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
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
8. The attentive matters in installation of air suction and discharging duct
Recommend to use anti-frost and sound-absorbing
duct. (locally bought)
The duct installation work should be finished before the
fitment of ceiling.
The duct must be heat insulated.
The specific air-discharging outlet should be installed at
the place where the airflow can be reasonably distributed.
The surface should leave a checking meatus for checking
and maintenance.
9. The examples of improper installation
Do not use air in duct and take the ceiling inner side instead. The result is because of the irregular
outer air mass, strong wind and sunshine, the humidity is increased.
There may be water drop on the outside of duct. For cement and other new constructions, even if not
taking ceiling inner side as duct, the humidity will also be so high. At this time, use glass fiber
to perform heat preservation to the whole. (use iron net to bind the glass fiber)
Affected by the capacity of air discharging fan, the strong wind in the outer duct and wind direction,
when unit air sending volume exceeds the limit, the discharged water of heat exchanger will overflow,
leading to water leakage.
Air
Air
Duct
Special air discharging outlet
Use screw bolt to fix
Maybe exceeding the unit operation limit (for example: when indoor dry bulb temperature is 35degree,
web bulb temperature is 24degree), it may lead to overload of compressor.
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Model: AD182ALERA AD362AHERA
Commercial Air Conditioner
22
