Mitsubishi Electric PUMY-P250YBM Technical & Service Manual page 120

Branch box Method
Connection Examples
(Connecting to 12 Indoor Units)
Total piping length
Farthest piping length (L)
Permissible
Piping length between outdoor unit and branch boxes
length
(one-way)
Farthest branch box from the first joint
Farthest piping length after branch box (R)
Total piping length between branch boxes and indoor units
In indoor/outdoor section (H) *1
Permissible
In branch box/indoor unit section
height difference
(one-way)
In each branch unit (h2)
In each indoor unit (h3)
Number of bends
*1 Branch box should be placed within the level between the outdoor unit and indoor units.
■ Select Each Section of Refrigerant Piping
■ Additional refrigerant charge
Additional refrigerant charge
Refrigerant for the extended piping is not included
in the outdoor unit when the unit is shipped from
the factory. Therefore, charge each refrigerant
piping system with additional refrigerant at the
installation site. In addition, in order to carry out
service, enter the size and length of each liquid
pipe and additional refrigerant charge amounts in
the spaces provided on the "Refrigerant amount"
plate on the outdoor unit.
* When the unit is stopped, charge the unit with
the additional refrigerant through the liquid stop
valve after the pipe extensions and indoor units
have been vacuumized.
When the unit is operating, add refrigerant to the
gas check valve using a safety charger. Do not
add liquid refrigerant directly to the check valve.
Calculation of additional refrigerant charge
• Calculate the additional charge using the liquid
pipe size and length of the extended piping and
total capacity of connected indoor units.
• Calculate the additional refrigerant charge using
the procedure shown to the right, and charge with
the additional refrigerant.
• For amounts less than 0.1 kg, round up the
calculated additional refrigerant charge.
(For example, if the calculated charge is 6.01 kg,
round up the charge to 6.1 kg.)
OCH760
A Outdoor unit
B Branch box
C Indoor unit
c1
c2
E
D
b1
B
H
a1
h1
a2 a3
C C
h3
c1 + c2 + b1 + b2 + b3 + a1 + a2 + a3 + a4 + a5 + a6 + a7 + a8 + a9 + a10
+ a11 + a12
c1 + c2 + b3 + a12
c1 + c2 + b1 + b2 + b3
c2 + b3
a12
a1 + a2 + a3 + a4 + a5 + a6 + a7 + a8 + a9 + a10 + a11 + a12
H [
H [
h1 + h2
h2
[
h3 [
| c1 + b1 + a1 |, | c1 + b1 + a2 |, | c1 + b1 + a3 |, | c1 + b1 + a4 |, | c1 + b1 + a5 |,
| c1 + c2 + + b2 + a6|, |c1 + c2 + b2 + a7|, |c1 + c2 + b2 + a8|, |c1 + c2 + b2 + a9|,
|c1 + c2 + b2 + a10|, |c1 + c2 + b3 + a11|, |c1 + c2 + b3 + a12|
Refer to 7-2-2.
<Additional charge>
Calculation of refrigerant charge
Pipe size Pipe size
Liquid pipe Liquid pipe
+ +
ø6.35 ø9.52
(m) × 19.0 (g/m) (m) × 50.0 (g/m) (m) × 92.0 (g/m)
Included refrigerant amount when shipped from the factory
Model name Included refrigerant amount
PUMY-P250YBM
PUMY-P300YBM
<Example>
Outdoor model: PUMY-P250YBM
Indoor 1: model 50
2: model 50
3: model 50
4: model 50
5: model 50
6: model 42
The total length of each liquid line is as follows:
ø9.52 : b1 + b2 + c1 + c2 = 30m
ø6.35 : a1 + a2 + a6 + a7 + a8 +a9 = 75m
The total capacity of connected indoor unit is as follows:
50 (5.0kW) + 50 (5.0kW) + 50 (5.0kW) + 50 (5.0kW) + 50 (5.0kW) + 42 (4.2kW) = 292 (29.2kW)
<Calculation example>
Additional refrigerant charge
50.0 19.0
30 × + 75 × + 3.5 = 6.5 kg (rounded up)
1000 1000
120
D The first joint
E The second joint
b2
B
a4 a5 a6 a7 a8 a9
C C C C C
240 m
[
[ 80 m
[ 95 m
[ 30 m
[ 25 m
50 m (In case of outdoor unit is set higher than indoor unit)
40 m (In case of outdoor unit is set lower than indoor unit)
[ 15 m
15 m
12 m
Pipe size Total capacity of con-
Liquid pipe nected indoor units
+
ø12.7 – 16.0 kW
16.1 kW – 27.0 kW
27.1 kW – 31.0 kW
31.1 kW – 34.0 kW
34.1 kW – 36.5 kW
36.6 kW – 39.0 kW
39.1 kW – 41.0 kW
41.1 kW –
9.3 kg
b1 + b2 + c1 + c2: ø9.52 30 m
a1: ø6.35 15 m
a2: ø6.35 10 m
a6: ø6.35 10 m
a7: ø6.35 10 m
a8: ø6.35 15 m
a9: φ6.35 15m
L
b3
B
h2
a11 a12
R
a10
C
C
C
[ 145 m
[ 23
Amount for the
indoor units
2.5 kg
3.0 kg
3.5 kg
4.0 kg
4.5 kg
5.0 kg
5.5 kg
6.1 kg
At the
conditions
below: