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5121835-TIM-J-1118
Table 17: Altitude/temperature correction factors
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
1.100
1.050
1.000
0.950
0.900
0.850
0.800
0.750
0.700
0.650
0.600
Figure 29: Altitude/temperature correction factors
Use the examples below to assist in determining the airflow
performance of the product at altitude.
Example 1: What are the corrected CFM, static pressure, and
BHP at an elevation of 5,000 ft. if the blower performance data
is 6,000 CFM, 1.5 IWC and 4.0 BHP?
Solution: At an elevation of 5,000 ft. the indoor blower will still
deliver 6,000 CFM if the RPM is unchanged. However, Table 18
must be used to determine the static pressure and BHP. Since
no temperature data is given, we will assume an air temperature
of 70°F. Table 17 shows the correction factor to be 0.832.
Corrected static pressure = 1.5 x 0.832 = 1.248 IWC
Corrected BHP = 4.0 x 0.832 = 3.328
Example 2: A system, located at 5,000 feet of elevation, is to
deliver 6,000 CFM at a static pressure of 1.5 in. Use the unit
40
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
40
50
60
Air Temperature (ºF)
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
70
80
90
blower tables to select the blower speed and the BHP
requirement.
Solution: As in the example above, no temperature
information is given so 70°F is assumed.
The 1.5 in. static pressure given is at an elevation of 5,000 ft.
The first step is to convert this static pressure to equivalent sea
level conditions.
Sea level static pressure = 1.5 / .832 = 1.80"
Enter the blower table at 6000 sCFM and static pressure of
1.8 in. The RPM listed will be the same RPM needed at 5,000
ft.
Suppose that the corresponding BHP listed in the table is 3.2.
This value must be corrected for elevation.
BHP at 5,000 ft. = 3.2 x .832 = 2.66
0.788
0.758
0.772
0.743
0.757
0.729
0.743
0.715
0.730
0.702
0.716
0.689
0.703
0.676
Sea Level
1000 ft
2000 ft
3000 ft
4000 ft
5000 ft
6000 ft
7000 ft
8000 ft
9000 ft
10000 ft
100
Johnson Controls Ducted Systems
0.729
0.715
0.701
0.688
0.676
0.663
0.651
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