Additional Refrigerant Charge; Calculation Of Additional Refrigerant Charge; Caution For Piping Connection/Valve Operation; Airtight Test, Evacuation, And Refrigerant Charging - Mitsubishi Electric CITY MULTI PUHY-TMU-A Installation Manual

8. Additional Refrigerant Charge

At the time of shipping, the outdoor unit is charged with the refrigerant. As this
charge does not include the amount needed for extended piping, additional charg-
ing for each refrigerant line will be required on site. In order that future servicing
may be properly provided, always keep a record of the size and length of each
refrigerant line and the amount of additional charge by writing it in the space pro-
vided on the outdoor unit.
8.1. Calculation of Additional Refrigerant
Charge
• Calculate the amount of additional charge based on the length of the piping
extension and the size of the refrigerant line.
• Use the table to the right as guide to calculating the amount of additional charg-
ing and charge the system according.
• If the calculation results of the calculation result in a fraction of less than 0.1 kg
[4 oz]. For example, if the result of the calculation was 11.06 kg [391 oz], round
the result up to 11.1 kg [392 oz].
<Additional Charge>
Liquid pipe size
Additional
refrigerant charge Total length of
=
ø12.7 (mm) × 0.12 (kg/m)
ø1/2 [in] × 1.29 [oz/ft]
(kg) [oz]
<Example>
Indoor 1: 16 A: ø12.7 (1/2) 40 m [131 ft]
2: 40 B: ø12.7 (1/2) 10 m [33 ft]
3: 16 C: ø12.7 (1/2) 5 m [16 ft]
4: 12 D: ø9.52 (3/8) 5 m [16 ft]
5: 12
The total length of each liquid line is as follows:
ø12.7 [1/2]: A + B + C = 40 [131]+ 10 [33] + 5 [16] = 55 m [180 ft]
ø9.52 [3/8]: D + a + b + c = 5 [16] + 10 [33] + 10 [33] + 10 [33] = 35 m [115 ft]
ø6.35 [1/4]: d + e = 5 [16] + 10 [33] = 15 m [49 ft]
Therefore,
<Calculation example>
Additional refrigerant charge
= 55 [180] × 0.12 [1.29] + 35 [115] × 0.06 [0.65] + 15 [49] × 0.024 [0.26] + 2 [71]
= 11.1 kg [392 oz]
Value of α
Total capacity of connecting indoor units
to Model 32
Models 33 to 64
Models 65 to 130
8.2. Caution for piping connection/valve
operation
• Conduct piping connection and valve operation accurately.
• The gas side connecting pipe is being assembled for shipment.
1 For brazing to the connecting pipe with flange, remove the connecting pipe
with flange from the ball valve, and braze it at the outside of the unit.
2 During the time when removing the connecting pipe with flange, remove
the seal attached on the back side of this sheet and paste it onto the flange
surface of the 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. 8.2.1] (P.3)
• 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 using the formula,
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.
8
Liquid pipe size Liquid pipe size
Total length of Total length of
+ +
ø9.52 (mm) × 0.06 (kg/m) ø6.35 (mm) × 0.024 (kg/m)
ø3/8 [in] × 0.65 [oz/ft] ø1/4 [in] × 0.26 [oz/ft]
a: ø9.52 10 m [32 ft]
At the
b: ø9.52 10 m [32 ft]
conditions
c: ø9.52 10 m [32 ft]
d: ø6.35 5 m [16 ft] below:
e: ø6.35 10 m [32 ft]
α
1.0 kg [36 oz]
1.5 kg [53 oz]
2.0 kg [71 oz]
[Fig. 8.2.2] (P.3)
(Unit: mm [in])
<A> [Ball valve (gas side)]
(This figure shows the valve in the fully open state.)
<B> [Ball valve (liquid side)]
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)
[Manufacturer: Nichiasu corporation]
[Type: T/#1991-NF]
D Connecting pipe (Accessory)
[Use packing and securely install this pipe to the valve flange so that gas leakage
will not occur. (Tightening torque: 25 N·m (250 kg·cm)) Coat both surfaces of the
packing with refrigerator oil (Ester oil, ether oil or alkylbenzene [small amount]).]
E Open (Operate slowly)
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
+ α
[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: 55 N·m (550 kg·cm)
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 ø12.7 [1/2]
J ø25.4 [1] (PUHY-80TMU-A)
ø28.58 [1-1/8] (PUHY-100TMU-A)
K Field piping
[Braze to the connecting pipe. (When brazing, use unoxidized brazing.)]
L Close-packed packing
M Hollow packing
Appropriate tightening torque by torque wrench:
Copper pipe external dia. (mm [in])
ø6.35 [1/4]
ø9.52 [3/8]
ø12.7 [1/2]
ø15.88 [5/8]
ø19.05 [3/4]
Tightening angle standard:
Pipe diameter (mm [in])
ø6.35, ø9.52 [1/4, 3/8]
ø12.7, ø15.88 [1/2, 5/8]
ø19.05 [3/4]
[Fig. 8.2.3] (P.3)
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 connecting pipe from the ball valve and braze it out-
side the unit.
- Brazing the connecting 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.
• Do not use a leak detection additive.
8.3. 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
gas pipe service ports.)
[Fig. 8.3.1] (P.3)
A Nitrogen gas
D Lo Knob
G Liquid pipe
J Service port
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
20 to 35
B To indoor unit C System analyzer
E Hi Knob F Ball valve
H Gas pipe I Outdoor unit