Airtight Test, Evacuation, And Refrigerant Charging; Thermal Insulation Of Refrigerant Piping - Mitsubishi Electric CITY MULTI PUHY-HP-YHM-A Manuel D'installation

10.3. Airtight test, evacuation, and refrigerant
charging
1 Airtight test
Perform with the valve of the outdoor unit closed, and pressurize the connec-
tion piping and the indoor unit from the service port provided on the valve of
the outdoor unit. (Always pressurize from both the liquid pipe and the gas pipe
service ports.)
[Fig. 10.3.1] (P.7)
A Nitrogen gas B To indoor unit
D Low knob E Hi knob
G Liquid pipe H Gas pipe
J Service port
Observe the following restrictions when conducting an air tightness test to prevent
negative effects on the refrigerating machine oil. Also, with nonazeotropic refriger-
ant (R410A), gas leakage causes the composition to change and affects perform-
ance. Therefore, perform the airtightness test cautiously.
(1) After pressurizing to the design pressure (4.15 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, 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.
Caution:
Only use refrigerant R410A.
- The use of other refrigerants such as R22 or R407C, which contains chlorine,
will deteriorate the refrigerating machine oil or cause the compressor to malfunc-
tion.
2 Evacuation
Evacuate with the valve of the outdoor unit closed and evacuate both the con-
nection piping and the indoor unit from the service port provided on the valve
of the outdoor unit using a vacuum pump. (Always evacuate from the service
port of both liquid pipe and gas pipe.) After the vacuum reaches 650 Pa [abs],
continue evacuation for at least one hour or more. Then, stop the vacuum
pump and leave it for 1 hour. Ensure the degree of vacuum has not increased.
(If the degree of vacuum increase is larger than 130 Pa, water might have
entered. Apply pressure to dry nitrogen gas up to 0.05 MPa and vacuum
again.) Finally, seal in with the liquid refrigerant through the liquid pipe, and
adjust the gas piping to obtain an appropriate amount of the refrigerant during
operation.
* Never perform air purging using refrigerant.
[Fig. 10.3.2] (P.7)
A System analyzer B Low knob
D Valve E Liquid pipe
G Service port H Three-way joint
J Valve K R410A cylinder
M Vacuum pump N To indoor unit
Note:
• Always add an appropriate amount of refrigerant. Also always charge
the system with liquid refrigerant.
• 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 65 Pa [abs] or below after operat-
ing for five minutes.
C System analyzer
F Valve
I Outdoor unit
Airtight test procedure
C Hi knob
F Gas pipe
I Valve
L Scale
O Outdoor unit
• If a flammable gas or air (oxygen) is used as the pressurization
gas, it may catch fire or explode.
3 Refrigerant Charging
Do not use refrigerant other than the type indicated in the manuals pro-
vided with the unit and on the nameplate.
- Doing so may cause the unit or pipes to burst, or result in explosion or fire
during use, during repair, or at the time of disposal of the unit.
- It may also be in violation of applicable laws.
- MITSUBISHI ELECTRIC CORPORATION cannot be held responsible for
malfunctions or accidents resulting from the use of the wrong type of refrig-
erant.
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 in Fig.10.3.3. If the cylinder
has a syphon pipe like that shown in the picture on the right, the liquid refriger-
ant 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 re-
frigerant remaining in the cylinder.
[Fig. 10.3.3] (P.7)
A Syphon pipe B In case of the R410A cylinder having no syphon pipe.

10.4. Thermal insulation of refrigerant piping

Be sure to add 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 in the ceiling plenum.
[Fig. 10.4.1] (P.7)
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. 10.4.2] (P.7)
A Liquid pipe B Gas pipe
D Finishing tape E Insulator
[Fig. 10.4.3] (P.7)
Restriction
B Piping
D Heat insulation material A
C Electric wire
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