Greenheck Fan QEM Ventilation Hood User Manual


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11
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 (C
o
) 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 (C
o
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two discharges will each handle 10,000 cfm.
Plenum Exit Velocity [ft/min]
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2
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3
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2
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System Effect
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4. Now select a fan size from the catalog data based
on the corrected performance. The corrected static
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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
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the option of selecting either model QEM or QEP.
Airstream Temperature Variations
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airstream should be considered: Start-up and normal
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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
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conditions require the same density correction factor
as 13,000 ft. elevation at 70°F, so the fan selection is
still valid.)
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at 9,000 ft. elevation, the air density correction factor
(Table 2A) is 1.14. Divide the cataloged bhp by the
correction factor.
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Now calculate hp during normal operation using the
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The motor should be sized based on the larger of these
two values. So although the normal operation would
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with a 20 hp motor based on the higher hp requirement
at start-up.
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ELEVATION (FEET ABOVE SEA LEVEL)
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000
AIRSTREAM TEMPERATURE (°F)
-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
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
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
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
ELEVATION (METERS ABOVE SEA LEVEL)
0 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3500
AIRSTREAM TEMPERATURE (°C)
-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
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
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
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
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
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
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
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