Airtight Test, Evacuation, And Refrigerant Charging; Airtight Test - Mitsubishi Electric PQHY-P-YHM-A Serie Manual De Instalación

Appropriate tightening torque:
Outer
diameter of
Cap (N·m) Shaft (N·m)
copper pipe
(mm)
ø9.52 15
ø12.7 20
ø15.88 25
ø19.05 25
ø25.4 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.
(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 fl are connection parts, brazed
parts, and other parts that may leak with a bubbling agent (Kyubofl ex, 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 heat source unit closed and evacuate both
the connection piping and the indoor unit from the service port provided on
the valve of the heat source unit using a vacuum pump. (Always evacuate
from the service port of both the high-pressure pipe and the low-pressure
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 high-pressure pipe, and adjust
the low-pressure piping to obtain an appropriate amount of the refrigerant
during operation.
* Never perform air purging using refrigerant.
[Fig. 10.3.2] (P.9)
A System analyzer B Low knob
D Valve E Low-pressure pipe
G Service port H Three-way joint
J Valve K R410A cylinder
M Vacuum pump N To indoor unit
Size of
hexagonal Service port
wrench (N·m)
(mm)
6 4
9 4
15 6 12
30 8
30 8
Airtight test procedure
C Hi knob
F High-pressure pipe
I Valve
L Scale
O Heat source unit
10.3. Airtight test, evacuation, and
refrigerant charging

1 Airtight test

Perform with the valve of the heat source unit closed, and pressurize the
connection piping and the indoor unit from the service port provided on the
valve of the heat source unit. (Always pressurize from both the high-pressure
pipe and the low-pressure pipe service ports.)
[Fig. 10.3.1] (P.9)
A Nitrogen gas B To indoor unit
D Low knob E Hi knob
G Low-pressure pipe H High-pressure 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 fl ammable gas or air (oxygen) is used as the pressurization
gas, it may catch fi re or explode.
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 fl ow 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 fi ve 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
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 specifi cations. 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.9)
A Syphon pipe B In case of the R410A cylinder having no syphon pipe.
C System analyzer
F Valve
I Heat source unit
Restriction
23