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SiUS28-902_a
Troubleshooting by Indication on the Unified ON/OFF Controller
Troubleshooting
156
Check for causes of rise in high pressure
Referring to the Fault Tree Analysis (FTA) shown below, probe the faulty points.
CHECK 1
Short circ
u
it
Rise in high
press
u
re
Local
press
u
re
rise
High pipe
resistance
Stop
v
al
v
e closed
Bent or crashed pipe
Clogging of foreign
¬
Check to
b
e s
u
re the stop
v
al
v
e is open.
¬
Cond
u
ct
v
is
u
al checks for pipe conditions.
¬
Is there any temperat
u
re difference ca
u
sed
b
efore
and after the filter or
b
ranch pipe?
[In cooling]
If the o
u
tdoor
u
nit electronic
expansion
v
al
v
e is throttled:
(See *1.)
Fa
u
lty o
u
tdoor
u
nit electronic
expansion
v
al
v
e
Fa
u
lty indoor
u
nit electronic
expansion
v
al
v
e
Fa
u
lty
v
al
v
e coil
Fa
u
lty
v
al
v
e
b
ody
¬
Are the coil resistance and ins
u
lation normal?
Fa
u
lty
control
Fa
u
lty high press
u
re sensor
Fa
u
lty control P.C.B.
¬
Are the electrical characteristics normal?
¬
Is the press
u
re
v
al
u
e checked
w
ith the Ser
v
ice Checker
corresponding to the meas
u
rement of the press
u
re sensor?
¬
Are the coil resistance and ins
u
lation
normal?
Fa
u
lty high
press
u
re
Fa
u
lty
v
al
v
e coil
Fa
u
lty
v
al
v
e
b
ody
[In heating]
If the indoor
u
nit electronic
expansion
v
al
v
e excessi
v
ely
throttled:
(See *2.)
Fa
u
lty
control
Fa
u
lty high press
u
re sensor
Fa
u
lty indoor
u
nit
li
qu
id pipe thermistor
Fa
u
lty control P.C.B.
¬
Are the electrical characteristics normal?
¬
In the connector properly connected?
Are the thermistor resistance characteristics normal?
¬
Is the press
u
re
v
al
u
e checked
w
ith the Ser
v
ice
Checker corresponding to the meas
u
rement of the
press
u
re sensor?
[In cooling]
High s
u
ction
air
temperat
u
re
of the
condenser
[In heating]
High s
u
ction air
temperat
u
re
of o
u
tdoor
u
nit
Short circ
u
it
High am
b
ient temperat
u
re
¬
Is the s
u
ction air temperat
u
re not more than
115
°
F?
¬
Is the o
u
tdoor temperat
u
re not more than 115
°
F?
High s
u
ction
air temperat
u
re
High am
b
ient temperat
u
re
¬
Is the s
u
ction air temperat
u
re not more than
8
1
°
F?
¬
Is the indoor temperat
u
re not more than
8
1
°
F?
Fa
u
lty s
u
ction air thermistor of indoor
u
nit
High s
u
ction air temperat
u
re of o
u
tdoor
u
nit
Fa
u
lty o
u
tdoor temperat
u
re thermistor of o
u
tdoor
u
nit
¬
Is the connector properly connected?
Are the thermistor resistance characteristics normal?
¬
Is the o
u
tdoor temperat
u
re not more than 61°F
W
B?
¬
Is the connector properly connected?
Are the thermistor resistance characteristics normal?
Degradation
in condensing
capacity
Dirty condenser
Mixing of non-condensa
b
le gas
¬
Is the heat exchanger clogged? (In cooling)
¬
Is air or else mixed in the refrigerant system?
Decreased
fan airflo
w
rate
Decreased
fan
o
u
tp
u
t
Fa
u
lty fan
motor
¬
Can the fan motor
b
e rotated
w
ith hands?
Are the motor coil resistance and
ins
u
lation normal?
¬
If a spare P.C.B. is mo
u
nted, is the capacity
setting properly made?
Fa
u
lty control
P.C.B.
(Incl
u
ding
capacity setting)
High air
passage
resistance
Dirty filter
¬
Is the air filter clogged?
O
b
stacle
¬
Is there any o
b
stacle in the air passage?
Excessi
v
e refrigerant charging
Improper model selection [In heating]
¬
Refer to P.112.
¬
Is the indoor
u
nit too small compared to
the large-sized o
u
tdoor
u
nit?
*1: In cooling, it is normal if the o
u
tdoor
u
nit electronic expansion
v
al
v
e (E
V
1) is f
u
lly open.
*2: In heating, the indoor
u
nit electronic expansion
v
al
v
e is
u
sed for “s
ub
cooled degree control”.
A temperat
u
re difference in excess of 50
°
F
b
et
w
een the inlet and the o
u
tlet is deemed a
b
normal.
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Page 44: ...Other Control SiUS28 902_a 37 Function...
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