System

Considerations

3.System effects for plenum discharges must also be calculated and added to the design pressure. In a properly designed plenum (see Duct System Effect

section), the system effect coefficient (Co) depends on the orientation of the discharge relative to the fan and duct connection (if any). For air plenums with multiple discharges, calculate the system effect by using the highest loss coefficient for all discharges. In this example, the discharges are ducted so the

highest loss will be axial (Co "TTVNFUIBUUIF two discharges will each handle 10,000 cfm.

Plenum Exit Velocity [ft/min]

7PMVNF<GU3NJO>0VUMFU"SFB<GU2>

<GU3NJO> JOYJO<JO2GU2>

<GUNJO>

System Effect

 $oY%FOTJUZ<MCGU3> Y

  &YJU7FMPDJUZ<GUNJO> 2

YY  2

4.Now select a fan size from the catalog data based on the corrected performance. The corrected static

QSFTTVSF PG  JO XH QMVT UIF TZTUFN FGGFDU PG JO XH NFBOT UIF GBO TIPVME CF TFMFDUFE GPS

20,000 cfm at 4.0 in. wg. A size 33 plenum will meet this performance at 1290 frpm using 17.9 bhp. (Note: The bhp does not include drive losses. Consult AMCA Publication 203-90 for help in estimating drive

MPTTFT  #BTFE PO UIF SFRVJSFE GSQN UIF VTFS IBT the option of selecting either model QEM or QEP.

 

 

 

 

 

ELEVATION (FEET ABOVE SEA LEVEL)

 

 

 

 

 

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

 

-50

0.77

0.80

0.83

0.86

0.89

0.93

0.96

1.00

1.03

1.07

1.11

1.15

1.20

1.24

 

-25

0.82

0.85

0.88

0.92

0.95

0.98

1.02

1.06

1.10

1.14

1.18

1.22

1.27

1.32

 

0

0.87

0.90

0.93

0.97

1.00

1.04

1.08

1.12

1.16

1.20

1.25

1.29

1.34

1.39

 

50

0.96

1.00

1.03

1.07

1.11

1.15

1.20

1.24

1.29

1.33

1.38

1.44

1.49

1.54

 

70

1.00

1.04

1.08

1.12

1.16

1.20

1.24

1.29

1.34

1.39

1.44

1.49

1.55

1.60

(°F)

100

1.06

1.10

1.14

1.18

1.22

1.27

1.31

1.36

1.41

1.47

1.52

1.58

1.63

1.69

150

1.15

1.19

1.24

1.28

1.33

1.38

1.43

1.48

1.54

1.60

1.66

1.72

1.78

1.85

TEMPERATURE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

200

1.25

1.29

1.34

1.39

1.44

1.49

1.55

1.61

1.67

1.73

1.79

1.86

1.93

2.00

 

 

250

1.34

1.39

1.44

1.49

1.55

1.61

1.67

1.73

1.79

1.86

1.93

2.00

2.07

2.15

 

300

1.43

1.49

1.54

1.60

1.66

1.72

1.78

1.85

1.92

1.99

2.06

2.14

2.22

2.30

 

350

1.53

1.58

1.64

1.70

1.77

1.83

1.90

1.97

2.04

2.12

2.20

2.28

2.36

2.45

 

400

1.62

1.68

1.74

1.81

1.88

1.95

2.02

2.09

2.17

2.25

2.33

2.42

2.51

2.60

 

450

1.72

1.78

1.85

1.91

1.99

2.06

2.14

2.21

2.30

2.38

2.47

2.56

2.66

2.75

AIRSTREAM

500

1.81

1.88

1.95

2.02

2.09

2.17

2.25

2.34

2.42

2.51

2.60

2.70

2.80

2.90

550

1.91

1.98

2.05

2.13

2.20

2.29

2.37

2.46

2.55

2.64

2.74

2.84

2.95

3.06

 

 

600

2.00

2.07

2.15

2.23

2.31

2.40

2.49

2.58

2.67

2.77

2.88

2.98

3.09

3.21

 

650

2.09

2.17

2.25

2.34

2.42

2.51

2.60

2.70

2.80

2.90

3.01

3.12

3.24

3.36

 

700

2.19

2.27

2.35

2.44

2.53

2.62

2.72

2.82

2.93

3.04

3.15

3.26

3.38

3.51

 

750

2.28

2.37

2.46

2.55

2.64

2.74

2.84

2.94

3.05

3.17

3.28

3.40

3.53

3.66

 

800

2.38

2.47

2.56

2.65

2.75

2.85

2.96

3.07

3.18

3.30

3.42

3.55

3.68

3.81

 

850

2.47

2.56

2.66

2.76

2.86

2.96

3.07

3.19

3.31

3.43

3.55

3.69

3.82

3.96

 

900

2.57

2.66

2.76

2.86

2.97

3.08

3.19

3.31

3.43

3.56

3.69

3.83

3.97

4.12

 

950

2.66

2.76

2.86

2.97

3.08

3.19

3.31

3.43

3.56

3.69

3.83

3.97

4.11

4.27

 

1000

2.75

2.86

2.96

3.07

3.19

3.30

3.43

3.55

3.68

3.82

3.96

4.11

4.26

4.42

5"#-&" %FOTJUZ$PSSFDUJPO'BDUPST

*NQFSJBM6OJUT



Airstream Temperature Variations

8IFO B GBO JT TFMFDUFE UXP UFNQFSBUVSFT JO UIF airstream should be considered: Start-up and normal PQFSBUJPO 8IJMF UIF IQ SFRVJSFE JT SFEVDFE BU IJHIFS temperatures, the motor must be sized based the lowest temperature that could be present in the airstream (when air density is at its maximum value).

Reconsider the example assuming that the fan was operating at 9,000 ft. elevation with a start-up BJSTUSFBNUFNQFSBUVSFPG¡'BOEBOPSNBMPQFSBUJOH UFNQFSBUVSFPG¡' /PUFUIFOFXOPSNBMPQFSBUJOH conditions require the same density correction factor as 13,000 ft. elevation at 70°F, so the fan selection is still valid.)

'JSTUDBMDVMBUFIQBUUIFTUBSUVQDPOEJUJPO'PS¡' at 9,000 ft. elevation, the air density correction factor (Table 2A) is 1.14. Divide the cataloged bhp by the correction factor.

 ŸCIQBUTUBSUVQ

Now calculate hp during normal operation using the TBNFQSPDFEVSFCVUGPS¡'BUGUFMFWBUJPO

ŸCIQEVSJOHOPSNBMPQFSBUJPO

The motor should be sized based on the larger of these two values. So although the normal operation would POMZSFRVJSFBIQNPUPSUIFGBOTIPVMECFTFMFDUFE with a 20 hp motor based on the higher hp requirement at start-up.

 

 

 

 

ELEVATION (METERS ABOVE SEA LEVEL)

 

 

 

 

0

250

500

750

1000

1250

1500

1750

2000

2250

2500

2750

3000

3500

 

-50

0.76

0.78

0.81

0.83

0.85

0.88

0.91

0.93

0.96

0.99

1.02

1.05

1.08

1.15

 

-25

0.84

0.87

0.90

0.92

0.95

0.98

1.01

1.04

1.07

1.10

1.14

1.17

1.21

1.28

 

0

0.93

0.96

0.99

1.02

1.05

1.08

1.11

1.14

1.18

1.21

1.25

1.29

1.33

1.41

 

21

1.00

1.03

1.06

1.09

1.13

1.16

1.20

1.23

1.27

1.31

1.35

1.39

1.43

1.52

 

50

1.10

1.13

1.17

1.20

1.24

1.27

1.31

1.35

1.39

1.44

1.48

1.52

1.57

1.67

(°C)

75

1.18

1.22

1.26

1.29

1.33

1.37

1.41

1.46

1.50

1.55

1.59

1.64

1.69

1.80

100

1.27

1.31

1.35

1.39

1.43

1.47

1.52

1.56

1.61

1.66

1.71

1.76

1.81

1.92

TEMPERATURE

125

1.35

1.39

1.44

1.48

1.52

1.57

1.62

1.67

1.72

1.77

1.82

1.88

1.93

2.05

 

 

150

1.44

1.48

1.53

1.57

1.62

1.67

1.72

1.77

1.82

1.88

1.94

2.00

2.06

2.18

 

175

1.52

1.57

1.62

1.67

1.72

1.77

1.82

1.88

1.93

1.99

2.05

2.11

2.18

2.31

 

200

1.61

1.66

1.71

1.76

1.81

1.87

1.92

1.98

2.04

2.10

2.17

2.23

2.30

2.44

 

225

1.69

1.74

1.80

1.85

1.91

1.96

2.02

2.09

2.15

2.21

2.28

2.35

2.42

2.57

 

250

1.78

1.83

1.89

1.94

2.00

2.06

2.13

2.19

2.26

2.32

2.39

2.47

2.54

2.70

AIRSTREAM

275

1.86

1.92

1.98

2.04

2.10

2.16

2.23

2.29

2.36

2.44

2.51

2.58

2.66

2.83

400

2.29

2.36

2.43

2.50

2.58

2.65

2.73

2.82

2.90

2.99

3.08

3.17

3.27

3.47

 

300

1.95

2.01

2.07

2.13

2.19

2.26

2.33

2.40

2.47

2.55

2.62

2.70

2.78

2.96

 

325

2.03

2.09

2.16

2.22

2.29

2.36

2.43

2.50

2.58

2.66

2.74

2.82

2.91

3.08

 

350

2.12

2.18

2.25

2.31

2.38

2.46

2.53

2.61

2.69

2.77

2.85

2.94

3.03

3.21

 

375

2.20

2.27

2.34

2.41

2.48

2.56

2.63

2.71

2.79

2.88

2.97

3.06

3.15

3.34

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

425

2.37

2.44

2.52

2.59

2.67

2.75

2.84

2.92

3.01

3.10

3.20

3.29

3.39

3.60

 

450

2.46

2.53

2.61

2.69

2.77

2.85

2.94

3.03

3.12

3.21

3.31

3.41

3.51

3.73

 

475

2.54

2.62

2.70

2.78

2.86

2.95

3.04

3.13

3.23

3.32

3.42

3.53

3.63

3.86

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

500

2.63

2.71

2.79

2.87

2.96

3.05

3.14

3.24

3.33

3.43

3.54

3.65

3.76

3.99

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

550

2.80

2.88

2.97

3.06

3.15

3.25

3.34

3.44

3.55

3.66

3.77

3.88

4.00

4.24

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5"#-&# %FOTJUZ$PSSFDUJPO'BDUPST

.FUSJD6OJUT

11

Page 10 Page 12
Page 11
Image 11
Greenheck Fan QEM, QEP manual Airstream Temperature Variations, Plenum Exit Velocity ft/min
Page 10 Page 12
Top Page Image Contents