heatco HD Series User manual

OEM INSTALLATION INSTRUCTIONS
This Product is intended for installation in Duct or Cabinet mounted
Applications on the Positive pressure side of the circulating air blower
HDR-OEM-MAN-2016-E-1
HD SERIES DUCT FURNACE
RACK ASSEMBLY
WARNING !
Improper installation, adjustment, alteration, service or
maintenance can cause injury or death. Read the installation,
operating and maintenance instructions thoroughly before
installing or servicing this equipment.
The use of this manual is specifically intended for a qualified
equipment manufacturer or installation and service agency. A
qualified manufacturer or installation and service agency must
perform the installation and service of the heating unit.
IMPORTANT

2
MP5157
ANSI Z83.8 (2016) –CSA 2.6M (2016) Gas-Fired Duct Furnace
Table of Contents
Inspection on Arrival ……………………………………..2
Application Guidelines …………………………………..3
Cabinets and Ducts ……… ……………………3
Airflow …………………..………………………….4
Maximum Airflow………………………………….4
Airflow Distribution ………………………………4
Installation Requirements ……..……………………….5
Combustion Air Openings ……………………..5
Airflow Proving Switch ………………………….5
Auxiliary Manual Reset Limit…………………...5
Rack Assembly Installation ………………………………6
Venting System .……………………………………………..7
Condensate Drains …………………………………………8
Gas Supply, Piping and Connections ...………………8
Start-up ………………………………………………………9
Component Identification …………………………………9
Inspection on Arrival
Inspect unit upon arrival for any damage that may have occurred during shipping. If any damage is found, the
consignee should sign the bill of lading indicating such damage and immediately file a damage claim with the
transportation company.
This equipment has been test fired and inspected. It has been shipped free from defects from our factory. However,
shipment and installation may result in loose fasteners, wires and piping connections. It is the installer’s
responsibility to inspect and correct any problems that may have occurred as the result of shipping and
handling during installation.
3035443
HD SERIES DUCT FURNACE

3
Application Guidelines for Duct Furnace Rack Assemblies
This Rack assembly is an engineered, packaged assembly of multiple duct furnaces for application to high
volume airflow systems. The Duct furnaces are ETL Listed under ANSI Z83.8 / CSA 2.6. This product must be
applied in accordance with the requirements of the Duct Furnace Listing and the marked maximum input ratings,
maximum and minimum temperature rise and maximum and minimum airflow.
Cabinet / Duct
This product MUST BE INSTALLED IN A NON-COMBUSTIBLE duct or cabinet and is not designed to have any
portion of a furnace heat exchanger exposed outside the duct or cabinet in which this rack assembly is
housed. The duct furnaces must be located on the positive pressure side of the circulating air blower.
Figure 1 –Typical Installations
Return
Air
Supply
Fan
Supply Air 36.00" Min.
(See Note)
Note: Fan should be spaced sufficient
distance to provide uniform air flow over
heat exchangers. If spacing is not available,
provide air vanes or baffling to evenly
distribute airflow.
6.0"
6.0"
Horizontal Airflow
Horizontal to
Vertical Airflow

4
Airflow
All airflow must be directed over the furnace heat exchangers. Provide proper sheeting to direct airflow over heat
exchanger tubes and eliminate by-pass air. If air tunnel opening is larger than heater profile, provide panels to block
by-pass air and direct all airflow over heat exchanger as shown in Figure 2 below.
Figure 2
22.00"
(Min.) Block-off sheeting
Air Tunnel Width
Air Tunnel
Height
Preferred installation for indirect gas heat section is the last component in the air stream. In this configuration, the
gas heat section is under positive static pressure to ensure that combustion products will not enter the air stream.
Minimum entering air temperature is -40 oF. Maximum discharge air temperature is limited by the maximum plenum
temperature of 180 oF, however the temperature rise across an individual heater group is limited based on airflow
configuration.
Maximum Airflow
When applying duct furnaces, system design should insure that airflow across each heat exchanger provides
sufficient temperature rise under all operating conditions to avoid continuous condensation in the heat exchanger or
flueways. Condensation can occur if flue gases inside the heat exchanger are cooled below their dew point or tube
temperatures drop below the flue gas dew point. Flue gas condensate is corrosive and operating in a continuous
condensing mode or accumulation of condensate can lead to premature heat exchanger failure.
The likelihood of condensing operation increases make-up air units (return air less than 40 oF), modulating heaters
on constant volume airflow applications and applications where duct furnace is over-sized for “typical” heat load and
runs at 50% of maximum input or less the majority of the time.
Flue gas condensate is corrosive and will result in shortened heat exchanger life, if not properly drained.
For modulating applications variable air flow is preferred. In constant volume airflow systems a dampered air bypass
may be required to reduce airflow over furnaces, to provide necessary airflow across modulating furnace and
maintain required minimum rise (assume even airflow over furnaces ei. Total air flow / No. of furnaces)
Airflow Distribution
Uniform air distribution over the heat exchanger is essential to proper operation and optimum unit efficiency.
Circulating air blower must be located and properly positioned to the Heater rack assembly to provide uniform airflow
across the heat exchangers. Locating the circulating air blower too close to the unit creates uneven airflow over the
heat exchanger resulting in poor performance and possible damage to heat exchanger. Never locate heaters closer
than 24” (610mm) from circulating air fan. In most applications, this distance will need to be greater to provide
uniform airflow. Use of baffles and/or turning vanes may be required to provide uniform air flow through heating unit.
Failure to provide well distributed airflow over the heating units will result in reduced performance and possibly
premature failure of heat exchanger(s) due to overheating.

5
Installation Requirements
All unit installations must be in accordance with the National Fuel Gas Code ANSI Z223.1 (NFPA 54) in the United
States and Can/CGA-B149 Installation Code in Canada, and all other applicable local codes and ordinances. These
requirements include but are not limited to:
Combustion air supply to the heating equipment
Venting of the products of combustion (flue gases)
Gas supply, piping and connections
Unit Location and clearances
All electrical equipment must be grounded and wired be in accordance with the National Electric Code (ANSI/NFPA
70) in the United States, and the Canadian Electric Code (CSA C22.1), in Canada. The installer / equipment
manufacturer is responsible for final compliance with these requirements.
FM Requirements
1. FM requires that all units must be listed by a Nationally Recognized Testing Laboratory (NRTL). The HD
Series heaters are listed by ETL / Intertek an NRTL.
2. The High Limit must be located in a circuit that does not exceed 120 VAC. Limits are all located in 24 VAC
circuit.
IRI / GE CAPS Requirements
1. All input sizes require 100% shut-off. Units are equipped with a 100% safety shut-off control that will lockout
on ignition failure.
2. Units must use controls that are UL or CSA listed. All our controls comply
3. Models with inputs of 150,000 to 400,000 Btuh require “mechanical exhaust” and a safety interlock. All HD
Series heaters are power vented and employ an air pressure switch on the combustion air blower.
The requirement for an FM or IRI gas train applies only to individual units having an input in excess of 400,000 Btuh.
The individual duct furnaces provided in this assembly are 400,000 Btuh or less and are individually controlled by
their own safety shut-off control.
Combustion Air Openings
Openings for ambient combustion air must be provided in a panel or door with direct access to the vestibule
area where the burners and combustion air fan assembly are located. Air opening(s) must be sized to
provide a suitable supply of combustion air for to the burner compartment and have a minimum free area of
1 sq. in. (625mm2) per 4,000 Btuh (2,345 W) of rated total input. The minimum dimension of any air opening
must be at least 3 inches.
Indoor combustion air supply is acceptable provided that sufficient air exchange is provided from outside to the space
containing the rack assembly. Ducted air supply may be required for installations in a mechanical room or space. Air
supply to the duct furnace must be free from any corrosive vapors.
Airflow Proving Switch
Provide an air flow proving switch interlocked with the system heat enable, to insure circulating airflow over
the heat exchangers, prior to initiating ignition of heater(s). The duct furnaces are equipped with individual fixed
temperature high limit switches, which are of the auto recycle type and will turn-off the gas to the heaters when
maximum temperature is reached. However, the heaters will cycle back on when the temperature in the duct or
cabinet drops. In high heat applications, this cycling can lead to panel warpage and possible air leakage, heat
damage to components and wiring and create a possible fire hazard. The air flow proving switch prevents a call for
heat to the heater controls when lack of airflow could result in a cycling heater condition.
Auxiliary Limit Switch
For additional safety in the event of low airflow conditions due to filter blockage, coil blockage and or damper failure,
a manual reset auxiliary limit is required, mounted downstream of the rack assembly to sense elevated duct
temperatures.

6
Rack Assembly Installation
A Nameplate/ Rating Plate is attached to each individual duct furnace to identify the model and serial number of
this product. This label also contains information including gas type, maximum and minimum input rating,
manifold pressure, maximum and minimum inlet gas pressure, maximum and minimum airflow requirements,
output capacity and electrical ratings for each individual furnace. This label must be left attached when the
module is installed in the product for identification purposes.
1. Verify that the rating plate information matches the gas and electrical supply provided at the
installation sight. Refer to Rating Plate attached to individual heaters in the assembly.
2. Carefully support and lift module into position and slide into cabinet or duct. Provide proper support or
rigging using the labeled handling points on the rack assembly frame to position in cabinet or duct. Fasten to
cabinet or duct.
3. Provide removable access panels in ductwork or cabinet immediately upstream and downstream of duct
furnace rack assembly to allow for inspection of the heat exchanger. These openings should be large
enough to observe smoke or reflected light inside the casing to inspect heat exchanger for leaks, and to
check for hot spots on the heat exchanger due to poor air distribution or insufficient air volume. Attach covers
so as to prevent air leakage.
4. Install air flow proving switch interlocked with the system heat enable, to insure circulating airflow
over the heat exchangers, prior to initiating duct furnace operation.
5. Locate and mount electrical control panels or junction boxes to prevent overheating of and damage to
controls. Maximum temperatures for these components range from 160 oF to 190 oF. Flue gas vents may
reach temperatures of 480 oF. Be sure to provide ample clearance between controls and vent
components. Controls should never be located directly over vent piping.
6. Provide necessary support for wiring in vestibule. Wiring should not contact metal surfaces with may
be hot during module operation.
7. Complete electrical field connections to the distribution control panel provided. Modulating units require a
0-10VDC Analog signal. Wiring Diagrams for heaters and distribution are provided in the information packet
containing these instructions. These diagrams include information for the inclusion of addition of field applied
safety devices
8. Connect and secure venting system to individual heater combustion blowers. Seal joints with high
temperature silicone sealant to prevent recirculation of flue gases into combustion air supply.
9. Connect gas supply piping to 2” NPT gas header provided on assembly. All Gas Piping and
connections must be pressure / leak tested before putting equipment into service. See specific
requirements, guidelines and warnings for gas piping and connection in next section before completing.
10. Perform electrical and operation checks on completed assembly. Refer to Duct Furnace Operation,
Service, and Maintenance Manual. Refer to heater sequence of operation and “Start Up and Operation”
Instructions provided.
11. Additional documents provided with this assembly include (1) HD Series Operation, Service and
Maintenance Instructions, (2) Wiring Diagrams and Sequence of Operation for the individual heater control
systems, (3) Heater Wiring Diagram for the Stage controller (if provided) and (4) Operating and Service
Instructions for the Stage Controller. These instructions and diagrams must be included with the
equipment in which the rack assembly is installed for field start-up and service reference.
WARNING !
Duct Furnaces are not designed for use in hazardous atmospheres
containing flammable vapors or combustible dust, or those containing
chlorinated or halogenated hydrocarbons, or airborne silicone substances.

7
Venting System
A properly designed venting system must be provided to discharge the products of combustion (flue gases) to the
outdoors. See “Installation Requirements” for reference to applicable standards and codes. For outdoor applications
a Vent Riser / Vestibule Kit is available. See Figure 3.
Figure 3 –Outdoor Venting
18" Min. Above
Top of AHU
Cabinet Flue Riser
Weather proof
Vestibule Enclosure
Cover Hood
Combustion Air Opening
For Indoor installations which are vertically vented, a flue header assembly with properly sized flue collar is available.
See Figure 4.
Figure 4 –Indoor Vertical Venting
AHU Cabinet
Heat Section
Combustion air
opening
Custom
Venting System.
Vestibule area
(Isolated from
circulating air
stream)
Listed Vent Cap
Condensate
Drain
Custom Adaptor
Note: Horizontal and Separated combustion venting systems require a “Special Venting” system design.
The venting system must be properly designed for the specific application by a manufacturer / provider of listed type
venting systems. Contact Precision Vent, Inc. at 678-461-5997 or www.precisionvent.com ,or a manufacturer of
Approved Venting Materials and systems for design assistance.
WARNING !
Improper venting poses a Carbon Monoxide (CO) Hazard. Failure
to provide a properly designed venting system may result in poor
performance, unsafe operation and injury or death.

8
Gas Supply, Piping and Connections
1. Gas valves on the heating units are suitable to a maximum inlet pressure of ½ PSI (13.5” w.c.) on Natural
or LP gases. If the main gas supply pressure is greater than 13.5” w.c., a step down pressure regulator must
be field installed.
2. Supply Gas piping and gas regulators must be sized for the total Btu input of all units (heaters) serviced by a
single supply. Be sure that gas regulators servicing the assembly have the proper pipe and internal orifice
size for the total input of the rack assembly.
3. Duct furnaces require a minimum inlet gas pressure of 5.0 “w.c for individual heaters are rated at 400,000
Btuh or less and 6.0 “w.c for individual heaters rated higher than 400,000 Btuh.
4. Provide a drip leg (sediment trap) and manual shut-off valve immediately upstream of the rack assembly
2” NPT main gas header as shown. To facilitate servicing of the unit, installation of a union is recommended.
5. A 1/8” NPT tap is provided on the supply header. A fitting suitable for connection to a pressure gauge
capable of measuring gas pressure should be connected to all assemblies serviced by a single regulator.
Verify pressure setting with all heaters in operation.
6. In some areas, local codes or insurance carriers may require the installation a of a low gas pressure switch.
An additional 1/8” NPT tap is provided on the supply header for connection of a gas pressure switch. Use a
listed, ventless gas pressure switch set at 5.0” w.c. if required.
7. Flexible gas connectors from main gas header to individual heater manifolds are shipped loose to avoid
possible damage due to vibration during shipping. Connect flexible gas lines between main gas header and
individual heater sections prior to connecting main gas supply to header.
8. Pressure / leak test all connections prior to putting unit in service. See Warnings below to insure that
pressure testing is completed in accordance with the Listing standard for the Duct Furnace.
WARNING !
WARNING !
1. All field gas piping must be
pressure / leak tested prior to
operation. NEVER use and open
flame to check for leaks. Use a
soap solution or other leak
detecting solution for testing.
2. Gas pressure to appliance
controls must never exceed 13.5”
w.c. (1/2 PSI)
1. When pressure testing at ½ PSI or
less, close the manual shut-off
valve on the appliance before
testing.
2. When pressure testing gas supply
line at ½ PSI or higher, close
manual gas valve and disconnect
heater from supply line to be
tested. Cap or plug the supply
line.

9
Condensate Drains
Duct Furnace rack assemblies are listed for installation downstream of refrigeration systems, and are provided with
pre-piped condensate drain lines. On assemblies employing modulating units, condensation may occur for a short
period of time after heater start-up. On outdoor applications employing modulated heaters, the condensate drain
should have freeze protection for the last 12” (305mm) before the discharge end.
Start-Up
Initial field start-up should be completed by a qualified service technician or agency. If factory installed, the assembly
should be test fired and operating sequence verified prior to shipment of the equipment. Refer to the Operating,
Service and Maintenance Instructions provided.
Instructions are provided for the individual duct furnaces in the assembly. Refer to the Operating, Service and
Maintenance Instructions provided for heater operation and start-up procedures.
Component Identification
Heatco Inc.
50 Heatco Court
Cartersville, Ga. 30120
Main Gas Header
Heater Electrical
Control Panels
Combustion
Air Fan
Manual Gas
Shut-off Valve
Combination
Gas Valve
Modulating
Valve
Condensate
Drain Line
Comb Air
Pressure Switch
Heater Gas
Manifold
Insulated
Vent Duct
Flexible Gas
Connector