Orion System OE742-XX-VAVZ - Manual (Page 25)

Form: ORION-OE519-RectDmpr-Sub-01B.doc
Page 2 of 2
Using the maximum acceptable velocity for a
branch duct (typically 1000-1500 FPM for
minimal noise), find the smallest damper that
will deliver the required CFM as determined by
the load program.
Locate the required CFM on the Rectangular
Damper Selection Data table below. This table
is based on an airflow velocity of 1000 FPM
across the damper.
Rectangular Damper Selection Data
Damper
Height
“B”
8” 10” 12” 14” 16” 18” 20” 22” 24” 26” 28” 30” 32” 34” 36”
Damper
Width
“A”
Airflow Data with Full Open Damper
CFM @ 1000 FPM Velocity
( ∆ P
S
- inches W.C. @ 1000 FPM Velocity)
8” 410
(0.16)
530
(0.10)
640
(0.07)
740
(0.05)
850
(0.04)
970
(0.03)
1080
(0.03)
1190
(0.02)
1300
(0.02)
1410
(0.02)
1520
(0.01)
1630
(0.02)
1740
(0.01)
1850
(0.01)
1970
(0.01)
10” 510
(0.10)
590
(0.07)
690
(0.05)
800
(0.03)
910
(0.03)
1030
(0.02)
1150
(0.02)
1260
(0.01)
1380
(0.01)
1500
(0.01)
1610
(0.01)
1730
(0.01)
1840
(0.01)
2000
(0.01)
2080
(0.01)
12” 560
(0.07)
650
(0.05)
730
(0.03)
850
(0.02)
970
(0.02)
1090
(0.01)
1210
(0.01)
1330
(0.01)
1460
(0.01)
1580
(0.01)
1700
(0.01)
1820
(0.01)
1940
(-)
2060
(-)
2190
(-)
14” 660
(0.05)
770
(0.03)
880
(0.02)
1030
(0.02)
1180
(0.01)
1330
(0.01)
1480
(0.01)
1630
(0.01)
1760
(0.01)
1910
(0.01)
2060
(-)
2210
(-)
2360
(-)
2510
(-)
2640
(-)
16” 750
(0.04)
890
(0.03)
1030
(0.02)
1200
(0.01)
1370
(0.01)
1540
(0.01)
1710
(0.01)
1880
(0.01)
2060
(-)
2230
(-)
2400
(-)
2570
(-)
2740
(-)
2910
(-)
3090
(-)
18” 770
(0.03)
980
(0.03)
1180
(0.01)
1380
(0.01)
1580
(0.01)
1780
(0.01)
1980
(0.01)
2180
(-)
2350
(-)
2550
(-)
2750
(-)
2950
(-)
3150
(-)
3350
(-)
3540
(-)
20” 850
(0.03)
1090
(0.02)
1330
(0.01)
1550
(0.01)
1770
(0.01)
1990
(0.01)
2210
(-)
2430
(-)
2650
(-)
2870
(-)
3090
(-)
3310
(-)
3530
(-)
3750
(-)
3990
(-)
22” 930
(0.02)
1210
(0.01)
1480
(0.01)
1730
(0.01)
1980
(0.01)
2230
(-)
2480
(-)
2730
(-)
2950
(-)
3200
(-)
3450
(-)
3700
(-)
3950
(-)
4200
(-)
4440
(-)
24” 950
(0.02)
1290
(0.01)
1630
(0.01)
1900
(0.01)
2170
(-)
2440
(-)
2710
(-)
2980
(-)
3250
(-)
3520
(-)
3790
(-)
4060
(-)
4330
(-)
4600
(-)
4880
(-)
26” 990
(0.02)
1390
(0.01)
1780
(0.01)
2080
(0.01)
2380
(-)
2680
(-)
2980
(-)
3280
(-)
3550
(-)
3850
(-)
4150
(-)
4450
(-)
4750
(-)
NA NA
28” 1070
(0.01)
1500
(0.01)
1930
(0.01)
2250
(-)
2570
(-)
2890
(-)
3210
(-)
3530
(-)
3850
(-)
4170
(-)
4500
(-)
4820
(-)
NA NA NA
30” 1020
(0.01)
1550
(0.01)
2080
(0.01)
2430
(-)
2780
(-)
3130
(-)
3480
(-)
3830
(-)
4150
(-)
4500
(-)
4850
(-)
NA NA NA NA
32” 1090
(0.01)
1660
(0.01)
2230
(-)
2600
(-)
2970
(-)
3340
(-)
3710
(-)
4080
(-)
4450
(-)
4820
(-)
NA NA NA NA NA
34” 1150
(0.01)
1770
(0.01)
2380
(-)
2780
(-)
3180
(-)
3580
(-)
3980
(-)
4370
(-)
4750
(-)
NA NA NA NA NA NA
36” 1060
(0.01)
1790
(0.01)
2520
(-)
2670
(-)
3090
(-)
3510
(-)
3930
(-)
4350
(-)
5040
(-)
NA NA NA NA NA NA
WattMaster reserves the right to change specifications without notice
Notes:
1. The table above is calculated based on 1000 FPM velocity across the full open damper. For other velocities use the
following multipliers to obtain the correct CFM: 500 FPM = 0.5, 1500 FPM = 1.5, 2000 FPM = 2.0. It is recommended
the damper velocity does not exceed 1500 FPM for quiet operation.
2. Pressure drop ( ∆ P
S
) is based on 1000 FPM Velocity. Any pressure drop less than 0.01” W.C. is shown as (-).
This is the recommended velocity for quiet operation and nor-
mal pressure drop through the damper. When space consid-
erations or design criteria dictate, dampers may be selected for
other face velocities by using the multipliers listed in the notes
associated with the table. Move across the table and find the
damper selection, which will provide the required CFM and fit
within the ceiling area where the damper will be located. Many
size selections are possible for a given CFM. Pressure drop
across the damper is shown in parenthesis below the CFM.
OE519 - Rectangular Damper