Caution For Piping Connection/Valve Operation; Refrigerant Piping System; Additional Refrigerant Charge; Airtight Test, Evacuation, And Refrigerant Charging - Mitsubishi Electric PUH-8 Installation Manual

9 Always use a non-oxidizing brazing material for brazing the parts. If a non-
oxidizing brazing material is not used, it could cause clogging or damage to
the compressor unit.
0 Never perform outdoor unit piping connection work when it is raining.
Warning:
When installing or relocating the unit, make sure that no substance other
than the specified refrigerant (R22) enters the refrigerant circuit.
- Any presence of foreign substance such as air can cause abnormal pressure
rise or explosion.
7.2. Caution for piping connection/valve
operation
• Conduct piping connection and valve operation accurately.
• Remove the bypass tube that is connected to the valve before connecting the
valve to the pipe on site.
• Follow the procedures below to connect the valve on the gas side of the PUH-
8, 10 models with the supplied flange.
1 For brazing to the connection pipe with flange, remove the by-pass tube
with flange from the ball valve, and braze it at the outside of the unit.
2 During the time when removing the by-pass tube with flange, seal the flange
surface of ball valve to prevent the entry of dust into the valve.
3 The refrigerant circuit is closed with a round, close-packed packing at the
shipment to prevent gas leak between flanges. As no operation can be
done under this state, be sure replace the packing with the hollow packing
attached at the piping connection.
4 At the mounting of the hollow packing, wipe off dust attached on the flange
sheet surface and the packing. Coat refrigerating machine oil (Ester oil,
ether oil or alkylbenzene [small amount]) onto both surfaces of the pack-
ing.
[Fig. 7.2.1] (P.4)
• After evacuation and refrigerant charge, ensure that the handle is fully open. If
operating with the valve closed, abnormal pressure will be imparted to the
high- or low-pressure side of the refrigerant circuit, giving damage to the com-
pressor, four-way valve, etc.
• Determine the amount of additional refrigerant charge by referring the refriger-
ant charge table, and charge refrigerant additionally through the service port
after completing piping connection work.
• After completing work, tighten the service port and cap securely not to gener-
ate gas leak.
[Fig. 7.2.2] (P.4)
<A> [Ball valve (Flange type)]
(This figure shows the valve in the fully open state.)
<B> [Ball valve (Flare type)]
A Valve stem
[Fully closed at the factory, when connecting the piping, when evacuating, and
when charging additional refrigerant. Open fully after the operations above are
completed.]
B Stopper pin [Prevents the valve stem from turning 90° or more.]
C Packing (Accessory)
D Connection pipe (Accessory)
[Use packing and securely install this pipe to the valve flange so that gas leakage
will not occur. (Tightening torque: 50 N·m (500 kg·cm)) Coat both surfaces of the
packing with refrigerator oil (Ester oil, ether oil or alkylbenzene [small amount]).]
E Open (Operate slowly)

8. Additional refrigerant charge

8.1. Additional refrigerant charge
The amount of refrigerant (R22) in the outdoor unit at factory is appropriate for 7.5
meter long refrigerant pipe.
Therefore, refer to table below and charge the corresponding amount of refrigerant
according to connection piping length.
Piping length (one way)
Model
7.5m 10m 15m 20m
PUH-8
0 0.3 0.9 1.5
PUH-10
0 0.3 0.9 1.5
Note:
If there is an insufficient amount of refrigerant in the system, the unit will
behave in one of the following ways: 1) the discharge temperature of the unit
rises abnormally high, which is detected as an error, and the unit comes to a
stop; 2) the discharge temperature of the compressor rises abnormally high,
the unit goes into the unload operation, which appears as the P8 error on the
display, and the unit comes to a stop; or 3) the built-in thermostat on the
compressor goes off and stops the compressor. In either case, replenish
and adjust the refrigerant. Once the unit goes into the unload operation, it
will take a long time until normal operation can be restored.
Additional refrigerant charge (R-22) ···· kg
25m 30m 35m 40m 45m
2.1 2.6 3.2 3.8 4.4
2.1 2.6 3.2 3.8 4.4
F Cap, copper packing
[Remove the cap and operate the valve stem. Always reinstall the cap after op-
eration is completed. (Valve stem cap tightening torque: 25 N·m (250 kg·cm) or
more)]
G Service port
[Use this port to evacuate the refrigerant piping and add an additional charge at
the site.
Open and close the port using a double-ended wrench.
Always reinstall the cap after operation is completed. (Service port cap tightening
torque: 14 N·m (140 kg·cm) or more)]
H Flare nut
[Tightening torque:
PUH-8, 10
Loosen and tighten this nut using a double-ended wrench.
Coat the flare contact surface with refrigerator oil (Ester oil, ether oil or alkylbenzene
[small amount]).]
I Field piping
[Braze to the connection pipe. (When brazing, use unoxidized brazing.)]
J Close-packed packing
K Hollow packing
Appropriate tightening torque by torque wrench:
Copper pipe external dia. (mm)
ø6.35
ø9.52
ø12.7
ø15.88
ø19.05
Tightening angle standard:
Pipe diameter (mm)
ø6.35, ø9.52
ø12.7, ø15.88
[Fig. 7.2.3] (P.4)
Note:
If a torque wrench is not available, use the following method as a standard:
When you tighten the flare nut with a wrench, you will reach a point where
the tightening torque will abrupt increase. Turn the flare nut beyond this point
by the angle shown in the table above.
Caution:
• Always remove the connection pipe from the ball valve and braze it out-
side the unit.
- Brazing the connection pipe while it is installed will heat the ball valve and
cause trouble or gas leakage. The piping, etc. inside the unit may also be
burned.
• Use ester oil, ether oil or alkylbenzene (small amount) as the refrigerator
oil to coat flares and flange connections.
- The refrigerator oil will degrade if it is mixed with a large amount of mineral
oil.

7.3. Refrigerant piping system

Connection Example
[Fig. 7.3.1] (P.4)
Å Outdoor unit
ı Gas pipe size
Ç Liquid pipe size
Î Indoor unit
Caution:
• Pipe bending can be up to a maximum of 8 places.
8.2. Airtight test, evacuation, and refrigerant
charging
1 Airtight test
Perform with the stop valve of the outdoor unit closed, and pressurize the con-
nection piping and the indoor unit from the service port provided on the stop
valve of the outdoor unit. (Always pressurize from both the liquid pipe and the
50m gas pipe service ports.)
5.0
[Fig. 8.2.1] (P.5)
5.0
A Nitrogen gas
D Lo Knob
G Liquid pipe
J Service port
Liquid side: 80 N·m (800 kg·cm)
Tightening torque (N·m) / (kg·cm)
14 to 18 / 140 to 180
35 to 42 / 350 to 420
50 to 57.5 / 500 to 575
75 to 80 / 750 to 800
100 to 140 / 1000 to 1400
Tightening angle (°)
60 to 90
30 to 60
(1) Single
• Connecting with PEH-8, 10
• Connecting with PEH-16, 20
B To indoor unit C System analyzer
E Hi Knob F Stop valve
H Gas pipe I Outdoor unit
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