Acson SB75BW User Manual

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Selection Process
Selection Process
Fan Performance Chart
Example 1 :
The following are the design requirements for ADB125W unit:
Model: ADB125BW
Supply Air Quantity = 4200 CFM
External Static Pressure = 180 Pa
Step 1: From the fan curve (at 4200 CFM),
Standard operating system;
Total Static Pressure = 320 Pa
Internal Static Pressure = 171 Pa
External Static Pressure = 149 Pa
External Static Pressure of 149 Pa did not fulll the design requirements.
Step 2: Therefore at 4200 CFM and 180 Pa External static pressure,
Total Static Pressure = 171 + 180 Pa
= 351 Pa
Step 3: From the fan curve, the design requirement calls for RPM about 800, whereas the unit can only deliver
RPM about 760 under the same CFM. Therefore, it is necessary to resize the pulley sizes.
From the table:
Motor pulley = 80 mm
Blower pulley = 160 mm
Motor RPM = 1405
In order to obtain 800 RPM, we recalculate the new blower pulley as:
(while maintaining the motor pulley)
Db = 80 x (1405/800)
= 140.5 mm
The nearest pulley size will be a diameter of 140mm
Recheck, with Db = 140mm
Blower pulley = 1405 x (80/140)
= 803
We thus need to change the blower pulley from 160mm to 140mm in order to obtain the higher operating
static pressure.
Step 4: When the pulley is changed, the V-belt length must be rechecked. We have for horizontal air throw
conguration:
V-belt length, L = 2C + 1.57 (Db + Dm)
= (2 x 340) + 1.57 (80 + 140)
= 1025.4mm
We thus can use a belt with a length of 1030mm
where, C = distance between the centres of the two pulleys
Db = diameter of blower pulley
Dm = diameter of motor pulley
Step 5: From the fan curve, we can also notice that the motor power input has increased. At the new operating
point, the power is approximately 1.25 kW.
By applying a safety factor of 1.2 to account for losses, we calculate that the motor power input requirement
should be = 1.25 x 1.2 = 1.5 kW
Thus, the existing motor is still sufcient to drive the blower with the smaller 140mm pulley.
Summary:
i) Fan motor kW = 1.5 kW
ii) Blower pulley diameter = 140 mm
iii) V-belt size = 1030 mm

Acson SB75BW Specifications

General

Brand	Acson
Model	SB75BW
Category	Fan
Language	English