Daikin SkyAir Service Manual page 248

SiBE28-804
<Diagnosis of inadequate refrigerant>
In heating operation
(1) As suction superheat degree increases due to gas shortage, the electronic expansion valve
(2) As suction superheat degree increases due to gas shortage, compressor frequency
(3) Because of (1) and (2) above, evaporator capacity and compressor frequency decrease
(4) If gas shortage worsens, high pressure becomes smaller than saturated pressure equivalent
Heating
High pressure
(Pressure sensor)
Low pressure
(Middle of heat exchanger Tm)
Suction superheat degree
Compressor frequency
Electronic expansion valve
Adequate level
Troubleshooting
tends to open (opens fully) to avoid overheat operation.
decreases because suction superheat degree is controlled in order to prevent oil to the
outdoor heat exchanger from being retained.
despite a large difference (large load) between temperature set by the remote controller and
indoor suction temperature, resulting that high pressure cannot be maintained and heating
capacity becomes unavailable. Also a decrease in evaporator capacity frequently puts the
system in defrost operation.
to indoor heat exchanger temperature (or indoor suction temperature).
(Maintains a certain
level of high pressure)
Indoor heat exchanger temperature (Th2)
Indoor suction temperature (Th1)
Suction superheat degree increases.
In response to decreased evaporator capacity
caused by gas shortage, capacity is controlled in
the inverter in order to maintain high pressure,
which resulting in a rise in frequency.
Troubleshooting by Remote Controller Display / LED Display
Gas shortage warning
As compressor frequency
decreases, high pressure
decreases.
A decrease in evaporator capacity frequently
puts the system in defrost operation.
When frequency drops to the
lowest, a decrease in low
pressure becomes larger.
Drooping control by suction superheat degree
(Prevention of oil to heat exchanger from
being retained)
Electronic expansion valve control by avoiding superheat operation
(Degree of inadequate refrigerant)
Abnormal gas shortage
Reaches the lowest frequency
The maximum opening degree of the
electronic expansion valve (480 pulses)
Inadequate
237