Airtight Test, Evacuation, And Refrigerant Charging; Thermal Insulation Of Refrigerant Piping - Mitsubishi Electric CITY MULTI PUHY-P-YJM-A serie Installationshandbuch

• Determine the amount of additional refrigerant charge by using the formula,
and charge refrigerant additionally through the service port after completing
piping connection work.
• After completing work, tighten the service port and cap securely so as not to
generate any gas leakage. (Refer to the table on the below for appropriate
tightening torque.)
Appropriate tightening torque:
Outer diameter
Cap
of copper pipe
(N·m)
(mm)
ø9.52 15
ø12.7 20
ø15.88 25
ø19.05 25
ø25.4 25
ø28.58 25
Caution:
• Keep the valve closed until refrigerant charging to the pipes to be
added on site has been completed. Opening the valve before charging
the refrigerant may cause damage to the unit.
• Do not use a leak detection additive.
[Fig. 10.2.3] (P.7)
A Example of closure materials (field supply)
B Fill the gap at the site
Make sure to seal-off the space around areas where the wires and refrigerant
pipes enter the unit to ensure that small animals, rainwater, or snow cannot
enter the unit through such openings and cause damage to the unit.
Caution:
Make sure to seal-off the openings for the pipe and wire retrieval.
• Small animals, rainwater, or snow entering through the openings may
cause damage to the device.
(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 (Gupoflex, 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
malfunction.
2 Evacuation
Evacuate with the valve of the outdoor unit closed and evacuate both the
connection 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.8)
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
operating for five minutes.
18
Size of
Shaft Service port
hexagonal
(N·m) (N·m)
wrench (mm)
6 4
9 4
15 6 12
30 8
30 8
- - 16
Airtight test procedure
C Hi knob
F Gas pipe
I Valve
L Scale
O Outdoor unit
10.3. Airtight test, evacuation, and
refrigerant charging
1 Airtight test
Perform with the valve of the outdoor unit closed, and pressurize the
connection 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.8)
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 refrigerant (R410A), 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.
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
refrigerant 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 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 remaining in the cylinder.
[Fig. 10.3.3] (P.8)
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.8)
A Steel wire
C Asphaltic oily mastic or asphalt
E Outer covering B
Heat Glass fiber + Steel wire
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.8)
A Liquid pipe B Gas pipe
D Finishing tape E Insulator
[Fig. 10.4.3] (P.8)
C System analyzer
F Valve
I Outdoor unit
Restriction
B Piping
D Heat insulation material A
C Electric wire