Daikin VRV II-Q RQYQ8-48PY1B Service Manual page 191

SiBE341027
CHECK 3
Check the Factors of Overheat Operation
Identify the defective points referring to the defective factor analysis (FTA) as follows.
Defective
discharge
pipe
temperature
control
Temperature
increase of
discharge
pipe
Compressor
overheat
[In cooling mode]
If the indoor unit
electronic
expansion valve
is excessively
throttled. ( ∗ 3)
Defective
superheated
degree
control.
[In heading
mode] If the
outside unit
electronic
expansion valve
is excessively
throttled. ( ∗ 4)
Refrigerant
shortage
Large resistance
of piping
∗ 1: Refer to "Low pressure protection control" for hot gas bypass control.
∗ 2: Refer to "Subcooling electronic expansion valve control".
∗ 3: "Superheating temperature control" in cooling mode is conducted by indoor unit electronic expansion valve.
∗ 4: Superheating temperature control in heating mode is conducted by outside unit electronic expansion valve (EVM).
∗ 5: Judgement criteria of superheat operation:
(1) Suction gas superheating temperature: 10 degrees and over. (2) Discharge gas superheating temperature: 45 degrees
and over, except for immediately after starting and drooping control, etc..
(Use the above stated values as a guide. Depending on the other conditions, the unit may be normal despite the values
within the above scope.)
Service Diagnosis
Hot gas circuit clogging
Defective hot
Defective solenoid
gas bypass
valve coil
control
Defective solenoid
( ∗ 1)
valve body
Defective service monitor PCB
Subcooling
electronic
[In cooling mode only]
expansion
valve failure
Defective
subcooling
electronic
expansion valve
Control
failure
control
( ∗ 2)
Four way valve is in the
Defective of
middle position.
four way valve
Leak from hot gas bypass
operation
valve
Superheat due to
shaft damage
Superheat due to
defective compressor
Defective valve coil
Indoor unit
electronic expansion
valve failure
Defective valve body
Defective thermistor for
indoor unit gas pipe
Defective control
Defective thermistor for
indoor unit liquid pipe
Defective service monitor PCB
Defective valve coil
Outside unit
electronic expansion
valve failure
Defective valve body
Defective low pressure
sensor
Defective thermistor for
Defective control
suction pipe
Defective service monitor PCB
Irregular piping length
Bend/collapse
(Including moisture choke)
Stop valve is closed.
Troubleshooting by Remote Controller
← Check if coil resistance and insulation
are normal.
Defective valve coil
← Check if coil resistance and
insulation are normal.
Defective valve
body
Defective low
← Check if the voltage property is
pressure sensor
normal.
Defective subcooling
← Check if the connector is connected properly.
heat exchanger outlet
Check if the thermistor resistance property is
thermistor
normal.
Defective service
← Check if the pressure value given by the
monitor PCB
service checker corresponding to actual
measurement value by the sensor.
← Check if the piping temperature connected
to the four way valve is normal.
← Check if coil resistance and insulation are
normal.
← Check if the connector is connected properly.
Check if the thermistor resistance property is
normal.
← Check if the connector is connected properly.
Check if the thermistor resistance property is
normal.
← Check if coil resistance and insulation are
normal.
← Check if the voltage property is normal.
← Check if the connector is connected properly.
Check if the thermistor resistance property is normal.
← Check if the pressure value given by the
service checker corresponding to actual
measurement value by the sensor.
← Refer to
CHECK 7
← Does the piping length fall in the permissible range?
← Conduct visual checks.
← Remove the moisture by vacuum break. (Refer to
← Check if the stop valve is open.
)
CHECK 8
181