Roof Curb Mounting
Roof curb details including duct location dimensions,
are available on ERV Roof Curb Assembly Instructions.
Rooftop units require curbs to be mounted first. The
duct connections must be located so they will be clear
of structural members of the building.
1. Factory Supplied Roof Curbs: Roof curbs are
Model GKD. The GKD ships in a knockdown kit
(includes duct adapter) and requires field assembly
(by others). Assembly instructions are included with
the GKD curbs.
2. Install Curb: Locate curb over roof opening and
fasten in place. (Refer to Recommended Roof
Openings & Weights). Check that the diagonal
dimensions are within ±1/8 inch of each other and
adjust as necessary. For proper unit operation, it
is important that the installation be level. Shim as
required to level.
3. Install Ductwork: Installation of all ducts should
be done in accordance with SMACNA and AMCA
guidelines. Duct adapter provided to support ducts
prior to setting the unit.
4. Set the Unit: Lift unit to a point directly above the
curb and duct openings. Guide unit while lowering
to align with duct openings. Roof curbs fit inside
the unit base. Make sure the unit is properly seated
on the curb and is level.
5. Fastening: The installer is responsible for ensuring
that the unit fastening methods are sufficient
to account for the weight and size of these
additionalmodules.
Roof Curb
Side of Unit
Base
1-inch Insulation
E
D
C
A
B
Unit Size A B C D E
ERV-10 1.88 2 1 0.80 0.84
ERV-20 1.88 2 1 0.57 0.75
ERV-45 1.88 2 1 0.81 0.75
ERV-90 1.81 4 1.75 1 0.75
ERV-120 1.94 4.13 1.94 1.13 0.63
All dimensions are in inches.
Curb Cap Details for Factory Supplied Roof Curbs
Unit Size L W
Curb Weight
(lbs.)
Curb
Height
ERV-10 42.75 30.5 50 14
ERV-20 59.25 48.25 75 14
ERV-45 63.75 63.75 125 14
ERV-90 120.5 80.5 520 12
ERV-120 142.25 93 700 12
All dimensions are in inches
Curb Outside Dimensions and Weights
W
L
1 Fan
Wheel
Dia.
1 Fan
Wheel
Dia.
R
o
t
a
t
i
o
n
R
o
t
a
t
i
o
n
R
o
t
a
t
i
o
n
R
o
t
a
t
i
o
n
Length of Straight Duct
GOOD
POOR
GOODPOOR
GOOD
POOR
Tu rning
Vanes
Tu rning
Vanes
SYSTEM EFFECT FACTOR CURVES
FPM X 100
OUTLET VELOCITY
0 5 10 15 20 25 30 35 40 45
1.2
1.0
0.8
0.6
0.4
0.2
0.0
STATIC PRESSURE LOSS
CURVE 1
CURVE 2
CURVE 3
CURVE 4
Recommended Discharge Duct Size and Length
Unit Size Blower Size Duct Size Straight Duct Length
ERV-10 10 9 x 9 3
ERV-20 10 14 x 14 4
ERV-45 12 20 x 20 5
ERV-90L 15 28 x 28 7
ERV-90H 18 32 x 32 8
ERV-120 20 34 x 34 9
All dimensions shown in inches.
• Recommended duct sizes are based on velocities across the
cfm range of each model at approximately 800 feet per minute
(FPM) at minimum airflow and up to 1600 fpm at maximum
airflow. Recommended duct sizes are only intended to be a
guide and may not satisfy the requirements of the project.
Refer to plans for appropriate job specific duct size and/or
velocity limitations.
• Straight duct lengths were calculated based on 100% effective
duct length requirements as prescribed in AMCA Publication
201. Calculated values have been rounded up to nearest foot.
Ductwork Connections
Examples of poor and good fan-to-duct connections
are shown. 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.
1 Fan
Wheel
Dia.
1 Fan
Wheel
Dia.
R
o
t
a
t
i
o
n
R
o
t
a
t
i
o
n
R
o
t
a
t
i
o
n
R
o
t
a
t
i
o
n
Length of Straight Duct
GOOD
POOR
GOODPOOR
GOOD
POOR
Tu rning
Vanes
Tu rning
Vanes
SYSTEM EFFECT FACTOR CURVES
FPM X 100
OUTLET VELOCITY
0 5 10 15 20 25 30 35 40 45
1.2
1.0
0.8
0.6
0.4
0.2
0.0
STATIC PRESSURE LOSS
CURVE 1
CURVE 2
CURVE 3
CURVE 4
Energy Recovery Ventilator10
To Next Page
Loading...
Need help?
General
