16
The calculation of duct resistance (the simple calculation is as follow table)
Straight part
Bend part
Air out part
Static pressure box
Air inlet grille (with air filter)
Calculate as per 1m length 1Pa, 1Pa/m
Each bend takes as a3~4m long straight duct
Calculate as 25Pa
Calculate as 50Pa/each
Calculate as 40Pa/each
Good example
Bad example
Bad example
The length difference among every duct is limited below 2:1.
Reduce the length of duct as possible as can.
Reduce the amount of bend as possible as can.
Use heat insulation material to bind and seal the part connecting main unit and the flare part of air
discharging duct. Perform duct installation work, before the fitment of ceiling.
7. Calculation method of the dimension of the simple quadrate air duct
Presuming the unit length friction impedance of the duct is 1Pa/m, when the dimension of one side of
the air duct is fixed as 250mm, as shown below:
Note:1Pa/m=0.1mmAg/m
The chosen chart of simple duct
m
3
/h(m
3
/n)
100
200
300
400
500
600(10)
800
1,000
1,200(20)
250 x 60
(mmxmm)
250 x 90
250 x 120
250 x 140
250 x 170
250 x 190
250 x 230
250 x 270
250 x 310
Shape
Item
Air volume
Square duct
Dimension
m
3
/h(m
3
/n)
1,400
1,600
1,800(30)
2000
2400
3,000(50)
3,500
4,000
4,500
5,000
5,500
6,000(100)
(mmxmm)
250 x 350
250 x 390
250 x 430
250 x 470
250 x 560
250 x 650
250 x 740
250 x 830
250 x 920
250 x 1000
250 x 1090
250 x 1180
Shape
Item
Air volume
Square duct
Dimension
Static pressure box
Air conditioner
Equipped with
air filter (bought)
B
A
A
A
B
A
300m
3
/h
(5m
3
/min)
Duct(mmxmm)
1200m
3
/h
(20m
3
/min)
250x310
250x120
Air volume
Installation Manual For Indoor Unit
