Indeeco process Installation, Operating, & Maintenance Instructions

INSTALLATION, OPERATING

&

MAINTENANCE INSTRUCTIONS FOR

CAUTION

CAUTION

WARNING

ELECTRIC PROCESS AIR HEATERS

INDEECO Process Air Heaters are designed to provide
years of trouble free operation if properly installed and
maintained. Please read and follow these instructions for
installing and maintaining the heater.

GENERAL

element is directly related to its surface temperature.
Follow the limitations of Table 1 for maximum watt densities
and minimum airflows. The watt density is shown on the
heater nameplate.

INDEECO process air heaters are designed and intended
for installations in plenums or ducts to heat forced air in
industrial equipment and systems. A variety of designs and
sizes are available with outlet air temperatures up to
1200°F. Due to these high temperatures, the heater design
features must be closely matched to the application.

There are three types of heating elements:

• Open Coil - a bare (electrically hot) resistance wire coil

• Finned Tubular - a spiral finned metal sheathed element

• Tubular – a tubular metal sheathed element.

Open coil elements require clean, uniform airflow and can
only be mounted with the coils horizontal. They should not
be used where there could be contact with the coils by
personnel or electrically conductive material.
Finned tubular elements can tolerate moisture and a
degree of non-uniform airflow. Finned tubular elements
should not be used where contaminants are likely to build
up between the fins.
Tubular elements are universally applicable. Tubular and
finned tubular process air heaters can be mounted with the
elements either vertical or horizontal.

The heating elements are available in various watt density
ratings. Outlet temperature, watt density and airflow
velocity determine the surface temperature of the open coil,
tubular or finned tubular elements. Life of the heating

INSTALLATION

There are two types of heater frames:

• A sheet metal frame for slip-in duct mounting is
standard for 250°F rated units (Figure 1).

• A plug-type design with mounting plate is standard for
400°F through 1200°F rated units (Figures 2 & 3).

All open coil process air heaters, and the 250°F finned
tubular process air heaters, have top and bottom frames
that restrict the airflow to either horizontal or vertical, while
all other process air heaters can be used with any
perpendicular air flow direction.

Instructions for Industrial Control Panels are provided in
87-2000-83. A section on control methods is included.

Failure to follow INDEECO recommendations could
result in premature failure and/or serious equipment
damage.

Temperature regulating devices, temperature limiting
controls, and low flow controls are recommended for use
with process air heaters to control the heating process and
safeguard the heater from excessive temperatures that can
cause damage.

Mechanical Instructions

INDEECO recommends installation be performed by
qualified personnel familiar with the National Electrical
Code and all local codes and standards. It is the
responsibility of the installer to verify the safety and
suitability of the installation

WARNING

Hazardous voltages are present in this equipment. Lock
out and tag the branch circuit disconnect switch before
working on this heater.

Handling and Storage
Care must be taken to avoid damage to the heater during

storage and handling. Protect the heater from weather
damage during storage if shipping packaging is not sealed.

It is recommended to store the heater in a cool dry area to
help prevent the heating elements or ceramic spacers from
drawing moisture.

Site Selection
Review the NEMA Type rating of the heater provided. Do

not install a heater in an area not consistent with its rating.

DO NOT mount heaters in an atmosphere containing
combustible gases, vapors, dusts, or fibers.

Allow at least three feet in front of the heater terminal box
for heater maintenance. Consideration should also be
given for heater removal clearance to allow heater
replacement.

Electric heaters are capable of developing high
temperatures. Therefore, extreme care should be taken to
avoid mounting heaters in an atmosphere containing
combustible gases, vapors, dusts, or fibers unless properly
marked as suitable for the condition.

If the duct or plenum is insulated, be sure that insulation
does not block airflow across the heating elements. Insure
that the airflow is uniform across the face of the heater to

2

avoid hot spots. Typical causes for uneven airflow are

WARNING

structural components blocking air or mounting the heater
too close to elbows, transitions or the fan. A pressure plate
on the heater inlet should be considered if uneven airflow is
expected.

The heater should be mounted plumb horizontally and
vertically to assure proper operation. If the heater is
installed horizontally and weighs over 25 pounds, support
rails or hangers must be provided in the duct or plenum for
support.

WARNING

Do not cover the heater terminal box or install the heater
so that part of the terminal box is within the duct or plenum.
Dangerous over-heating of the wiring could result.

Slip-In Duct Mounted Construction (Figure 1)

1. Determine proper mounting for airflow direction.

2. Cut a hole into the duct or plenum to accommodate
the body of the heater (excluding the terminal box).
The hole should be at least 1/8” larger than the
frame.

3. Slip the heater into the opening, center and attach
the back of the terminal box to the duct or plenum
using sheet metal screws.

4. Do not mount an open coil heater with the coils in a
vertical position.

Plug-Type with Mounting Plate Construction (Figures 2 & 3)

1. Determine proper mounting for airflow direction.

2. Cut hole into the duct or plenum to accommodate
the body of the heater (excluding the mounting
flange). This hole should be at least 1/8” larger than
the frame.

3. Supply a mating flange, weld studs or bolt holes to
match the mounting flange.

4. Supply a gasket between the mounting and mating
flanges.

5. Do not mount an open coil heater with the coils in a
vertical position.

Electrical Instructions

Field supplied conductors must be sized for at least 125%
of the circuit current.

To calculate the circuit current (in amps):

KW x 1000Single phase

Line current Line Voltage

KW x 1000Three phase

Line current 1.732 x Line Voltage

Wiring to the heater should be permanently installed in
metallic or non-metallic electrical grade conduit in
accordance with all applicable electrical codes, and should
include a grounding conductor if non-metallic conduit is
used.

Field supply wiring must be rated for 600Vac. Use copper
conductors. 450oC wire may be required on high
temperature heaters. If the wire is not available locally,

please contact INDEECO.
The electrical installation should include a service

disconnect switch in sight of the heater as well as branch
circuit over-current protection and over-temperature
protection (if not provided with the heater).

For wiring recommendations refer to the wiring diagram. An
additional copy is provided inside the heater terminal box.

INDEECO strongly recommends the use of an outlet air
over-temperature control device located near the heater
outlet. A thermostat or thermocouple (with remote
controller) set approximately 50°F above the normal
operating temperature may be used. Additionally, a
differential pressure switch or a fan interlock relay may be
used to detect air pressure or fan motor operation. This will
prevent the heater from operating without airflow.

Where thermocouple extension wire is required between the
heater and control panel, verify it is connected with proper
polarity as shown on the wiring diagram. Failure to do so
may result in an uncontrolled heater. Refer to the wiring
diagram for the required wire type. Shielded wire is
recommended to reduce signal interference.

The potentially high operating and ambient temperatures of
process air heaters require field wiring to the heater to be
carefully matched to the application to avoid serious injury
or damage to the equipment. The wiring must be de-rated
for the expected terminal box temperature.

The size and type of incoming field wiring will depend upon
the heater terminal box temperature, heater current draw
per conductor, number of conductors per conduit, and wire

insulation rating. Refer to the National Electrical Code.
The terminal box temperature is directly related to the

heater outlet air temperature. Insulated terminal boxes are
provided on high temperature heaters to allow moisture
seals on tubular and finned tubular heating elements, and to
avoid costly high temperature wire. Refer to Table 2 for the
INDEECO estimated terminal box temperature.

Retighten all electrical connections that may have
loosened during shipment. Failure to do so may result
in damage to the heater or risk of fire.

When making connections directly to the element terminals
on tubular or finned tubular elements, apply a ¼” wrench to
flat sections of the element terminal immediately below the
threads. Otherwise, damage to the terminal may result.

Confirm all unused conduit holes in the terminal box are
sealed with plugs suitable for the heater environment.

Attach a ground conductor to the ground lug located in the
heater terminal box or by other appropriate means per NEC
Article 250.