Installation Supplements
Refer to the appropriate Greenheck installation
supplements for special requirements
(www.greenheck.com links are underline):
• IDHE-O Outdoor Applications
• T725 Thermostat Installation Instructions
• T725 Thermostat Operation Instructions
• T855 Thermostat Installation Instructions
• T855 Thermostat Operation Instructions
Online version to this Installation
instructions at www.greenheck.com.
These instructions apply to zero clearance installation of electric duct heaters within ducts. They are approved for
use with heat pumps, air conditioners, or other forced air systems and may be controlled by contactors, relays,
sequencers, or solid state devices.
Greenheck duct heaters are pre-wired, factory tested, and furnished with integral controls.
Receiving and Handling
Upon receiving heater, check for both obvious and
hidden damage. Check all insulators for breakage and
inspect heater element wire(s) for any deformation
or damage that could cause a short circuit to
ground. Make sure all fasteners are tight. Electrical
connections such as pressure terminals should be
checked for tightness. If damage is found, record all
necessary information on the bill of lading and file
a claim with the final carrier. Check to be sure that
all parts of the shipment, including accessories, are
accounted for.
Heaters must be kept dry and clean. Indoor storage
and protection from dirt, dust and the weather is
highly recommended. Do not store at temperatures in
excess of 100°F (38°C).
This manual is the property of the owner and is required
for future maintenance. Please leave it with the owner
when the job is complete.
Safety Warning
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, injury
or death. Read the installation, operating, and
maintenance instructions thoroughly before installing
or servicing this equipment.
“UL Listed (see complete marking on product)
ANSI/UL Standard 1996 (File E366239)
IDHB and IDHE series are intended for installation
in accordance with electric heaters requirements
established by:
National Fire Protection Association
NFPA Standards 90A and 90B
NFPA Standard 70
General Information
Table of Contents
General Information . . . . . . . . . . . . . . . . . . 1
Electrical Guidelines . . . . . . . . . . . . . . . . . . 2
Minimum Air Velocities . . . . . . . . . . . . . . . . 2-3
Installation . . . . . . . . . . . . . . . . . . . . . . 4-5
Insulated Duct Installation . . . . . . . . . . . . . . . 6
Installation Details with SSR Controllers. . . . . . . . 7
Installation Details for Staged Heaters. . . . . . . . . 8
Thermostat Connection Information . . . . . . . . 9-10
Troubleshooting Guide . . . . . . . . . . . . . . .11-12
IDHB and IDHE
Duct Heaters
®
Electric Duct Heaters 1
Document 478052
IDHB and IDHE
Duct Heaters
Installation, Operation and Maintenance Manual
Please read and save these instructions for future reference. Read carefully before attempting to assemble, install,
operate or maintain the product described. Protect yourself and others by observing all safety information. Failure
to comply with these instructions will result in voiding of the product warranty and may result in personal injury
and/or property damage.
Electrical Requirements
Refer to the wiring diagram on inside of cover. Make
sure line and control voltage of system matches that
noted on wiring diagram.
Wire in accordance with N.E.C. and any existing local
codes. Check tightness of all factory and field electrical
connections. Make sure fan interlock is wired in if the
Duct Heater does not have an air flow switch.
Use 90°C (194°F) copper wire.
Control must be wired for N.E.C. Class 1 unless
otherwise specified.
When heater has integral transformer for control voltage
to thermostat, use thermostat with isolating contacts to
prevent interconnection of Class 2 outputs.
Disconnect all electrical power before servicing.
When servicing heater, make sure all components are
repositioned in the proper location and reconnected per
the wiring diagram.
Replacement parts must be identical to the original
components. Contact factory for replacement parts.
Minimum Air Velocities
The minimum uniform airflow in a duct heater is directly
related to the inlet air temperature. Consideration must
be given to both airflow across the heater and inlet air
temperature, (shown at right).
1. To calculate the watts per sq. ft. of duct area,
divide the total watts required by the duct area.
EXAMPLE: Duct Size = 2ft. x 3ft.
Total watts = 20,000
W/Sq. Ft. = 20,000 = 3333
6
2. If the air handler equipment is expressed in
fpm, then a direct cross reference can be made
by comparing the temperature of the air (as it
enters the Duct Heater) to the kW rating on the
chart of rated velocity.
a. Draw a line horizontally from the Watts/Sq. Ft.
required to the inlet air temperature being used.
b. From this point of intersection on the Inlet Air
Curve, draw a line down vertically to establish
the air velocity.
c. The velocity should never be lower than the
velocity as determined from the chart. In cases
where this is not true, the velocity must be
increased or the kW required must be reduced.
3. In cases where the air handling equipment is
expressed in CFM, convert to FPM by dividing
the CFM by the duct area.
EXAMPLE: FPM = CFM
Duct Area
1,400
4,000
6,000
8,000
10,000
12,000
14,000
16,000
18,000
20,000
WATTS PER SQUARE FOOT, DUCT AREA
22,000
Minimum Air Velocity (fpm)
2,000
1,2001,000800600400200
BELOW 78°F INLET AIR
78° TO 90°F INLET AIR
91° TO 110°F INLET AIR
Note: Minimum airflow must be maintained at any
point over the face of the heater. The velocity of air
should NEVER be lower than the specified minimum.
In cases where this is not true the KW must be
reduced or the velocity of air increased.
Note: Observe at least one complete heating cycle to
insure that cycling of the safety limit controls does not
occur before leaving the installation.
IDHB: Minimum Air Velocity
Electric Duct Heaters2
IDHE: Air Flow Requirements
Minimum Air Velocity: See charts below
Maximum Inlet Air Temp: 110°F
Maximum Heater KW: 30 KW per Square Foot of Duct Cross Section
Electric Duct Heaters 3
Installation
Failure to follow instructions will void all warranties. For safe operation and best performance, the following
installation procedures must be adhered to.
Note: Do not “Bank “ heaters (side by side). If greater capacity is required, proportion smaller heaters in separate
runouts. Heater control boxes must be completely accessible and located to provide ventilation at all times.
Duct Orientation
Heaters may be installed in the vertical sides of
horizontal or vertical ducts but never in the top or
bottom of a horizontal duct. Heaters are approved for
airflow in both directions when installed in horizontal
duct.
IDHB: Heaters installed in vertical ducts are tested and
approved for up airflow only!
IDHE: Heaters installed in vertical ducts are tested and
approved for up and down airflow.
1. Install heater a minimum of four feet:
- From heat pumps or central air conditioner
- Downstream from an air handler
- From any canvas duct connector or transition
in duct size
- Downstream from an air filter
- Upstream from a humidifier
2. At least 2 feet either side of an elbow or turn.
Control Cabinet Orientation
IDHB: The control cabinet must be positioned as
labeled on the unit.
IDHE: The control cabinet offset may be positioned in
either direction as chosen by the installer.
Slip-in Heater: To install a slip-in heater (Figure 1),
cut an opening as required in the side of the duct.
Slide heater in the duct using the control box as
template to mark the mounting screw holes. Remove
unit and drill mounting holes. Mount unit to duct with
sheet metal screws. Connect high and low voltage
supplies along with fan interlock circuit (if no airflow
switch is furnished). Larger heaters may require
hangers. Connect high and low voltage supplies as
required.
Flange Heater: To install a flange type heater (Figure
2), insert heater between two sections of flanged
duct, and bolt in place. For additional strength, the
duct flange should be doubled as shown in the figure.
Large heaters may require hanger straps. Connect
high and low voltage supplies along with fan interlock
circuit (if no airflow switch is furnished).
SLIP-IN HEATER
FIGURE 1
FIGURE 2
FLANGE HEATER
HEATING
ELEMENTS
TERMINAL OR
CONTROL BOX
WRAPPER
WRAPPER
TERMINAL OR
CONTROL BOX
HEATING
ELEMENTS
1"
1"
DOUBLE
LIP
SLIP-IN HEATER
FIGURE 1
FIGURE 2
FLANGE HEATER
HEATING
ELEMENTS
TERMINAL OR
CONTROL BOX
WRAPPER
WRAPPER
TERMINAL OR
CONTROL BOX
HEATING
ELEMENTS
1"
1"
DOUBLE
LIP
Electric Duct Heaters4
Figure 3: IDHE orientation
Airflow Switch: When furnished, ensure the airflow switch is plumbed appropriately for the given duct condition.
The pickup tube must be connected to the switch port labeled “LOW” if the duct is negatively pressurized and the
opposite port if positively pressurized.
Note: An airflow switch only proves that airflow exists (a differential in static pressure), not that the minimum air
velocities and proper air distribution for the duct heater exist.
Electric Duct Heaters 5
Insulated Duct Installations
Duct with External Insulation
The external insulation is to be removed from
the area where the heater is mounted.
Note: Size of heater is based on the duct size
(no recess required).
Duct with Internal Insulation
S-type with internal insulation left in place or duct constructed from insulation board
Recess = Insulation Thickness
Note: Size of heater is based on the following:
Heater ‘H’ = Duct ‘H’ - (Insulation Thickness x 2)
Heater ’W’ = Duct ‘W’ - Insulation Thickness
(recess required)
Internal insulation cut away
The internal insulation is to be removed from the
area where the heater is mounted
Recess = Insulation Thickness
Note: Size of heater is based on the duct size
(recess required).
Electric Duct Heaters6
Installation Details for Electric Duct Heaters Equipped with SSR’s
(including SSR Vernier Control)
SSR controlled heaters will need to be supplied with
a 0 to 10 VDC, 2 to 10 VDC, or a 4 to 20 mA signal
generated from the building’s automation system or a
local thermostat.
The configuration dipswitch is used for setting up the
common input type. Using a pen point, gently push the
switch up for on and down for off according to the setup
outlined in the table below.
Command Input 1 2 3 5
0-10V OFF OFF ON OFF
4-20mA OFF ON OFF ON
2-10V OFF OFF ON ON
0-135R
4-20m A
0-10V
CYT A
4-20m A
CYT B
Electric Duct Heaters 7
Installation Details for Staged Electric Duct Heaters
For Standard Non-SSR Heater only!
Electric Duct Heaters8
Thermostat Connection Information
Electric Duct Heaters 9
Thermostat Connection Information cont....
Electric Duct Heaters10
A duct heater must be installed according to the
installations instructions, wiring diagram and labeling
supplied with the heater.
Listed below are some important items when installing
an electric duct heater:
1. Never operate a duct heater without airflow.
The heater must always be interlocked with the
fan. This may be accomplished by either an
airflow switch or fan interlock relay.
2. Never operate heater without achieving at least
the minimum airflow required. Always refer to
the installation instructions and the nameplate
label to determine minimum air velocities based
on inlet air temperature. If the minimum airflow
requirements are not present the heater will not
function properly and safely
(see Figure 4).
3. Never operate the heater with uneven airflow.
The minimum airflow requirements must be
present at all points over the heater face (see
Figure 4).
4. The air must be filtered. The incoming air must
be free from all debris, combustible particles,
and hazardous vapors.
5. Locate the heater at least 24 in. from an elbow
or turn (see Figure 5).
6. Locate the heater at least 48 in. from the
following (see Figures 6-10):
• heat pump or central air
• canvas duct connector or transition
section for change in duct size.
• downstream from an air handler.
• upstream from a humidifier
• downstream from an air filter
• fan
7. Never install a standard heater into a duct with
an internal obstruction. An obstruction can
block airflow at the temperature limit controls
and element terminations. If this situation exists,
it can be corrected by using a heater with
recessed control box and reduced wrapper size.
This situation is common with internally insulated
ducts (see Figure 11).
8. Never insulate the exterior of the control box.
The control must be completely accessible and
located where ventilation can be provided at all
times (see Figure 12).
9. Never install a heater near a double blower
outlet. A heater must be installed far enough
away from a double blower outlet so that even
and proper airflow is present or separate duct
heaters placed in the duct runouts of each
blower (see Figure 13).
500 fpm
470 fpm
780 fpm
EXAMPLE: IF 780 fpm IS REQUIRED
EXAMPLE: IF 780 fpm IS REQUIRED
EXAMPLE: IF 780 fpm IS REQUIRED
CORRECT
MIN. AIRFLOW AND EVEN AIR
DISTRIBUTION ARE PRESENT
INCORRECT
MIN. AIRFLOW AND EVEN AIR
DISTRIBUTION ARE NOT
PRESENT
INCORRECT
MIN. AIRFLOW IS NOT PRESENT
FIGURE 4
470 fpm
470 fpm
780 fpm
780 fpm
780 fpm
780 fpm
FIGURE 5
FIGURE 6
Heat Pump or Air Conditioner
24" MIN.
48" MIN.
HEAT PUMP OR
AIR CONDITIONER
HEATER
HEATER
DUCT
DUCT
FIGURE 6
Heat Pump or Air Conditioner
48" MIN.
HEAT PUMP OR
AIR CONDITIONER
HEATER
DUCT
10. Never use aluminum conductors. Use copper
conductors only for all incoming wiring.
11. Never install a standard heater outdoors without
making special provisions to protect the heater
and control box from the elements.
12. Never bundle, tie or wrap power wiring. The
wire could overheat or the insulation could
breakdown.
13. Never use a different voltage and/or phase than
what is listed on the heater nameplate label. The
duct heater is to be used only at the voltage and
phase that is listed on the nameplate label.
Note: An airflow switch only proves that airflow exists
(a differential in static pressure), not that the
minimum air velocities and proper air distribution
for the duct heater exist.
Troubleshooting Guide
Electric Duct Heaters 11
Troubleshooting Guide cont....
DUCT W/ INTERNAL INSULATION
DUCT W/ EXTERNAL INSULATION
CORRECT
INCORRECT
CORRECT
INCORRECT
FIGURE 11
FIGURE 12
FIGURE 13
INCORRECT
DUCT W/ INTERNAL INSULATION
DUCT W/ EXTERNAL INSULATION
CORRECT
INCORRECT
CORRECT
INCORRECT
FIGURE 11
FIGURE 12
FIGURE 13
INCORRECT
DUCT W/ INTERNAL INSULATION
DUCT W/ EXTERNAL INSULATION
CORRECT
INCORRECT
CORRECT
INCORRECT
FIGURE 11
FIGURE 12
FIGURE 13
INCORRECT
FIGURE 8
Air Handler
FIGURE 9
Humidifier
FIGURE 10
Air Filter
AIR HANDLER
HEATER
HEATER
HUMIDIFIER
AIR FILTER
HEATER
48" MIN.
48" MIN.
DUCT
DUCT
DUCT
48" MIN.
FIGURE 8
Air Handler
FIGURE 9
Humidifier
FIGURE 10
Air Filter
AIR HANDLER
HEATER
HEATER
HUMIDIFIER
AIR FILTER
HEATER
48" MIN.
48" MIN.
DUCT
DUCT
DUCT
48" MIN.
FIGURE 8
Air Handler
FIGURE 9
Humidifier
FIGURE 10
Air Filter
AIR HANDLER
HEATER
HEATER
HUMIDIFIER
AIR FILTER
HEATER
48" MIN.
48" MIN.
DUCT
DUCT
DUCT
48" MIN.
INCORRECT
CORRECT
FIGURE 7
Transition Change
HEATER
48" MIN. 48" MIN.
HEATER
DUCT
DUCT
478052 • IDHB IDHE Series, Rev. 8, January 2022 Copyright 2022 © Greenheck Fan Corporation12
As a result of our commitment to continuous improvement, Greenheck reserves the right to change specifications
without notice.
Product warranties can be found online at Greenheck.com, either on the specific product page or in the literature
section of the website at Greenheck.com/Resources/Library/Literature.
®
Phone: 715.359.6171 • Fax: 715.355.2399 • Parts : 800.355.5354 • E-mail: [email protected] • Website: www.greenheck.com
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