Refrigerant Piping System; Additional Refrigerant Charge; Calculation Of Additional Refrigerant Charge; Precautions Concerning Piping Connection And Valve Operation - Mitsubishi Electric CITY MULTI PUHY-HP-YHM-A Serie Manual De Instalación

9.2. Refrigerant piping system

Connection example
[Fig. 9.2.1] (P.3, 4)
A Outdoor unit
C Indoor unit
E Outdoor twinning kit
*1 The pipe sizes listed in columns A1 to A3 in this table correspond to the sizes for
the models listed in the unit 1, 2, and 3 columns. When the order of the models for
unit 1, 2, and 3 change, make sure to use the appropriate pipe size.
Precautions for outdoor unit combinations
Refer to [Fig. 9.2.2] for the positioning of twinning pipes.
[Fig. 9.2.2] (P.5)
<A> Make sure the pipes from the twinning pipe to the outdoor unit are sloped
downwards (towards the twinning pipes).
<B> When the piping on the outdoor unit side (from the twinning pipe) exceeds 2 m,
ensure a trap (gas pipe only) within 2 m. Make sure the height of the trap is 200
mm or more.
If there is no trap, oil can accumulate inside the pipe, causing a shortage of oil
and may damage the compressor.

10. Additional refrigerant charge

At the time of shipping, the outdoor unit is charged with refrigerant.
This charge does not include the amount needed for extended piping and additional
charging of each refrigerant line will be required on site. In order that future serv-
icing 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
provided on the outdoor unit.
10.1. 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 a guide to calculating the amount of additional
charging and charge the system accordingly.
• If the calculation results in a fraction of less than 0.1 kg, round up to the next
0.1 kg. For example, if the result of the calculation was 11.38 kg, round the
result up to 11.4 kg.
<Additional Charge>
Additional Liquid pipe size
refrigerant charge Total length of
=
ø19.05 × 0.29
(kg) (m) × 0.29 (kg/m)
Liquid pipe size
Total length of
+
ø9.52 × 0.06
(m) × 0.06 (kg/m)
<Example>
Indoor 1: 125 A: ø12.7 40 m
2: 100 B: ø9.52 10 m
3: 40 C: ø9.52 15 m
4: 32 D: ø9.52 10 m
5: 63
The total length of each liquid line is as follows:
ø12.7: A = 40 = 40 m
ø9.52: B + C + D + a + b + e = 10 + 15 + 10 + 10 + 5 + 10 = 60 m
ø6.35: c + d = 10 + 10 = 20 m
Therefore,
<Calculation example>
Additional refrigerant charge
= 40 × 0.12 + 60 × 0.06 + 20 × 0.024 + 3.5 = 12.4 kg
Value of α
Total capacity of connecting indoor units
Models ~ 80
Models 81 ~ 160
Models 161 ~ 330
Models 331 ~ 390
Models 391 ~ 480
Models 481 ~ 630
Models 631 ~ 650
B Branch
D Cap
Liquid pipe size Liquid pipe size
Total length of Total length of
+ +
ø15.88 × 0.2 ø12.7 × 0.12
(m) × 0.2 (kg/m) (m) × 0.12 (kg/m)
Liquid pipe size
Total length of
+ + α
ø6.35 × 0.024
(m) × 0.024 (kg/m)
a: ø9.52 10 m
At the
b: ø9.52 5 m
conditions
c: ø6.35 10 m
below:
d: ø6.35 10 m
e: ø9.52 10 m
α
2.0 kg
2.5 kg
3.0 kg
3.5 kg
4.5 kg
5.0 kg
6.0 kg
<C> Slope of twinning pipes
Make sure the slope of the twinning pipes are at an angle within ±15° to the
ground.
If the slope exceeds the specified angle, the unit may be damaged.
<D> Pipe connection example
A Downward slope
C Indoor unit
E Within 2 m
G Slope of the twinning pipes are at an angle within ±15° to the ground
H Pipes on site
J Straight run of pipe that is 500 mm or more
10.2. Precautions concerning piping connec-
tion and valve operation
• Conduct piping connection and valve operation accurately and carefully.
• Removing the pinched connecting pipe
When shipped, a pinched connecting pipe is attached to the on-site liquid and
gas valves to prevent gas leakage.
Take the following steps 1 through 4 to remove the pinched connecting pipe
before connecting refrigerant pipes to the outdoor unit.
1 Check that the refrigerant service valve is fully closed (turned clockwise all
the way).
2 Connect a charging hose to the service port on the liquid/gas refrigerant
service valve, and extract the gas in the pipe section between the refriger-
ant service valve and the pinched connecting pipe (Tightening torque
12 N·m).
3 After vacuuming gas from the pinched connecting pipe, sever the pinched
connecting pipe at the location shown in [Fig.10.2.1] and drain the
refrigerant.
4 After completing 2 and 3 heat the brazed section to remove the pinched
connecting pipe.
[Fig. 10.2.1] (P.6)
<A> Refrigerant service valve (liquid side/brazed type)
<B> Refrigerant service valve (gas side/brazed type)
A Shaft
Fully closed at the factory, when connecting the piping, and when vacuuming.
Open fully after these operations are completed.
<When opening>
• Turn the shaft counterclockwise with a hexagonal wrench.
• Turn around the shaft until it stops.
<When closing>
• Turn the shaft clockwise with a hexagonal wrench.
• Turn around the shaft until it stops.
B Service port
Available for gas venting of the pinched connecting pipe, or vacuuming in the
refrigerant pipes on the site.
(Tightening torque 12 N·m)
C Cap
Remove the cap before operating the shaft. Be sure to return it to the original
position after completing the operation.
D Pinched connecting pipe severing portion
E Pinched connecting pipe brazing portion
Warning:
• The section of the pipe on the unit between the two refrigerant service
valves is filled with gas. Extract the gas in the above-mentioned pipe
section before heating the brazed section to remove the refrigerant service
valve connecting pipe.
- If the brazed section is heated without first extracting the gas, the pipe may
burst or the connecting pipe may blow off causing serious injury.
Caution:
• Place a wet towel on the refrigerant service valve before heating the brazed
section to keep the temperature of the valve from exceeding 120 ˚C.
• Direct the flame away from the wiring and metal sheets inside the unit to
prevent heat damage.
B Upward slope
D Trap (gas pipe only)
F Twinning pipe
I Twinning kit
15