York ZJ Series Spécifications télécharger pdf (Page 34)

527730-YIM-D-0310

34 Johnson Controls Unitary Products

Figure 27: Altitude/Temperature Correction Factors

The examples below will 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 13

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 15 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

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

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

Table 14: Altitude/Temperature Correction Factors

Air

Temp.

Altitude (Ft.)

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

40 1.060 1.022 0.986 0.950 0.916 0.882 0.849 0.818 0.788 0.758 0.729

50 1.039 1.002 0.966 0.931 0.898 0.864 0.832 0.802 0.772 0.743 0.715

60 1.019 0.982 0.948 0.913 0.880 0.848 0.816 0.787 0.757 0.729 0.701

70 1.000 0.964 0.930 0.896 0.864 0.832 0.801 0.772 0.743 0.715 0.688

80 0.982 0.947 0.913 0.880 0.848 0.817 0.787 0.758 0.730 0.702 0.676

90 0.964 0.929 0.897 0.864 0.833 0.802 0.772 0.744 0.716 0.689 0.663

100 0.946 0.912 0.880 0.848 0.817 0.787 0.758 0.730 0.703 0.676 0.651

0.600

0.650

0.700

0.750

0.800

0.850

0.900

0.950

1.000

1.050

1.100

40 50 60 70 80 90 100

Air Temperature (ºF)

Correction Factor

Sea Level

1000 ft

2000 ft

3000 ft

4000 ft

6000 ft

7000 ft

8000 ft

9000 ft

10000 ft

5000 ft

1 2 ... 29 30 31 32 33 34 35 36 37 38 39 ... 54 55

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