Mitsubishi Electric PUMY-P36NKMU4 Technical & Service Manual page 146

10-2. PRECAUTIONS AGAINST REFRIGERANT LEAKAGE
10-2-1. Introduction
R410A refrigerant of this air conditioner is non-toxic and non-flammable but leaking of large amount from an indoor unit into
the room where the unit is installed may be deleterious. To prevent possible injury, the rooms should be large enough to keep the
R410A concentration specified by ISO 5149-1 as follows.
Maximum concentration
Maximum refrigerant concentration of R410A of a room is
0.44kg/m accordance with ISO 5149-1.
3
To facilitate calculation, the maximum concentration is
expressed in units of kg/m
3
Maximum concentration of R410A: 0.027 lbs/ft
(ISO 5149-1)
10-2-2. Confirming procedure of R410A concentration
Follow (1) to (3) to confirm the R410A concentration and take appropriate treatment, if necessary.
(1) Calculate total refrigerant amount by each refrigerant system. Total refrigerant amount is precharged
refrigerant at ex-factory plus additional charged amount at field installation.
Note:
When the air conditioning system consists of several independent refrigerant system, figure out the total refrigerant
amount by each independent refrigerant system.
(2) Calculate room volumes (m
The part with represents the room with the smallest volume.
(a) Situation in which there are no partitions
Indoor unit
(c) If the smallest room has mechanical ventilation apparatus that is linked to a household gas detection and alarm
device, the calculations should be performed for the second smallest room.
Ventilation apparatus
The smallest The second
room smallest room
(3) Use the results of calculations (1) and (2) to calculate the refrigerant concentration:
Total refrigerant in the refrigerating unit (lbs [kg])
The smallest room in which an indoor
m
unit has been installed (ft³ [ 3 ])
OCH811A
[lbs/ft ] (kg [lbs] of R410A per m
3
[0.44
3 kg
) and find the room with the smallest volume
3
Outdoor unit
Outdoor unit
Indoor unit
Maximum concentration(lbs/ft³ [kg/
Maximum concentration of R410A:0.027 lbs/ft³
[0.44kg/m ]
3
Outdoor unit
Direction
of refrigerant flow
[ft ])
3 3
/ ]
m
3
Indoor unit
All refrigerant of this system will leak out to this
room if there is leakage at this indoor unit.
(b) There are partitions, but there are openings that allow
the effective mixing of air.
Indoor unit
Opening
If the calculation results do not exceed the maximum con-
m
3 ])
centration, perform the same calculations for the larger
second and third room, etc., until it has been determined
that nowhere the maximum concentration will be exceeded.
146
Branching header
Outdoor unit
(Situation in which there
are no door openings or
in which there are open-
ings above and blow
doors that occupy at
Wall
least 0.15% of the floor
area)