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3
SM830063
Service Procedures
6. Check of Density Limit
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NOTE
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 R-407C which is used in the air condi-
tioner is safe, without the toxicity or combustibility of
ammonia, and is not restricted by laws to be imposed
which 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
R-407C 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 curtail-
ing heat and carrying power etc.
Most importantly, the multi air conditioner system is able
to replenish a large amount of refrigerant compared with
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 emer-
gency, 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 R-407C which is used in multi
air conditioners is 0.3 kg/m
3
.
Important
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.
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.
NOTE
>
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e.g., charged
amount (10 kg)
Outdoor unit
Indoor unit
Room A Room B Room C Room D Room E Room F
e.g.,
charged amount (15 kg)
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 a 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.
Outdoor unit
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Refrigerant tubing
Indoor unit
Refrigerant tubing
Outdoor unit
Very
small
room
Indoor unit
Small
room
Medium
room
Large room
Mechanical ventilation device - Gas leak detector
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3 : The minimum indoor floor space com-
pared with the amount of refrigerant is
roughly as follows.
(When the ceiling is 2.7 m high)
10
13.5
27.0
40.5
54.0
67.5
81.0
94.5
108
121.5
135
5
10
15
20
25
30
35
40
45
50
m
3
m
2
Total amount of refrigerant
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Min. indoor floor area
(when the ceiling is 2.7 m high)
Min. indoor volume
20
30
40 kg
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)
NOTE
