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Airtight Test, Evacuation, And Refrigerant Charging; Thermal Insulation Of Refrigerant Piping - Mitsubishi Electric PUH-P200 Installation Manual

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H Flare nut
[Tightening torque: 120 N·m (1200 kg·cm)
Loosen and tighten this nut using a double-ended wrench.
Coat the flare contact surface with refrigerator oil (Ester oil, ether oil or alkylbenzene
[small amount]).]
I ø12.7 PUH-P200, 250
J ø25.4 PUH-P200
ø28.58 PUH-P250
K Field piping
[Braze to the connecting pipe. (When brazing, use unoxidized brazing.)]
L Close-packed packing
M Hollow packing
Appropriate tightening torque by torque wrench:
Copper pipe external dia. (mm)
Tightening angle standard:
Pipe diameter (mm)
Tightening angle (°)
ø6.35, ø9.52
60 to 90
ø12.7, ø15.88
30 to 60
[Fig. 8.2.3] (P.3)
If a torque wrench is not available, use the following method as a standard:
When you tighten the flare nut with a wrench, you will reach a point where
the tightening torque will abrupt increase. Turn the flare nut beyond this point
by the angle shown in the table above.
1. Nitrogen gas pressurization
(1) After pressurizing to the design pressure (3.3 MPa) using nitrogen gas, let stand for about one
day. If the pressure does not drop, airtightness is good.
However, if the pressure drops, since the leaking point is unknown, the following bubble test
may also be performed.
(2) After the pressurization described above, spray the flare connection parts, brazed parts, flanges,
and other parts that may leak with a bubbling agent (Kyuboflex, etc.) and visually check for
(3) After the airtight test, wipe off the bubbling agent.
2. Pressurization using refrigerant gas and nitrogen gas
(1) Pressurizing to a gas pressure of approximately 0.2 MPa, pressurize to the design pressure
(2.94 MPa) using nitrogen gas.
However, do not pressurize at one time. Stop during pressurization and check that the pres-
sure does not drop.
(2) Check for gas leaks by checking the flare connection parts, brazed parts, flanges, and other
parts which may leak using an R407C compatible electric leak detector.
(3) This test may be used together the with bubble type gas leak test.
2 Evacuation
Evacuate with the ball valve of the outdoor unit closed and evacuate both the
connection piping and the indoor unit from the service port provided on the ball
valve of the outdoor unit using a vacuum pump. (Always evacuate from the
service port of both the liquid pipe and the gas pipe.) After the vacuum reaches
5 Torr, continue evacuation for at least one hour or more.
* Never perform air purging using refrigerant.
[Fig. 8.3.2] (P.3)
A System analyzer
B Lo Knob
D Ball valve
E Liquid pipe
G Service port
H Three-way joint
J Valve
K Cylinder
M Vacuum pump
Always add an appropriate amount of refrigerant. Also always seal the
system with liquid refrigerant. Too much or too little refrigerant will cause
Use a gauge manifold, charging hose, and other parts for the refrigerant
indicated on the unit.
Use a graviometer. (One that can measure down to 0.1 kg.)
Use a vacuum pump with a reverse flow check valve.
(Recommended vacuum gauge: ROBINAIR 14830A Thermistor Vacuum
Also use a vacuum gauge that reaches 0.5 Torr or greater after operating
for five minutes.
Tightening torque (N·m) / (kg·cm)
14 to 18 / 140 to 180
35 to 42 / 350 to 420
50 to 57.5 / 500 to 575
75 to 80 / 750 to 800
Airtight test procedure
C Hi Knob
F Gas pipe
I Valve
L Scale
Always remove the connecting pipe from the ball valve and braze it out-
side the unit.
- Brazing the connecting pipe while it is installed will heat the ball valve and
cause trouble or gas leakage. The piping, etc. inside the unit may also be
Use ester oil, ether oil or alkylbenzene (small amount) as the refrigerator
oil to coat flares and flange connections.
- The refrigerator oil will degrade if it is mixed with a large amount of mineral
8.3. Airtight test, evacuation, and refrigerant
1 Airtight test
Perform with the stop valve of the outdoor unit closed, and pressurize the con-
nection piping and the indoor unit from the service port provided on the stop
valve of the outdoor unit. (Always pressurize from both the liquid pipe and the
gas pipe service ports.)
[Fig. 8.3.1] (P.3)
A Nitrogen gas
B To indoor unit
D Lo Knob
E Hi Knob
G Liquid pipe
H Gas pipe
J Service port
<For R407C models>
The method of conducting the airtight test is basically the same as for R22 models.
However, since the restrictions have a large affect on deterioration of the refrigera-
tor oil, always observe them. Also, with nonazeotropic refrigerant (R407C, etc.),
gas leakage causes the composition to change and affects performance. There-
fore, perform the airtightness test cautiously.
Do not use a leak detection additive.
• If a flammable gas or air (oxygen) is used as the pressurization
gas, it may catch fire or explode.
• Do not use a refrigerant other than that indicated on the unit.
• Sealing with gas from a cylinder will cause the composition of
the refrigerant in the cylinder to change.
• Use a pressure gauge, charge box, and other parts especially for
• An electric leak detector for R22 cannot detect leaks of R407C.
• Do not use a haloid torch. (Leaks cannot be detected.)
3 Refrigerant Charging
Since the refrigerant used with the unit is nonazerotropic, it must be charged
in the liquid state. Consequently, when charging the unit with refrigerant from
a cylinder, if the cylinder does not have a syphon pipe, charge the liquid refrig-
erant by turning the cylinder upside-down as shown below. If the cylinder has
a syphon pipe like that shown in the figure at the right, the liquid refrigerant
can be charged with the cylinder standing upright. Therefore, give careful at-
tention to the cylinder specifications. If the unit should be charged with gas
refrigerant, replace all the refrigerant with new refrigerant. Do not use the
refrigerant remaining in the cylinder.
[Fig. 8.3.3] (P.3)

8.4. Thermal insulation of refrigerant piping

Be sure to give insulation work to refrigerant piping by covering liquid pipe and gas
pipe separately with enough thickness heat-resistant polyethylene, so that no gap
is observed in the joint between indoor unit and insulating material, and insulating
materials themselves. When insulation work is insufficient, there is a possibility of
condensation drip, etc. Pay special attention to insulation work to ceiling plenum.
[Fig. 8.4.1] (P.3)
A Steel wire
C Asphaltic oily mastic or asphalt
E Outer covering B
C System analyzer
F Stop valve
I Outdoor unit
B Piping
D Heat insulation material A


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