Fan Speed Adjustment - Hitachi RUA-NP4ATS Instruction Manual

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.
For Model RUA-NP4ATS & RUA-NP5ATS
Models
PD
RUA-NP4ATS
RPM 875
PD
RUA-NP5ATS
RPM 955
PD
RUA-NP6ATS
RPM 930
RPM: Fan Speed (rpm)
PD : Pitch Diameter of Motor Pulley (mm)
RPM/Turn: Fan Speed Change per One Turn of Movable Motor Pulley
a b
16 14
Fig. 7-1. Adjustable Motor Pulley
Table 1-1. Fan Speed Adjustment
X：Regulation Space of Motor Pulley (mm)
PD：Pitch Diameter of Motor Pulley (mm)
X 0 1 2
91.5 88.3 85.1
845 815
91.5 88.3 85.1
925 890
95.0 91.8 88.6
900 870
FAN SPEED ADJUSTMENT
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 40 to 45 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.
c
5
For Model RUA-NP6ATS
3 4 5 6
82.0 78.8 75.6 72.5
785 755 725 695
82.0 78.8 75.6 72.5
855 825 790 760
85.5 82.3 79.1 76.0
835 805 775 745
a
21.5 19
Factory Set Point
RPM/Turn
X RPM PD
3.0 785 82.0
4.9 795 76.0
2.3 860 87.9
b c
6
45
49
46
9