York SUNLINE MagnaDRY DR180C/E00 Technical Manual

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York SUNLINE MagnaDRY DR180C/E00 Technical Manual Manual pdf 34 page image

036-21539-003-B-030534 Unitary Products GroupCFM, STATIC PRESSURE, AND POWER - ALTI-TUDE AND TEMPERATURE CORRECTIONSThe information below should be used to assist in applicationof product when being applied at altitudes at or exceeding1000 feet above sea level.The air flow rates listed in the standard blower performancetables are based on standard air at sea level. As the altitudeor temperature increases, the density of air decreases. Inorder to use the indoor blower tables for high altitude applica-tions, certain corrections are necessary.A centrifugal fan is a "constant volume" device. This meansthat, if the rpm remains constant, the CFM delivered is thesame regardless of the density of the air. However, since theair at high altitude is less dense, less static pressure will begenerated and less power will be required than a similarapplication at sea level. Air density correction factors areshown in Table 18 and Figure 11.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 performancedata is 6,000 CFM, 1.5 IWC and 4.0 BHP?Solution: At an elevation of 5,000 ft the indoor blower will stilldeliver 6,000 CFM if the rpm is unchanged. However, Table18 must be used to determine the static pressure and BHP.Since no temperature data is given, we will assume an airtemperature of 70°F. Table 18 shows the correction factor tobe 0.832.Corrected static pressure = 1.5 x 0.832 = 1.248 IWCCorrected BHP = 4.0 x 0.832 = 3.328Example 2: A system, located at 5,000 feet of elevation, is todeliver 6,000 CFM at a static pressure of 1.5". Use the unitblower tables to select the blower speed and the BHPrequirement.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 equivalentsea level conditions.Sea level static pressure = 1.5 / .832 = 1.80"Enter the blower table at 6000 sCFM and static pressure of1.8". 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 = 2.66TABLE 18: ALTITUDE CORRECTION FACTORSAIR TEMP ALTITUDE (FEET)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 0.651