Airtight Test, Evacuation, And Refrigerant Charging - Mitsubishi Electric Y Série 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 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]
B
B
C
LO
A
C
D
(1) After pressurizing to the design pressure (4.15 MPa [602 psi]) 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 refrigerant 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] [0.0943 psi/5 Torr], 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 [0.01886 psi/1.0 Torr], water might have entered. Apply pressure to dry nitrogen gas up to 0.05 MPa [7.25 psi] 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]
D
N
N
O
A
LO HI
G
B C
H
K
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 [3 oz].)
• 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] [0.00943 psi/0.5 Torr] or below 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 siphon pipe, charge the liquid refrigerant by turning the cylinder upside-down as shown in Fig.10.3.3. If the cylinder has a siphon pipe like that
shown on the right of Fig.10.3.3, 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]
<If the cylinder does not have a siphon pipe, charge with the refrigerant cylinder upside-down.>
A Siphon pipe
12
F
G
H
I
HI
E
J
Airtight test procedure
E
F
I
M
J
L
A B
Nitrogen gas To indoor unit
D E
Lo knob Hi knob
G H
Liquid pipe 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.
• If a flammable gas or air (oxygen) is used as the pressurization
gas, it may catch fire or explode.
A System analyzer B Lo 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
A
C
System analyzer
F
Valve
I
Outdoor unit
Restriction
C Hi knob
F Gas pipe
I Valve
L Scale
O Outdoor unit