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5. Refrigerant piping design
1. Warnings on refrigerant leakage
Check of concentration limit
The room in which the air conditioner is to be installed requires a design that ensures that the concentration of
refrigerant gas will not exceed a set limit if there is a leak.
Refrigerant R-410A which is used in the air conditioner is safe, without the toxicity or combustibility of ammonia,
and is not restricted by laws that protect the ozone layer. However, since it contains more than air, it poses the
risk of suffocation if its concentration should rise excessively. Suffocation from leakage of R-410A is almost non-
existent. With the recent increase in the number of high concentration 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 contain 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 concentration
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 concentration may exceed the limit, create an opening to adjacent rooms, or install mechanical
ventilation combined with a gas leak detection device. The concentration is as given below.
Total amount of refrigerant (kg)
Min. volume of the indoor unit installed room (m³)
≤ Concentration limit (kg/m³)
The concentration limit of R-410A which is used in multi air conditioners is 0.3 kg/m³.
Note 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 piping is interconnected, the smallest
room is the critical room. But when a mechanical
ventilation device is installed in combination with a gas
leak detector in the smallest room where the density
limit is exceeded, the volume of the next smallest
room is used.
Note 1: If there are 2 or more refrigeration systems in
a single refrigeration device, the amounts 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.
Mechanical ventilation device - gas leak detector
Outdoor unit
e.g. charged amount (15 kg)
e.g. charged
amount (10 kg)
Room A
Room B
Room C Room D Room E Room F
Indoor unit
Outdoor unit
Indoor unit
Refrigerant piping
Refrigerant piping
Outdoor unit
Indoor unit
Large room
Medium room
Small
room
Very
small
room