York ZB Series Installation Manual

5808009-YIM-A-0320Johnson Controls Ducted Systems 49Figure 27: Altitude/temperature correction factorsUse the examples below to assist in determining the airflowperformance of the product at altitude.Example 1: What are the corrected CFM, static pressure, andBHP at an elevation of 5,000 ft. if the blower performance datais 1,400 CFM, 0.6 IWC and 0.67 BHP?Solution: At an elevation of 5,000 ft. the indoor blower will stilldeliver 1,400 CFM if the RPM is unchanged. However, you mustuse Table 18 to determine the static pressure and BHP. Weassume an air temperature of 70°F because no temperature datais given, Table 17 shows the correction factor to be 0.832.Corrected static pressure = 0.6 x 0.832 = 0.499 IWCCorrected BHP = 0.67 x 0.832 = 0.56Example 2: A system, located at 5,000 feet of elevation, is todeliver 1,400 CFM at a static pressure of 1.5 in. Use the unitblower tables to select the blower speed and the BHPrequirement.Solution: As in the example above, no temperatureinformation 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 sealevel conditions.Sea level static pressure = 0.6 / .832 = 0.72 in.Enter the blower table at 1,400 sCFM and static pressure of0.72 in. The RPM listed is the same RPM needed at 5,000 ft.Suppose that the corresponding BHP listed in the table is 0.7.This value must be corrected for elevation.BHP at 5,000 ft. = 0.7 x .832 = 0.58Table 17: Altitude/temperature correction factorsAir temp. Altitude (ft.)0 1000 2000 3000 4000 5000 6000 7000 8000 9000 1000040 1.060 1.022 0.986 0.950 0.916 0.882 0.849 0.818 0.788 0.758 0.72950 1.039 1.002 0.966 0.931 0.898 0.864 0.832 0.802 0.772 0.743 0.71560 1.019 0.982 0.948 0.913 0.880 0.848 0.816 0.787 0.757 0.729 0.70170 1.000 0.964 0.930 0.896 0.864 0.832 0.801 0.772 0.743 0.715 0.68880 0.982 0.947 0.913 0.880 0.848 0.817 0.787 0.758 0.730 0.702 0.67690 0.964 0.929 0.897 0.864 0.833 0.802 0.772 0.744 0.716 0.689 0.663100 0.946 0.912 0.880 0.848 0.817 0.787 0.758 0.730 0.703 0.676 0.6510.6000.6500.7000.7500.8000.8500.9000.9501.0001.0501.10040 50 60 70 80 90 100Air Temperature (ºF)Correction Factor Sea Level1000 ft2000 ft3000 ft4000 ft6000 ft7000 ft8000 ft9000 ft10000 ft5000 ft