Johnson Controls ZL Series Installation Manual page 46

Adjusting the belt tension
The tension on the belt should be adjusted as
shown in Figure 23.
Before you begin:
CAUTION
Procedure for adjusting best tension below:
1. Loosen the three nuts (A and B on side and
C on back) of motor mount slide plate. See
Figure 23.
Figure 23: Belt adjustment
2. Adjust tension by placing a flat heat
screwdriver into the belt tightening slots (1/4
in. X 1/2 in.) in the motor mount slide plate
and applying pressure against the motor
mounting plate. See Figure 23.
Table 21: Altitude/temperature correction factors
Air temp.
0 1000
40 1.060 1.022
50 1.039 1.002
60 1.019 0.982
70 1.000 0.964
80 0.982 0.947
90 0.964 0.929
100 0.946 0.912
46 Installation Manual ZL Series 7.5- 12.5 Ton 60 Hertz R-410A
2000 3000 4000
0.986 0.950 0.916
0.966 0.931 0.898
0.948 0.913 0.880
0.930 0.896 0.864
0.913 0.880 0.848
0.897 0.864 0.833
0.880 0.848 0.817
Johnson Controls Ducted Systems
3. Tighten the three loosened nuts (A, B, and C).
4. Determine the deflection distance from
normal position, use a straight edge from
sheave to sheave as reference line. Use belt
tension checker to apply a perpendicular force
to the belt at the midpoint of the span as
shown. Deflection distance of 4mm (5/32 in.)
is obtained
5. After adjustments are completed re-tighten
nuts (A, B, and C).
Altitude and temperature correction for
cfm, static pressure, and power.
The information below should be used to assist
in application of product when being applied at
altitudes at or exceeding 1,000 ft above sea level.
The air flow rates listed in the standard blower
performance tables are based on standard air at sea
level. As the altitude or temperature increases, the
density of air decreases. In order to use the indoor
blower tables for high altitude applications, certain
corrections are necessary.
A centrifugal fan is a constant volume device. This
means that, if the rpm remains constant, the cfm
delivered is the same regardless of the density of
the air. However, since the air at high altitude is less
dense, less static pressure will be generated and
less power will be required than a similar application
at sea level. Air density correction factors are shown
in Table 21 and Figure 24.
Altitude (ft)
5000 6000 7000
0.882 0.849 0.818
0.864 0.832 0.802
0.848 0.816 0.787
0.832 0.801 0.772
0.817 0.787 0.758
0.802 0.772 0.744
0.787 0.758 0.730
8000 9000 10000
0.788 0.758 0.729
0.772 0.743 0.715
0.757 0.729 0.701
0.743 0.715 0.688
0.730 0.702 0.676
0.716 0.689 0.663
0.703 0.676 0.651