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Roof Downblast - Exhaust
Belt Drive
GB-300HP
Performance certified is for installation type A: Free inlet, Free outlet. Power rating (BHP) does not include transmission losses. Performance ratings include the effects
of a birdscreen. The sound ratings shown are loudness values in hemispherical sones at 5 ft. (1.5 m) in a hemispherical free field calculated per AMCA Standard 301.
Values shown are for installation type A: free inlet hemispherical sone levels.
Performance certified is for installation type A: Free inlet, Free outlet. Power rating (BHP) does not include transmission losses. Performance ratings include the effects
of a birdscreen. The sound ratings shown are loudness values in hemispherical sones at 5 ft. (1.5 m) in a hemispherical free field calculated per AMCA Standard 301.
Values shown are for installation type A: free inlet hemispherical sone levels.
1
3
⁄4 (44)
Damper Size = 30 x 30 (762 x 762)
Roof Opening = 32 x 32 (826 x 826)
Shroud Thickness = 0.064 (1.6)
Motor Cover Thickness = 0.051 (1.3)
Curb Cap Thickness = 0.064 (1.6)
^Approximate Unit Weight = 320 lbs. (145 kg)
All dimensions in inches (millimeters). *May be greater depending on
motor. ^Weight shown is largest cataloged Open Drip-Proof motor.
D
O
N
O
T
S
E
L
E
C
T
T
O
T
H
E
L
E
F
T
O
F
T
H
I
S
S
Y
S
T
E
M
C
U
R
V
E
Static Pressure (in. wg)
Static Pressure (Pa)
Volume (cfm x 1000)
3
Volume (m
/hr x 1000)
RPM (Belt)
HP
Density 0.075 lb/ft
3
Density 1.2 kg/m
3
Motor
HP
Fan
RPM
Static Pressure in Inches wg
0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75
300HP
1/2
460
CFM
2912
BHP
0.41
Sones
9.7
495
CFM
3602
BHP
0.53
Sones
10.3
3/4 565
CFM
4662 3600
BHP
0.77 0.76
Sones
11.8 10.4
1 620
CFM
5398 4652 3309
BHP
1.01 1.04 0.94
Sones
13.4 12.3 10.6
1
1
⁄2 710
CFM
6542 5954 5269 4221
BHP
1.48 1.53 1.55 1.47
Sones
17.2 16.0 15.3 13.4
2
748
CFM
7013 6462 5889 5027
BHP
1.71 1.78 1.81 1.78
Sones
18.8 17.5 17.0 15.7
785
CFM
7460 6943 6402 5737 4800
BHP
1.96 2.04 2.08 2.10 2.00
Sones
20 19.1 18.5 17.9 16.2
3
840
CFM
8107 7642 7146 6636 5922 4992
BHP
2.37 2.46 2.52 2.57 2.56 2.43
Sones
23 22 21 21 19.7 18.0
895
CFM
8746 8328 7870 7394 6892 6150 5245
BHP
2.84 2.95 3.03 3.07 3.11 3.08 2.92
Sones
25 24 23 23 23 22 19.8
5
980
CFM
9722 9356 8951 8531 8094 7657 7029 6264 5222
BHP
3.68 3.81 3.90 3.99 4.03 4.08 4.09 3.95 3.69
Sones
32 31 29 28 27 26 25 24 23
1065
CFM
10688 10351 10006 9621 9233 8831 8429 7903 7255 6543
BHP
4.67 4.81 4.94 5.04 5.12 5.17 5.23 5.24 5.17 5.01
Sones
44 42 37 37 36 35 33 31 30 29
MAXIMUM BHP AT A GIVEN RPM = (RPM/613)
3
MAXIMUM RPM = 1065
TIP SPEED (ft/min) = RPM x 7.985
MAXIMUM MOTOR FRAME SIZE = 184T
50
(1270)
8
1
⁄4 (210)
*36
(914)
40
(1016)