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ROOF CURB MOUNTING
1. Factory Supplied Roof Curbs
Roof curbs are Model GKD, which are shipped in a
knockdown kit and require field assembly (by
others). Assembly instructions are included with
the curb.
2. Cut Roof Opening and Locate Curb
Layout the unit roof opening such that the supply
discharge & exhaust inlet of the unit will line up
with the corresponding ductwork (refer to
Recommended Roof Openings on page 3). Be
sure to allow for the recommended service
clearances. Keep the supply inlet of the unit away
from any other exhaust fans.
3. Install Curb
Locate curb over roof opening and fasten in place.
Check that the diagonal dimensions are within
±1/8 inch of each other and adjust as necessary.
Shim as required to level. Lower unit onto curb by
following the LIFTING instructions on page 3 of
this manual. Note,
roof curbs fit inside
the unit base.
4. Install Duct Work
Installation of all
ducts should be
done in accordance
with SMACNA and
AMCA guidelines.
DUCT WORK CONNECTIONS
Examples of good and poor fan-to-duct connections are shown below (See FIGURE 4). Airflow out of the fan
should be directed straight or curve the same direction as the fan wheel rotates. Poor duct installation will result
in low airflow and other system effects.
Length of Straight Duct
GOOD
4
TABLE 3
Curb Outside Dimensions
Model
L
ERH-20
73
ERH-45
80.75
ERH-55
94
ERH-90
106.25
Dimensions shown are in inches.
Recommended Discharge
TABLE 4
Duct Size and Length
ERH
Model
20
45
55
90
Dimensions shown are in inches.
W
51
60.63
Roof curb details, including duct
71.5
location dimensions, are available
90.75
on ERH roof curb submittals.
FIGURE 4
ERH
Straight
Duct
Blower
Duct
Size
Size
Length
10
14 x 14
40
12
20 x 20
48
15
28 x 28
60
18
32 x 32
72
W
POOR
L
FIGURE 3
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