2
2
- 22
Design of 3-WAY FLOW LOGIC
2. System Design
■
■
Checking of limit density
The limit density judgment is made based on the room
with the indoor unit having the smallest capacity in the
system after extension.
The volume of the room where a type 28 indoor unit is
used (connected to tubing L11) is calculated as follows:
floor area 15 m
2
×
Ceiling height 2.7 m = 40. 5 m
3
. From
the graph below, the minimum room volume for 53.69 kg
of refrigerant is 175 m
3
(floor area 65 m
2
). Therefore an
opening for ventilation is required.
<Judgment by calculation>
Total refrigerant charge for the refrigeration equipment (kg)
Smallest room volume of all rooms where indoor units are
installed (m
3
)
=
53.69 (kg)
= 1.33 (kg/m
3
) 0.30 (kg/m
3
)
40.5 (m
3
)
In this case, an opening is required for ventilation.
WARNING
Always check the gas den-
sity limit for the room in
which the unit is installed.
■
■
Check of Limit Density
When installing an air conditioner in a room, it is neces-
sary to ensure that even if the refrigerant gas acciden-
tally leaks out, its density does not exceed the limit
level for that room.
If the density could exceed the limit level, it is neces-
sary to provide an opening between the unit and the
adjacent room, or to install mechanical ventilation
which is interlocked with the leak detector.
(Total refrigerant charged amount: kg)
(Min. indoor volume where the indoor unit is installed: m
3
)
Limit density 0.3 (kg/m
3
)
The limit density of refrigerant which is used in this unit
is 0.3 kg/m
3
(ISO 5149).
The shipped outdoor unit comes charged with the
amount of refrigerant fixed for each type, so add it to the
amount that is charged in the field. (For the refrigerant
charge amount at shipment, refer to the unit’s name-
plate.)
Minimum indoor volume & floor area as against the
amount of refrigerant is roughly as given in the follow-
ing table.
40.5
54.0
20
30
40
50
60
70
80 kg
67.5
81.0
94.5
108.0
121.5
135.0
148.5
162.0
175.5
189.0
202.5
216.0
229.5
243.0
256.5
270.0
m
2
m
3
Total amount of refrigerant
Min. indoor floor area
(when the ceiling is 2.7 m high)
Min. indoor volume
Range below the
density limit of
0.3 kg/m
3
(Countermeasures
not needed)
Range above the
density limit of
0.3 kg/m
3
(Countermeasures
needed)
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
CAUTION
Pay special attention to any
location, such as a basement,
etc., where leaking refrigerant
can accumulate, since refrig-
erant gas is heavier than air.
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