Cfm, Static Pressure, And Power - Altitude And Temperature Corrections; Altitude Correction Factors (°C/Meter); Altitude Correction Factors (°F/Feet) - York SUNLINE 2000 Installation Manual

66396-YIM-C-1004
CFM, STATIC PRESSURE, AND POWER - ALTI-
TUDE 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 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
TABLE 13: ALTITUDE CORRECTION FACTORS (°C/METER)
AIR TEMP
°C
0
4.4 1.060
10 1.039
15.5 1.019
21 1.000
26.6 0.982
32 0.964
38 0.946
TABLE 14: ALTITUDE CORRECTION FACTORS (°F/FEET)
AIR TEMP
°F
0
40 1.060
50 1.039
60 1.019
70 1.000
80 0.982
90 0.964
100 0.946
The examples below will assist in determining the airflow per-
formance 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
14 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 14 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". Use the unit
Unitary Products Group
ALTITUDE (METER)
305 610 914
1.022 0.986 0.950
1.002 0.966 0.931
0.982 0.948 0.913
0.964 0.930 0.896
0.947 0.913 0.880
0.929 0.897 0.864
0.912 0.880 0.848
ALTITUDE (FEET)
1000 2000 3000
1.022 0.986 0.950
1.002 0.966 0.931
0.982 0.948 0.913
0.964 0.930 0.896
0.947 0.913 0.880
0.929 0.897 0.864
0.912 0.880 0.848
order to use the indoor blower tables for high altitude applica-
tions, 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 14 and Figure 13.
1219 1524 1829
0.916 0.882 0.849
0.898 0.864 0.832
0.880 0.848 0.816
0.864 0.832 0.801
0.848 0.817 0.787
0.833 0.802 0.772
0.817 0.787 0.758
4000 5000 6000
0.916 0.882 0.849
0.898 0.864 0.832
0.880 0.848 0.816
0.864 0.832 0.801
0.848 0.817 0.787
0.833 0.802 0.772
0.817 0.787 0.758
blower tables to select the blower speed and the BHP
requirement.
Solution: As in the example above, no temperature informa-
tion is given so 70°F is assumed.
The 1.5" 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". 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
2134 2438 2743
0.818 0.788 0.758
0.802 0.772 0.743
0.787 0.757 0.729
0.772 0.743 0.715
0.758 0.730 0.702
0.744 0.716 0.689
0.730 0.703 0.676
7000 8000 9000
0.818 0.788 0.758
0.802 0.772 0.743
0.787 0.757 0.729
0.772 0.743 0.715
0.758 0.730 0.702
0.744 0.716 0.689
0.730 0.703 0.676
3048
0.729
0.715
0.701
0.688
0.676
0.663
0.651
10000
0.729
0.715
0.701
0.688
0.676
0.663
0.651
21