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Belt driven fan - The unit is equipped with an adjustable motor pulley. The fan speed can be varied
through a given range by adjustment of the pulley. Table 1. shows the setting speed and the variable
speed range. To change the speed, adjust the motor pulley as follows (refer to Fig. 9).
1. Loosen the two bolts on the adjusting bracket for the fan belt tension and loosen the belt by pushing
the motor upward.
2. Loosen the set screw in the movable pulley flange.
3. Turn the movable pulley flange toward the fixed flange to increase the speed, and turn it away from
the fixed flange to decrease the speed. Each turn of the movable flange will increase or decrease the
fan speed by 39 to 46 rpm.
4. Tighten the set screw in the movable pulley, which is positioned over the flat surfaces of the fixed
pulley.
5. Adjust the belt tension (approximately 20 mm deflection with one finger) by pushing the motor
downward and tightening the bolts on the adjusting bracket.
For models RAS-NP4US through RAS-NP8US
■Motor Pulley Dimensions(mm)
Models
a
RAS-NP4US
16
RAS-NP5US
RAS-NP6US
21.5
RAS-NP8US
For Model RAS-NP4US and RAS-NP5US
■Motor Pulley Adjustment
Models
X
PD
RAS-NP4US
RPM 675
PD
RAS-NP5US
RPM 815
PD
RAS-NP6US
RPM 875
PD
RAS-NP8US
RPM 865
RPM ：Fan Speed (rpm)
PD：Pitch Diameter of Pulley (mm)
RPM/Turn：Fan Speed Change per One Turn of Movable Motor Pulley.
FAN SPEED ADJUSTMENT
b
c
d
79
14
5
101
19
6
104.5
Fig. 9-1. Adjustable Motor Pulley
X：Regulation Space of Motor Pulley (mm)
PD：Pitch Diameter of Motor Pulley (mm)
0
1
2
3
69.5
66.3
63.1
60
645
615
585
91.5
88.3
85.1
82
790
760
730
95
91.8
88.6
85.5
845
815
790
95
91.8
88.6
85.5
840
810
780
FAN SPEED ADJUSTMENT
For Model RAS-NP6US and RAS-NP8US
4
5
6
6.5
56.8
53.6
50.5
48.9
550
520
490
475
78.8
75.6
72.5
70.9
705
675
645
635
82.3
79.1
76
74.4
760
730
700
685
82.3
79.1
76
74.4
750
720
695
680
Factory Set Point
RPM/Turn
X
RPM
PD
1.1
640
65.9
3.8
710
79.6
2.3
810
87.9
3
780
85.5
46
43
44
43
16
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