Airtight Test, Evacuation, And Refrigerant Charging - Mitsubishi Electric CITY MULTI PUHY-P-YEM-A Installationshandbuch

[Remove the cap and operate the valve stem. Always reinstall the cap after op-
eration is completed. (Valve stem cap tightening torque: 25 N·m or more)]
G Service port
[Use this port to evacuate the refrigerant piping and add an additional charge at
the site.
Open and close the port using a double-ended wrench.
Always reinstall the cap after operation is completed. (Service port cap tightening
torque: 14 N·m or more)]
H Flare nut
[Tightening torque: 55 N·m
Loosen and tighten this nut using a double-ended wrench.
Coat the flare contact surface with refrigerating machine oil (Ester oil, ether oil or
alkylbenzene [small amount])]
I ø12.7
J ø25.4 (PU(H)Y-P200)
ø28.58 (PU(H)Y-P250)
ø31.75 (PU(H)Y-P315)
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)
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. 8.2.3] (P.3)
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 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 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.
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
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.
• 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.
8.3. Airtight test, evacuation, and refrigerant
charging
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 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.)
• 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
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
C System analyzer
F Ball valve
I Outdoor unit
Restriction
9