Belt Tension; Altitude And Temperature Correction For Cfm, Static Pressure And Power - York International ZQ Series Installation Manual

Belt Tension

The tension on the belt should be adjusted as shown in Figure 23.
Figure 23: Belt Adjustment
CAUTION
Procedure for adjusting belt tension:
1. Loosen the three nuts (A and B on side and C on
back) of motor mount slide plate.
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.
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 4 mm (5/32 in.)
is obtained.
5. After adjustments are completed re-tighten nuts (A,
B, and C).
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
44 INSTALLATION MANUAL ZQ SERIES 3 - 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
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 1000 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