Refrigerant Charging - Mitsubishi Electric PURY-P72TJMU-A(-BS) Manuel D'installation

Airtight test procedure
(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 fl are connection parts,
brazed parts, fl anges, 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 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 the high-pressure pipe and the low-pressure 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 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]
D
N
N
O
A
LO HI
G
B C
H
A System analyzer B Lo 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
[Fig. 10.3.3]
<If the cylinder does not have a siphon pipe, charge with the refrigerant cylinder upside-down.>
A Siphon pipe
E
F
I
M
K
J
L
C Hi knob
F High-pressure pipe
I Valve
L Scale
O Outdoor unit
Restriction
• 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 [3 oz].)
• 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] [0.00943 psi/
0.5 Torr] 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 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 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.
A
15