7
FAN SPEED ADJUSTMENT
4. FAN SPEED ADJUSTMENT
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. 7).
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 45 rpm for (models
RUA-13AT3S and RUA-15AT3S) and 32 rpm
for (models RUA-20AT3S and RUA-30AT3S).
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 RUA-13AT3S and RUA-15AT3S For Models RUA-20AT3S through RUA-30AT3S
Fig. 7. Adjustable Motor Pulley
Table 1. Fan Speed Adjustment
Model
Regulation Space X of Motor Pulley (mm)
Factory Set Point
RPM/Turn**
17
18
19
20
21
22
23
24
x
RPM PD*
RUA-13AT3S
RPM 1,120 1,090 1,060 1,025
995
960
930
900
23
930
93
45
PD*
112
109
106
103
99
96
93
90
RUA-15AT3S
RPM 1,120 1,090 1,060 1,025
995
960
930
900
21.5
970
99
45
PD*
112
109
106
103
99
96
93
90
Model
Regulation Space X of Motor Pulley (mm)
Factory Set Point
RPM/Turn**
0
1
2
3
4
5
6
7
8
X
RPM PD*
RUA-20AT3S
RPM 1,000 980 960
935
910 890 870 850 830
8
830
125
43
PD*
150
147 144 140.5 137 134 131 128 125
RUA-30AT3S
RPM 1,000 980 960
935
910 890 870 850 830
4
910
137
43
PD*
150
147 144 140.5 137 134 131 128 125
RPM: Fan Speed (RPM)
PD* : Pitch Diameter of Motor Pulley (mm)
RPM/Turn**: Fan Speed Change per One Turn of Movable Motor Pulley Flange (RPM per Turn)
