Daikin FAQ71CVEB Service Manual

Troubleshooting by Remote Controller ESIE15-13B
196 Service Diagnosis
<Diagnosis of inadequate refrigerant>
In heating operation
(1) As suction superheat degree increases due to refrigerant shortage, the electronic expansion valve tends
to open (opens fully) to avoid overheat operation.
(2) As suction superheat degree increases due to refrigerant shortage, compressor frequency decreases
because suction superheat degree is controlled in order to prevent oil to the outdoor heat exchanger from
being retained.
(3) Because of (1) and (2) above, evaporator capacity and compressor frequency decrease 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.
(4) If refrigerant shortage worsens, high pressure becomes smaller than saturated pressure equivalent to
indoor heat exchanger temperature (or indoor suction temperature).
*3 This measured temperature is used to calculate the equivalent saturation pressure of the
refrigerant.
(Refer to P.200.)
Heating
*1
High Pressure
Pressure sensor
*2
Low Pressure
Intermediate heat
exchanger
thermistor (*3)
Heating
(Maintains a certain
level of high pressure)
Electronic expansion valve control
by avoiding superheat operation
In response to decreased evaporator capacity
caused by refrigerant shortage, capacity is
controlled in the inverter in order to maintain high
pressure, which resulting in a rise in frequency.
Drooping control by suction superheat degree
(Prevention of oil to heat exchanger from being
retained)
Suction superheat degree increases.
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.
Suction superheat degree
Compressor frequency
Electronic expansion valve
Adequate level Inadequate
(Degree of inadequate refrigerant)
Refrigerant shortage warning
As compressor frequency
decreases, high pressure decreases.
Abnormal refrigerant shortage
Reaches the lowest frequency
The maximum opening degree of the
electronic expansion valve (480 pulses)
High pressure
(∗1)
Low pressure
(∗2)
Indoor heat exchanger
temperature (Th2)
Indoor suction
temperature (Th1)

Daikin FAQ71CVEB Specifications

General

Brand	Daikin
Model	FAQ71CVEB
Category	Air Conditioner
Language	English