Mitsubishi SRK20ZSX-W Technical Manual page 149

Temperature
-20
0
20
40
60
65
1-3) Combustion Charactaristic
R32 is possible to combust slightly when following conditions (gas density and ignition energy) coincide.
a) Combustible gas density by mixture with the air
In the event that if the ignition source which is possible to ignite is within the gas density mentioned in table 3, R32
might combust.
However, the combustible gas density of R32 is higher than that of propane's one.
In addition, since the combustible gas density condition of R32 is possible to cause hypoxia (density of oxygen in the
air is less than 18%), this is not the environment where people can work normally.
Density upper limit (vol%)
Density lower limit (vol%)
b) Energy necessary for ignition.
It is said that R32 is less combustible gas than propane, since the energy which enables to combust is big, for example,
static electricity around the human body and electric lighter (few mJ) can not make it ignite.
Minimum energy to ignite (mJ)
c) Combustion speed
Since the combustion speed of R32 is low, it never combusts explosively like propane.
Combustion speed (cm/s)
Consequently, although the ignition never happens under the conditions of usual use and work, however, in the event of
the ignition, please handle with great care because the fire might extend once the ignition occurs.
1-4) Refrigerant oil for R32
The refrigerant oil for R32 differs from the mineral oil which is being used for R22, since it is based on the synthetic oil for
R32, please ensure to use the designated one.
Comparison of saturated vapour pressure
Refrigerant
R32
0.30
0.71
1.37
2.38
3.84
4.29
Combustible density range
Minimum energy to ignite
Combustion speed
147
-
R410A
0.30
0.70
1.35
2.32
3.73
4.17
R32
29.3
13.3
R32
15
R32
6.7
-
'18 • SRK-T-234
R22
0.14
0.40
0.81
1.43
2.33
2.60
Propane (Reference)
9.5
1.8
Propane
0.246
Propane
38.7