SiAF341904E
Check
Part 6 Service Diagnosis
293
6.6 Refrigerant Shortage Check
CHECK 7
In case of
VRV
systems, the only way to judge as the shortage of refrigerant is with operating
conditions due to the relationship to pressure control and electronic expansion valve control.
As information for making a judgment, refer to the information below.
Diagnosis of refrigerant shortage
1. The superheating degree of suction gas rises. Consequently, the compressor discharge gas
temperature becomes higher.
2. The superheating degree of suction gas rises. Consequently, the electronic expansion valve
turns open.
3. Low pressure drops to cause the unit not to demonstrate cooling capacity.
Cooling
High press
u
re
Lo
w
press
u
re
Fre
qu
ency
The opening degree of the indoor
u
nit
electronic expansion
v
al
v
e
b
ecomes
larger.
Either of the electronic expansion
v
al
v
es
b
ecomes f
u
lly open.
Fre
qu
ency comes to the minim
u
m le
v
el.
Fan control is acti
v
ated for high
press
u
re protection
u
nder
cooling control at lo
w
o
u
tdoor
air temperat
u
re, i.e., the fan is
h
u
nting at high press
u
re.
High press
u
re drops
w
ith decrease in
compressor capacity.
If fre
qu
ency comes to the
minim
u
m le
v
el, lo
w
press
u
re cannot
b
e
maintained.
Lo
w
press
u
re rises as the
opening degree of the indoor
u
nit electronic expansion
v
al
v
e
b
ecomes larger.
Fre
qu
ency slightly increases
u
nder the capacity control.
(Degree of refrigerant shortage)
Higher degree of shortage
Proper amo
u
nt
(Lo
w
press
u
re
is maintained at
a constant
le
v
el.)
To maintain lo
w
press
u
re,
fre
qu
ency drops
d
u
e to the
capacity control.
