SiBE811001EB
Troubleshooting
CONVENI-PACK
286
Check for Causes of Dropping Low Pressure (Air conditioning)
Referring to the Fault Tree Analysis (FTA) shown below, probe the defective points.
CHECK 2-1
Defective valve coil
Defective valve body
Defective suction air thermistor of indoor unit
Low suction air temperature of outdoor unit
Inadequate refrigerant quantity
Moisture choke
Dirty evaporator
Clogging of foreign particles
Stop valve closed
Bent or crashed pipe
Abnormal piping length
Defective control PCB
Defective control PCB
Defective control PCB
Defective low pressure sensor
Defective suction pipe thermistor
Defective control PCB
Short circuit
Low outdoor air temperature
Defective low pressure sensor
Defective low pressure sensor
[In cooling]
[In heating]
Abnormally low
low-pressure
(Low evaporating
temperature)
[In both cooling
and heating]
(See
∗
2.)
[In cooling]
If the indoor unit
electronic expansion
valve is excessively
throttled:
(See
∗
3.)
Defective
low pressure
control
Defective
electronic
expansion
valve
control
Low suction
air
temperature
of the
evaporator
Less
circulation
quantity of
refrigerant
Degradation
in condensing
capacity
Defective
compressor
capacity
control
Defective
low pressure
protection
control
Defective
control
Defective
control
←
Are the electrical characteristics
normal?
←
Are the coil resistance and
insulation normal?
←
Check for the thermistor
resistance and connection.
←
Are the coil resistance and
insulation normal?
←
Are the electrical characteristics
normal?
←
Is the suction air temperature not
less than 14˚C
←
Is the indoor temperature not
more than 14˚C
←
Is the outdoor air temperature
more than -20˚C
←
Eliminate moisture by vacuum operation.
←
Is the heat exchanger clogged?
←
Does the piping length fall in the
permissible range?
←
Conduct visual checks for pipe
conditions.
←
Check to be sure the stop valve is
open.
←
Is there any temperature
difference caused before and
after the filter or branch pipe?
←
Check for the thermistor
resistance and connection.
←
Check for the thermistor
resistance and connection.
←
Are the electrical characteristics
normal?
←
Is the pressure value checked
with the Service Checker
corresponding to the
measurement of the pressure
sensor?
←
Is the pressure value checked
with the Service Checker
corresponding to the
measurement of the pressure
sensor?
←
Is the connector properly
connected?
Are the thermistor resistance
characteristics normal?
←
Is the connector properly
connected?
Are the thermistor resistance
characteristics normal?
←
Is the pressure value checked
with the Service Checker
corresponding to the
measurement of the pressure
sensor?
Defective
indoor unit
electronic
expansion valve
Defective
outdoor unit
electronic
expansion valve
Low suction air
temperature of
indoor unit
High pipe
resistance
Defective valve coil
Defective valve body
Defective gas pipe
thermistor of indoor unit
Defective liquid pipe
thermistor of indoor unit
Defective outdoor air temperature
thermistor of outdoor unit
[In heating]
If the outdoor
unit electronic
expansion valve
excessively
throttled:
(See
∗
4.)
[In cooling]
(See
∗
1.)
∗
1: For details of the compressor capacity control while in cooling, refer to “Compressor PI Control”.
∗
2: The “low pressure protection control” is used low pressure droop control.
∗
3: In cooling, the indoor unit electronic expansion valve is used for “superheated degree control”.
∗
4: In heating, the outdoor unit electronic expansion valve (Y1E) is used for “superheated degree control of outdoor unit heat
exchanger”.