Altitude And Temperature Corrections; Altitude Correction Factors - York ECO HFC-410A User Manual

Altitude and Temperature Corrections

The information below should be used to assist in
application of product when being applied at altitudes
at or exceeding 1000 feet above sea level.
The airfl ow rates listed in the standard blower perfor-
mance 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.
TABLE 7 – ALTITUDE-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
The examples below will assist in determining the airfl ow
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 7 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 7 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
JOHNSON CONTROLS
Altitude (feet)
2000 3000 4000
0.986 0.95 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
0.88 0.848 0.817
A centrifugal fan is a "constant-volume" device. This
means that if the RPM remains constant, the CFM de-
livered 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 7 and
Figure 2.
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
Example 2: A system, located at 5,000 feet of elevation,
is to deliver 6,000 CFM at a static pressure of 1.5". Use
the unit 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" static pressure given is at an elevation of
5,000 ft. The fi rst step is to convert this static pressure
to equivalent sea-level conditions.
Sea-level static pressure = 1.5 / 0.832 = 1.80"
Enter the blower table at 6000 sCFM and static pressure
of 1.8". The RPM listed will be the same RPM needed
at 5,000 ft.
Suppose that the corresponding BHP listed in the blower
table is 3.2.
This value must be corrected for elevation.
BHP at 5,000 ft = 3.2 x .832 = 2.66
FORM 100.50-EG5 (108)
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
0.73 0.702 0.676
0.716 0.689 0.663
0.703 0.676 0.651
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