4
2.  The standards for minimum room volume are as follows.
(1)  No partition (shaded portion)
(2)  When there is an effective opening with the adjacent room 
for ventilation of leaking refrigerant gas (opening without 
a door, or an opening 0.15% or larger than the respective 
floor spaces at the top or bottom of the door).
(3)  If an indoor unit is installed in each partitioned room and 
the refrigerant tubing is interconnected, the smallest room 
of course becomes the object. But when mechanical 
ventilation is installed interlocked with a gas leakage 
detector in the smallest room where the density limit is 
exceeded, the volume of the next smallest room becomes 
the object.
3.  The minimum indoor floor space compared with the 
amount of refrigerant is roughly as follows: (When the 
ceiling is 2.7 m high)
40.5
54.0
27.0
13.5
0.0
20100 3040 6070809010050
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
256.0
270.0
m
2
m
3
15
10
5
0
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
283.5
297.0
310.5
324.0
337.5
kg
Check of Density Limit
The room in which the air conditioner is to be installed 
requires a design that in the event of refrigerant gas 
leaking out, its density will not exceed a set limit.
The refrigerant (R410A), which is used in the air conditioner, 
is safe, without the toxicity or combustibility of ammonia, and 
is not restricted by laws imposed to protect the ozone layer. 
However, since it contains more than air, it poses the risk of 
suffocation if its density should rise excessively. Suffocation 
from leakage of refrigerant is almost non-existent. With the 
recent increase in the number of high density buildings, 
however, the installation of multi air conditioner systems is 
on the increase because of the need for effective use of floor 
space, individual control, energy conservation by curtailing heat 
and carrying power, etc.
Most importantly, the multi air conditioner system is able 
to replenish a large amount of refrigerant compared to 
conventional individual air conditioners. If a single unit of the 
multi air conditioner system is to be installed in a small room, 
select a suitable model and installation procedure so that if the 
refrigerant accidentally leaks out, its density does not reach the 
limit (and in the event of an emergency, measures can be made 
before injury can occur).
In a room where the density may exceed the limit, create an 
opening with adjacent rooms, or install mechanical ventilation 
combined with a gas leak detection device. The density is as 
given below.
Total amount of refrigerant (kg)
Min. volume of the indoor unit installed room (m
3
) 
< Density limit (kg/m
3
)
The density limit of refrigerant which is used in multi air 
conditioners is 0.3 kg/m
3
 (ISO 5149).
NOTE
1.  If there are 2 or more refrigerating systems in a single 
refrigerating device, the amount of refrigerant should be as 
charged in each independent device.
  For the amount of charge in this example:
  The possible amount of leaked refrigerant gas in rooms A, 
B and C is 10 kg.
The possible amount of leaked refrigerant gas in rooms D, 
E and F is 15 kg.
e.g., charged 
amount (10 kg)
Indoor unit
Outdoor unit
e.g., charged 
amount (15 kg)
Room A Room B Room C Room D Room E Room F
Outdoor unit
Refrigerant tubing
Indoor unit
Mechanical ventilation device – Gas leak detector
Refrigerant tubing
Outdoor unit
Indoor unit
Very 
small 
room
Small 
room
Medium 
room
Large room
Range below the 
density limit of 
0.3 kg/m³
(Countermeasures 
not needed)
Range above the 
density limit of 0.3 
kg/m³
(Countermeasures 
needed)
Total amount of refrigerant
Min. indoor volume
Min. indoor floor area
(when the ceiling is 2.7 m high)
PanaIndoor-337012Eng.indb4PanaIndoor-337012Eng.indb4 2012/03/2116:20:422012/03/2116:20:42