Refrigerant Charging; Thermal Insulation Of Refrigerant Piping - Mitsubishi Electric CITY MULTI PUHY-P-THMU-A Manuel D'installation

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
HI
LO
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] [0.0943 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

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]
C
B A
D
E
A Steel wire
C Oily mastic asphalt 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
E
F
I
M
J
L
B Piping
D Heat insulation material A
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
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]
B
A
C
D
E
A Liquid pipe B Gas pipe
D Finishing tape E Insulator
[Fig. 10.4.3]
C Hi knob
F Gas pipe
I Valve
L Scale
O Outdoor unit
E
E
A
B
D
C Electric wire
13