6
Example: 500 FT./MIN. Minimum Air Velocity
on Heater Nameplate.
Velocity
Profile
Ft./Min.
600
Velocity
Profile
Ft./Min.
200x
500
400x
700
800
600
900
900
600
700
700
600
200x
500
300x
400x
RIGHT:
500 Ft./Min.
Minimum
WRONG:
9 4500 =
500 Ft./Min
Average
Multiple Duct Heaters: Up to six duct heaters may be
combined into a heating bank as shown in Figure 11.
When called for on order, brackets will be furnished for
fastening flange type duct heaters together to form a
bank. Heater will be coded for proper assembly in the
field.
Two to six duct heaters (with flange) may be installed in
a horizontal or vertical duct.
Heaters must be mounted in the position designated
by arrows on the heater frame. (Refer to Figure 12).
The heater terminal box on vertical duct installations
can be located on any side of the duct but for horizon-
tal duct installation the terminal box must be on the
side of the duct.
Mounting
Figure 11
Flow through duct heater must never drop below the
minimum air velocity shown on duct heater nameplate.
If the air handling system includes filters, they must be
cleaned whenever necessary in order to maintain air
flow above the minimum, otherwise poor temperature
control and discomfort will result.
If air flow is poorly distributed within the duct, deflector
vanes must be added to provide correction.
The minimum air velocities shown on the nameplate
are not to be considered average readings. Do not add
various velocities taken across the face of the duct,
find an average value, and compare it to the minimum
velocity shown on the heater nameplate.
The minimum air velocity refers to any point along the
face of the duct heater when checking duct velocities,
no velocity can be below that sown on the heater name-
plate (remembering inlet air temperature). Velocities are
best checked with an anemometer, taking numerous
readings along the horizontal and vertical centerline
of the duct heater at the location prior to installation
or slightly up stream from the heater after installation.
(Refer to Figure 10). Large ducts will require additional
readings taken at locations in addition to the centerline.
Figure 10
Duct Heater
Velocity
Profile
Air Flow
Incoming Air Temperature: Incoming air temperature
entering the duct heater must not exceed 100°F.
Air Flow
