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G Special Attention Regarding Refrigerant Gas Leakage
Pay an attention to the critical gas concentration to avoid accidental refrigerant gas leakage before
installing air conditioning systems.
Totally Charged Refrigerant Quantity in System (kg)
Room Space for each Indoor Unit (m
In the case that the calculated critical concentration is bigger than 0.3kg/m
1) Provide a gas leakage detector and exhaust fan(s) controlled by its gas leakage detector.
2) Provide each effective opening at the wall or door for ventilation to next door so that the critical gas
concentration can be maintained lower than the above value.
(Provide an opening more than 0.15% of floor surface at the lower part of a door.)
Stop Valve (Gas Line)
1. Maximum Permissible Concentration of HFC GAS R410A
The refrigerant R410A is an incombustible and non-toxic gas.
However, if leakage occurs and gas fills a room, it may cause suffocation. The maximum permissible
concentration of HFC gas, R410A in air is 0.3kg/m
standard (KHK S 0010) by the KHK (High Pressure Gas Protection Association) Japan. Therefore, some
effective measure must be taken to lower the R410A concentration in air below 0.3kg/m
As for R410A, this consideration is applied similarly.
2. Calculation of Refrigerant Concentration
(1) Calculate the total quantity of refrigerant R (kg) charged in the system connecting all the indoor units of
objective rooms.
(2) Calculate the room volume V (m
(3) Calculate the refrigerant concentration C (kg/m
R: Total Quantity of Charged Refrigerant (kg)
V: Room Volume (m
= C: Refrigerant Concentration
If local codes or regulations are specified, follow them.
<Example>
British Standard BS4434 1989 Commercial office
Building Class D Occupancy C=0.17 (kg/m
Outdoor Unit
Stop Valve (Liquid Line)
Gas Line
Liquid Line
Multi-Kit
Fig. 5.5 Evacuation and Refrigerant Charge
3
) of each objective room.
3
)
≤
0.3 (kg/m
3
)
≤ Critical Concentration (kg/m
3
)
Manifold Gauge
Vacuum Pump
Cover the flare nut and
unit with thermal insulator.
Indoor Unit
Insulation
Insulation
3
, according to the refrigeration and air conditioning facility
3
) of the room according to the following equation.
3
)
3
)
3
0.3 kg/m
3
, take the following actions.
Nitrogen Tank
(for Nitrogen Blow during Brazing
and Air Tight Test)
Refrigerant Cylinder
(R410A)
Weigher
Indoor Unit
3
, in case of leakage.
13
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