Chromalox PF455-3 User Manual
DATE
SALES
REFERENCE
DIVISION SECTION
Chromalox
®
(Supersedes PF455-2)
PF455-3
DH
161-562766-001
FEBRUARY, 2001
4
Chromalox Electric Airduct Heaters
with Fintube Heating Elements
© 2010 Chromalox, Inc.
GENERAL
These heaters are designed to be installed in either a horizontal
or vertical duct in one of the six positions shown in figure 16. The
heater is constructed with individual metal sheath fintube elements
mounted to a heavy gauge metal terminal box.
Due to the various options and materials available, check the
nameplate attached to the heater terminal box with the catalog
number designation system on page 7 before installing to insure
the heater you received conforms to your specification.
Please read these directions carefully to insure all limitations
are properly observed and all wiring and controls are properly
installed and connected.
IMPORTANT — Observe at least one complete heating cycle
operation before leaving the installation.
DHII
Integral Controls
Insert Type
Figure 1
DHIF
Integral Controls
Flanged Type
Figure 3
DHRF
Remote Controls
Flanged Type
Figure 4
DHRI
Remote Controls
Insert Type
Figure 2
Conduit
Entrance Plate
W
H
W
H
W
H
W
H
GENERAL
Limitations: Ductwork must be in accordance with one of the following: Standards of the National Fire Protection Association for
the installation of Air Conditioning and Ventilating Systems of
other than Resident Type (Pamphlet 90A) or Residential Type
Warm Air Heating and Air Conditioning Systems (Pamphlet 90B).
Location: Chromalox Duct Heaters may be located anywhere in
the duct system.
NOTE: The minimum distances shown are limitations. Wherever
possible, locate as far away from these limits as practical. In any
case, this distance with any required airflow correction must be
sufficient to accomplish even air flow at a velocity equal to, at
least, the minimum stated on the heater nameplate.
1. Installation near heat pump, central air conditioner, filters or
humidifier. (Refer to Figure 5).
2. Installation near air handler discharge. (Refer to Figure 6).
3. Installation in branch duct take-off. (Refer to Figure 7).
4. Installation near turns. (Refer to Figure 8). If heater must be
installed closer than 4 feet from the downstream side of a turn,
turning vanes must be installed in the turn. The turning vanes
will straighten out the air flow so it will be uniform over the
face of the heater.
5. Installation with duct transitions in some air distribution systems, the duct heater may be considerably larger than the ductwork and the duct area must be increased by a sheet metal transition. The slope of the transformation piece on the upstream
side of the equipment is limited to 30° as indicated in Figure 9.
On the leaving side, the slope should not be more than 45°.
6. Do not insulate control or terminal box. (Refer to Figure 10).
Leave Control
Box Uninsulated
External
Insulation
Top of Duct
Duct Heater
Air
Flow
30"
Max.
45°
45°
30°
4 Ft. Min.
4 Ft. Min.
Max.
Duct Heater
4 Ft.
Min.
Duct Heater
Here or Here
2 Ft.
Min.
Air Flow
Duct Heater
4 Ft. Min. Straight Section
Air Flow
Duct Heater
4 Ft.
Min.
Air Handler
Air
Flow
Duct Heater
4 Ft.
Min.
Heat Pump,
Central Air Conditioner,
Filters or Humidifier
Air
Flow
-2-
Figure 5
Figure 8
Figure 9
Figure 6
Figure 10
Figure 7
7. Installation in duct larger than heater. For installation where the
duct dimensions exceed the insert type heater dimensions, the
area beyond the heater dimensions must be filled with wire
mesh, expanded or perforated sheet metal of 50% open area as
shown in Figure 11. This will maintain a uniform air velocity
across the face of the duct.
8. Installation with flexible duct. Where a duct heater must be
installed near a flexible duct connection, be certain that a 4’
minimum distance between the duct heater and the flexible
connector exists and that the connector is suitable for 195°F
temperature. (Refer to Figure 12).
9. Do not install duct heater outdoors. Duct heaters cannot be
installed with rooftop equipment where they are exposed to the
weather.
10. Installation with dampers or filters. Maintain at least 4’ distance between duct heater and damper, filter frames, or other
similar obstructions. (Refer to Figure 13).
Clearance: Zero clearance between duct heater and combustible
materials such as wood is permissible. However, adequate clearance must be provided around terminal box for proper ventilation
and future service accessibility.
4 Ft.
Min.
Damper
Air Flow
Top of Duct
Duct
Heater
4 Ft.
Min.
Air
Flow
Duct Heater
Flexible Duct
(Must be suitable
for 195°F)
Inner Baffle
Insert Type
Duct Heater
Remove Bracket and
Use Sheetmetal Screws
Thru Same Holes into Duct.
Oversized Duct
Perforated Metal
(50% Open Area)
-3-
GENERAL
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 nameplate (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 14).
Large ducts will require additional readings taken at locations in
addition to the centerline.
Incoming Air Temperature: Incoming air temperature entering
the duct heater must not exceed 100°F.
Duct Heater
Velocity
Profile
Air Flow
AIR FLOW
Example: 500 FT./MIN. Minimum Air Velocity on Heater Nameplate.
600 200x
500 400x
700 800
Velocity 600 Velocity 900
Profile 900 Profile 600
FT./MIN. 700 FT./MIN. 700
600 200x
500 300x
400x
RIGHT: 500 FT./MIN. MINIMUM WRONG: 9 4500 = 500 FT./MIN. AVERAGE
X – below 500 FT./MIN.
Figure 11
Figure 12
Figure 13
Figure 14
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