Selection Process - Daikin FWW Series Technical Manual

Selection Process

Selection Process
Fan Performance Chart
Example 1 :
The following are the design requirements for FUD30B unit:
Model:
Supply Air Quantity
External Static Pressure
Step 1: From the fan curve (at 4200 CFM),
Standard operating system;
Total Static Pressure
Internal Static Pressure
External Static Pressure
External Static Pressure of 149 Pa did not fulfill the design requirements.
Step 2: Therefore at 4200 CFM and 180 Pa External static pressure,
Total Static Pressure
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
Blower pulley
Motor RPM
In order to obtain 800 RPM, we recalculate the new blower pulley as:
(while maintaining the motor pulley)
Db
The nearest pulley size will be a diameter of 140mm
Recheck, with Db = 140mm
Blower pulley
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
configuration:
V-belt length, L
We thus can use a belt with a length of 1030mm
where,
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 sufficient to drive the blower with the smaller 140mm pulley.
Summary:
i) Fan motor kW
ii) Blower pulley diameter
iii) V-belt size
FUD30B
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=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
C =
Db =
Dm =
=
=
=
4200 CFM
180 Pa
320 Pa
171
Pa
149 Pa
171 + 180 Pa
351 Pa
80 mm
160 mm
1405
80 x (1405/800)
140.5 mm
1405 x (80/140)
803
2C + 1.57 (Db + Dm)
(2 x 340) + 1.57 (80 + 140)
1025.4mm
distance between the centres of the two pulleys
diameter of blower pulley
diameter of motor pulley
1.5 kW
140 mm
1030 mm
67