low pressure
(Pressure sensor)
Suction superheat degree
Compressor frequency
Electronic expansion valve
Adequate level
As compressor frequency
decreases, high pressure
decreases.
(Maintains a certain level
of low pressure)
As the electronic expansion valve
opening degree reaches the maximum,
suction superheat degree increases.
In response to decreased evaporator capacity
caused by gas shortage, capacity is controlled in
the inverter in order to maintain a low pressure,
which resulting in a decrease in frequency.
The maximum opening degree of the
electronic expansion valve (480 pulses)
Avoid overheat operation by
changing SH target value
(Degree of inadequate refrigerant)
SiBE26-701
Abnormal gas shortage
Gas shortage warning
Actual high pressure
When the refrigerant flow rate
decrease, it is impossible to
maintain a low pressure.
Reaches the lowest frequency
Inadequate
Troubleshooting