Specifications

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The following are the design requirements for MRT100A unit:
Model: MRT100A
Supply Air Quantity=3800 CFM
External Static Pressure = 150 Pa
Step 1:From the blower curve (at 3800 CFM),
Standard operating system;
Internal Static Pressure = 160 Pa
Step 2:Therefore at 3800 CFM and 150 Pa external static pressure,
To tal Static Pressure = 150 + 160 Pa
= 310 Pa
Step 3:From the blower curve, the design requirement calls for RPM about 1200 RPM.
From the table:
Motor pulley =106 mm
Blower pulley = 125 mm
Motor RPM= 1
420
In order to obtain 1
380 RPM, we calculate the new blower pulley as:
(while maintaining the motor pulley)
Db =106 x (1420/1380)
= 109.1 mm
Let us take close approximation of 1
10 mm diameter pulley size
Recheck, with Db = 110 mm
Blow pulley = 1420 x (1
06/110)
= 1368.4. RPM
We thus need to change the blower pulley from 125 mm to 110 mm in order to obtain the higher operating
static pressure.
Step 3:When the pulley is changed, the V-belt length must be rechecked. We have for horizontal air throw
configuration:
V-belt length, L = 2C + 1.57 (Db + Dm)
=(2 x 174) + 1.57(110+ 106)
= 687.12
We thus can use a belt with a length of 687
mm.
where, C = distance between the centres of the two pulleys
Db =
diameter of blower pulley
Dm = diameter of motor pulley
Step 4:From the blower curve, we can also notice that the motor power input has maintained within the current
operating range of the standard unit's motor.
Summary:
i) Fan motor kW = 2.2 kW
ii) Blower pulley diameter = 110 mm
iii) V-belt siz = 687 mm
Note: Factory supplied rooftop is only with standard drive package.
All other changes are only given as example and need to be field supply.
Selection Process
Drive Package