Mitsubishi Electric MXZ-2F33VF, Service Manual

Page: 10 / 94

10
(2) Cautions for refrigerant piping work
New refrigerant R32 is adopted for replacement inverter series. Although the refrigerant piping work for R32 is same as for
R22, exclusive tools are necessary so as not to mix with different kind of refrigerant. Furthermore as the working pressure
of R32 is 1.6 times higher than that of R22, their sizes of flared sections and flare nuts are different.
Thickness of pipes
Because the working pressure of R32 is higher compared to R22, be sure to use refrigerant piping with thickness shown
below. (Never use pipes of 0.7 mm or below.)
Dimensions of flare cutting and flare nut
The component molecules in HFC refrigerant are smaller compared to conventional refrigerants. In addition to that, R32
is a refrigerant, which has higher risk of leakage because its working pressure is higher than that of other refrigerants.
Therefore, to enhance airtightness and strength, flare cutting dimension of copper pipe for R32 has been specified sepa-
rately from the dimensions for other refrigerants as shown below. The dimension B of flare nut for R32 also has partly
been changed to increase strength as shown below. Set copper pipe correctly referring to copper pipe flaring dimensions
for R32 below. For 1/2 and 5/8 inch pipes, the dimension B changes.
Use torque wrench corresponding to each dimension.
Tools for R32 (The following table shows whether conventional tools can be used or not.)
1/4
3/8
1/2
5/8
3/4
6.35
9.52
12.70
15.88
19.05
0.8
0.8
0.8
1.0
—
0.8
0.8
0.8
1.0
1.0
Nominal
dimensions(inch)
Diagram below: Piping diameter and thickness
Outside
diameter (mm)
Thickness (mm)
R32/R410a R22
1/4
3/8
1/2
5/8
3/4 6.35
9.52
12.70
15.88
19.05
9.1
13.2
16.6
19.7
—
9.0
13.0
16.2
19.4
23.3
Nominal
dimensions(inch)
Flare cutting dimensions
Outside
diameter(mm) R32/R410a R22
Dimension A ( )
+0
-0.4
(mm)
1/4
3/8
1/2
5/8
3/4
6.35
9.52
12.70
15.88
19.05
17.0
22.0
26.0
29.0 *
—
17.0
22.0
24.0
27.0
36.0
Nominal
dimensions(inch)
Flare nut dimensions
Outside
diameter(mm)
Dimension B
R32/R410a
* 36.0mm for
indoor unit
of RP100,
125 and 140
R22
(mm)
Dimension A
Dimension B
Tools and materials Use R32 tools Can R22 tools be used? Can R407C tools be used? Can R410a tools be used?
Gauge manifold Air purge, refrigerant
charge and operation
check Tool exclusive for R32
Charge hose
Tool exclusive for R32
Gas leak detector Gas leak check Tool for HFC refrigerant
Refrigerant recovery
equipment
Refrigerant recovery Tool exclusive for R32
Refrigerant cylinder Refrigerant charge Tool exclusive for R32
Safety charger Prevent compressor malfunction
when charging refrigerant by
spraying liquid refrigerant
Tool exclusive for R32
Charge valve Prevent gas from blowing out
when detaching charge hose
Tool exclusive for R32
Vacuum pump
Vacuum drying and air
purge
Tools for other refrigerants
can be used if equipped
with adapter for reverse
fl ow check
(Usable if equipped with
adapter for reverse
fl ow)
(Usable if equipped with
adapter for reverse
fl ow)
(Usable if equipped with
adapter for reverse
fl ow)
Flare tool
Flaring work of piping
Tools for other refrigerants
can be used by adjusting
fl aring dimension
(Usable by adjusting
fl aring dimension)
(Usable by adjusting
fl aring dimension)
(Usable by adjusting
fl aring dimension)
Bender
Bend the pipes
Tools for other refrigerants
can be used
Pipe cutter
Cut the pipes
Tools for other refrigerants
can be used
Welder and nitrogen
gas cylinder
Weld the pipes
Tools for other refrigerants
can be used
Refrigerant charging
scale
Refrigerant charge
Tools for other refrigerants
can be used
Vacuum gauge or
thermistor vacuum
gauge and vacuum
valve Check the degree of vacuum.
(Vacuum valve prevents back
fl ow of oil and refrigerant to
thermistor vacuum gauge)
Tools for other refrigerants
can be used
Charging cylinder Refrigerant charge Tool exclusive for R32 –
: Prepare a new tool. (Use the new tool as the tool exclusive for R32.)
: Tools for other refrigerants can be used under certain conditions.
: Tools for other refrigerants can be used.
OBH790