Airtight Test, Evacuation, And Refrigerant Charging; Thermal Insulation Of Refrigerant Piping - Mitsubishi Electric PUHY-P-YREM-A Installation Manual

Appropriate tightening torque by torque wrench:
Copper pipe external dia. (mm)
ø6.35
ø9.52
ø12.7
ø15.88
ø19.05
Tightening angle standard:
Pipe diameter (mm) Tightening angle (°)
ø6.35, ø9.52 60 to 90
ø12.7, ø15.88 30 to 60
ø19.05 20 to 35
[Fig. 8.2.4] (P.3)
Note:
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 abruptly increase. Turn the flare nut beyond this
point by the angle shown in the table above.
Caution:
• 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
burned.
1. Nitrogen gas pressurization
(1) After pressurizing to the design pressure (2.94 MPa) using nitrogen gas, allow it to 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
bubbles.
(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 refrigerant piping that is connected to the
indoor unit closed, and evacuate both the connection piping and the indoor
unit from the service port provided on the ball valve of the refrigerant piping
that is connected to the indoor unit using a vacuum pump. (Always evacuate
from the service port of both the high press pipe and the low press pipe.) After
the vacuum reaches 650 Pa [abs], 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
Note:
• Always add an appropriate amount of refrigerant. Also always seal the
system with liquid refrigerant. Too much or too little refrigerant will cause
trouble.
• 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
Gauge)
Also use a vacuum gauge that reaches 0.5 Torr or greater after operating
for five minutes.
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 refriger-
ant 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 attention
Tightening torque (N·m)
14 to 18
35 to 42
50 to 57.5
75 to 80
100 to 140
Airtight test procedure
C Hi Knob
F Gas pipe
I Valve
L Scale
• Use ester oil, ether oil or alkylbenzene (small amount) as the refrigerat-
ing machine oil to coat flares and flange connections.
- The refrigerating machine oil will degrade if it is mixed with a large amount of
mineral oil.
• Do not use a leak detection additive.
8.3. Airtight test, evacuation, and refrigerant
charging
1 Airtight test
Perform with the ball valve of the refrigerant piping that is connected to the
indoor unit closed, and pressurize the connection piping and the indoor unit
from the service port provided on the ball valve of the refrigerant piping that is
connected to the indoor unit. (Always pressurize from both the high press pipe
and the low press 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
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 refriger-
ating machine oil, always observe them. Also, with nonazeotropic refrigerant (R407C,
etc.), gas leakage causes the composition to change and affects performance.
Therefore, perform the airtightness test cautiously.
• 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
R407C.
• An electric leak detector for R22 cannot detect leaks of R407C.
• Do not use a haloid torch. (Leaks cannot be detected.)
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 re-
maining in the cylinder.
[Fig. 8.3.3] (P.3)
<In case of the cylinder having no syphon pipe.>
A Syphon pipe

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.4)
A Steel wire
C Asphaltic oily mastic or asphalt
E Outer covering B
Glass fiber + Steel wire
Heat
insulation
Adhesive + Heat - resistant polyethylene foam + Adhesive tape
material A
Indoor Vinyl tape
Outer
Floor exposed Water-proof hemp cloth + Bronze asphalt
covering B
Outdoor Water-proof hemp cloth + Zinc plate + Oily paint
Note:
• When using polyethylene cover as covering material, asphalt roofing shall
not be required.
• No heat insulation must be provided for electric wires.
[Fig. 8.4.2] (P.4)
A Liquid pipe B Gas pipe
D Finishing tape E Insulater
[Fig. 8.4.3] (P.4)
C System analyzer
F Ball valve
I To oil trap kit
Restriction
B Piping
D Heat insulation material A
C Electric wire
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