Low Pressure Check - Daikin VRV RXYMQ-A Series Service Manual

Check
6.2

Low Pressure Check

CHECK 2 Referring to the Fault Tree Analysis (FTA) shown below, probe the defective points
[In cooling]
Defective
low pressure
control
[In both cooling
and heating]
Abnormal drop in
( 2)
low pressure
[In cooling]
(Low evaporating
If the indoor unit
temperature)
electronic
expansion valve is
throttled too much:
( 3)
Defective electronic
expansion valve
control
[In heating]
If the outdoor unit
electronic
expansion valve
excessively
throttled:
( 4)
[In cooling]
Low suction air
temperature of
the evaporator
[In heating]
Less
circulation
quantity of
refrigerant
Degradation
in evaporating
capacity
Note(s)
1. For details of compressor capacity control while in cooling refer to Compressor
2. The "low pressure protection control" includes low pressure protection control and
3. In cooling, the indoor unit electronic expansion valve is used for "superheating
4. In heating, the outdoor unit electronic expansion valve is used for "superheating
Reference
CHECK 7 Refer to page 279.
Reference
CHECK 8 Refer to page 280.
272
Defective low pressure
( 1)
Defective sensor
compressor
Defective main PCB
capacity
control
Defective low pressure
sensor
Defective
low pressure
Defective hot gas EV
protection
control
Defective main PCB
Defective indoor
unit electronic
Defective valve coil
expansion valve
Defective valve body
Defective gas pipe
thermistor of indoor unit
Defective
control
Defective liquid pipe
thermistor of indoor unit
Defective main PCB
Defective outdoor Defective valve coil
unit electronic
expansion valve
Defective valve body
Defective low pressure
sensor
Defective
Defective suction pipe
thermistor
control
Defective main PCB
Low suction air
Short circuit
temperature of
Low room temperature
indoor unit
Defective suction air thermistor of indoor unit
Low suction air temperature of outdoor unit
Defective outdoor air temperature thermistor of outdoor unit
Abnormal piping length
High pipe
Bent or crashed pipe
resistance
Clogging of foreign materials
Stop valve closed
Refrigerant shortage
Moisture choke
Dirty evaporator
Decreased
fan output
Decreased
airflow rate
High
airflow
passage
resistance
Capacity Control on page 56.
hot gas bypass control.
degree control".
degree control of outdoor heat exchanger".
mIs the pressure value checked with the Service Checker
corresponding to the measurement value of the pressure sensor?
mAre the voltage characteristics normal?
mIs the pressure value checked with the Service Checker corresponding
to the measurement value of the pressure sensor?
Defective valve coil
Defective valve body
mAre the voltage characteristics normal?
mAre the coil resistance and insulation normal?
mCheck for the thermistor resistance and connection.
mCheck for the thermistor resistance and connection.
mAre the voltage characteristics normal?
mAre the coil resistance and insulation normal?
mIs the pressure value checked with the Service Checker corresponding
to the measurement value of the pressure sensor?
mCheck for the thermistor resistance and connection.
mIs the suction air temperature less than 14°C?
mIs the room temperature less than 14°C?
mIs the connector properly connected?
Are the thermistor resistance characteristics normal?
mIs the outdoor air temperature less than –20°C?
mIs the connector properly connected?
Are the thermistor resistance characteristics normal?
mDoes the piping length fall in the permissible range?
mConduct visual checks for pipe conditions.
mIs there any temperature difference caused before and after the filter or
branch pipe?
mCheck to be sure the stop valve is open.
mRefer to CHECK 7.
mEliminate moisture by vacuum operation. (Refer to CHECK 8.)
mIs the heat exchanger clogged?
mCan the fan motor be rotated with hands?
Defective fan motor
Are the motor coil resistance and insulation normal?
mIf a spare PCB is mounted, is the
Defective main PCB
(Including capacity setting) capacity setting properly made?
mIs the air filter clogged?
Dirty filter
mIs there any obstacle in the airflow passage?
Obstacle
SiME332106E
mAre the coil resistance and insulation normal?
Part 6 Service Diagnosis