18
Checking of limit density
Density limit is determined on the basis of the size of a room
using an indoor unit of minimum capacity. For instance, when
an indoor unit is used in a room (floor area 161 ft.
2
× ceiling
height 8.8 ft. = room volume 1417 ft.
3
), the graph at right
shows that the minimum room volume should be 2455 ft.
3
(floor area 279 ft.
2
) for refrigerant of 418 oz.
<Determination by calculation>
Overall refrigerant charge amount for the air conditioner: oz
(Minimum room volume for indoor unit: ft.
3
)
=
418 (oz)
= 0.29 (oz/ft.
3
) < 0.3 (oz/ft.
3
)
1417 (ft.
3
)
Therefore, openings such as louvers are not required for this
room.
ft.
ft.
0.3 oz/ft.
0.3 oz/ft.
● Obtain liquid tubing size from Tables 1-9, 10, 11, 12 and 15.
Main tubing
LA = ø5/8 (ft.) (Total capacity of indoor unit is 179,400 BTU/h) The longest tubing length in this example
LB = ø1/2 (ft.) (Total capacity of indoor unit is 131,600 BTU/h) (LA = 131 ft.)
LC = ø3/8 (ft.) (Total capacity of indoor unit is 83,800 BTU/h)
Distribution joint tubing
Outdoor side A: ø3/8 (ft.) B: ø3/8 (ft.) (from outdoor unit connection tubing)
Indoor side 1: ø3/8 (ft.) 2: ø3/8 (ft.) 3: ø3/8 (ft.) 4: ø3/8 (ft.) (from indoor unit connection tubing)
● Obtain charge amount for each tubing size
Note that the charge amounts per 1 meter are different for each liquid tubing size.
ø5/8 (ft.) → LA : 131 ft. × 1.99 oz/ft. = 261 oz
ø1/2 (ft.) → LB : 16 ft. × 1.38 oz/ft. = 22 oz
ø3/8 (ft.) → LC + A – B + 1 – 4 : 225 ft. × 0.602 oz/ft. = 135 oz
Total 418 oz
Additional refrigerant charge amount is 418 oz.
Be sure to check the limit density for
the room in which the indoor unit is
installed.
