Sterling TD Series 400,000 BTU Tubular Duct Furnace, Natural Gas, Aluminized Steel Heat Exchanger

Sterling TD Series 400,000 BTU Tubular Duct Furnace gas-fired indoor duct furnace with exposed horizontal tubular heat exchanger.

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Sterling

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Model

TD400A1NS111

240042

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Product Features

400,000 BTU Heating Output
82% Efficient Heating Performance
Durable 20-Gauge Aluminized Steel Heat Exchanger
Natural Gas Heating Operation
Heavy-Duty 20-Gauge Steel Cabinet with Baked Enamel Finish
10 Year Heat Exchanger, Flue Collector and Burner Warranty

5 Questions Answered

Description

Sterling TD Series Tubular Duct Furnace

Natural Gas, Aluminized Steel Heat Exchanger

The Sterling TD Series TD400A1NS111 is a 400,000 BTU natural gas duct furnace designed for use with existing ducted-air systems in commercial, industrial, and other large-space applications. Its tubular heat exchanger, In-Shot burner technology, direct spark ignition, and power venting deliver dependable heating, improved seasonal efficiency, and long-term durability.

Features:

400,000 BTU Heating Capacity – Delivers powerful heating for commercial and industrial ducted-air applications.
82% Thermal Efficiency – Provides efficient combustion while maximizing usable heat output.
In-Shot Burner Design – Delivers reliable combustion and consistent heating performance.
20-Gauge Steel Jacket – Baked enamel finish provides durable protection and a clean appearance.
Double-Wall Construction – Adds durability while helping protect internal components.
115V, 1-Phase, 60 Hz Power – Supports standard electrical connections for straightforward installation.
Direct Spark Ignition – Provides fast, reliable pilotless burner ignition and heat delivery.
Redundant Single-Stage Gas Valve – Provides dependable gas control for reliable operation.
115/24V Control Transformer – Supplies the appropriate low-voltage power for system controls.
Power-Vented Design – Promotes reliable exhaust performance and flexible venting installation.
20-Gauge Stainless Steel Heat Exchanger – Provides durable heat transfer and long-lasting performance.
Four-Point Suspension – Provides stable support for overhead installation.
Easy-Access Control Panel – Simplifies servicing, maintenance, and troubleshooting.
Field-Convertible Control Access – Left-hand controls can be converted to right-hand access for installation flexibility.

Aluminized Steel Heat Exchanger

Provides reliable heat transfer and corrosion resistance for clean, dry commercial and industrial applications. It offers a durable, cost-effective option for standard heating environments.

Direct Spark Ignition System

Pilotless direct spark ignition provides fast, reliable heat without a continuously burning pilot. An integrated electronic control board with an onboard LED indicator simplifies operation monitoring and troubleshooting.

Flexible Venting Options

ETL-certified Category III venting supports vertical or horizontal installation with single- or double-wall venting materials. Optional air inlet kits allow field conversion to separated combustion for dusty, dirty, humid, mildly corrosive, or slightly negative-pressure environments.

Accessible Controls

Ignition and fan controls are conveniently located in a centralized control panel for easier service and maintenance. The accessible design provides control isolation while maintaining a clean exterior appearance.

Warranty

The Sterling TD Series includes a 10-year limited warranty covering the heat exchanger, flue collector, and burner. This extended warranty coverage provides added peace of mind and confidence in the unit’s long-term durability and reliable heating performance.

Product Specs

More Information
Sterling TD Series 400,000 BTU Tubular Duct Furnace, Natural Gas, Aluminized Steel Heat Exchanger
Feature	Spec
SKU	TD400A1NS111
Weight (in lbs)	30
Brand/Manufacturer	Sterling
Furnace Efficiency / AFUE	80-85%
Heating BTU	300,000 BTU
Heat Exchanger Material	Aluminized Steel
Maximum CFM	7585
Venting Type	Power Vent or Separated Combustion
Flue Outlet	5"
Electrical	115 Volt 1 Phase 60 Hertz
Phase	Single Phase
Operating Mode	Heating
Maximum Inlet Pressure	14"wc
Ignition Type	Direct Spark Ignition
Fuel Type	Natural Gas
Height	23.5"
Width	65.5"
Depth	32.7"
Warranty	Limited 10-Year Warranty on the Heat Exchanger, Flue Collector, and Burner
Resources	Sterling Brochure Sterling Installation Manual Sterling Specification Sheet You will need Adobe® Acrobat® Reader to view PDF documents.
Safety Information	This gas appliance requires a trained technician to install. Improperly connecting gas lines or improperly connecting a gas flue or venting may result in death. By purchasing this item, you are agreeing that you are using a trained technician to install this gas appliance. We will not be responsible for any injury or property damage arising from improper service or service procedures. Whoever installs or services this unit assumes responsibility for any personal injury or property damage which may result. Many jurisdictions require a license to install this equipment. PROPOSITION 65 WARNING This product and many products on our site may contain a chemical known to the state of California to cause cancer or birth defects or other reproductive harm. For more information about Proposition 65 please Click Here.

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FAQ's

Customer Questions

What is a Sterling TD Series duct furnace?

Hello, thank you for reaching out. A Sterling TD Series duct furnace is a gas-fired heating unit that is designed to heat the air in existing HVAC systems and ducted air applications. These duct furnaces use a tubular heat exchanger and Sterling's In-Shot burner technology to provide its reliable heating for commercial and industrial spaces. The TD Series duct furnaces are available in natural gas and propane configurations and either aluminized steel or stainless steel heat exchangers. If you have additional questions, please feel free to reach out over the phone to our Customer Service line at 1-888-901-5460. Have a great rest of your day.

How do I choose the right Sterling TD duct furnace for my building?

Hello, thank you for reaching out. Choosing a Sterling TD duct furnace is based on your building's heating requirements, its existing ductwork, fuel availability, and installation conditions. The TD Series is available in seven sizes that range from 100,000 to 400,000 BTU and also in two different heat exchanger materials - aluminized steel or stainless steel. Which these options allow customers to select a heating capacity that fits their application. A qualified HVAC professional can help to determine the appropriate size, airflow and installation requirements for your space. If you have additional questions, please feel free to reach out over the phone to our Customer Service line at 1-888-901-5460. Have a great rest of your day.

What venting options are available for Sterling TD duct furnaces?

Hello, thank you for reaching out. Sterling TD Series duct furnaces are power vented and ETL certified for Category III venting requirements. These duct furnaces support vertical or horizontal venting using single-wall or double-wall venting materials. Which this flexibility can make it easier to plan an installation around existing building conditions. A qualified installer should select the correct venting materials and configuration for the specific furnace. If you have additional questions, please feel free to reach out over the phone to our Customer Service line at 1-888-901-5460. Have a great rest of your day.

How easy are Sterling TD duct furnaces to service and maintain?

Hello, thank you for reaching out. Sterling TD Series duct furnaces feature an easy-access control panel with ignition and fan controls located in one central location. This design helps to allow service technicians access important components more easily during its maintenance and troubleshooting. The control access is also field convertible from left-hand to right-hand access without requiring additional parts. If you have additional questions, please feel free to reach out over the phone to our Customer Service line at 1-888-901-5460. Have a great rest of your day.

Can Sterling TD duct furnaces be installed with existing ductwork?

Hello, thank you for reaching out. Yes, these Sterling duct furnaces are designed to be used with existing HVAC systems and ducted air applications. They can be incorporated into a ductwork system to heat and distribute air throughout a building. Before purchasing, confirm that the furnace's heating capacity, airflow requirements, physical dimensions, and installation configuration are compatible with your existing system. If you have additional questions, please feel free to reach out over the phone to our Customer Service line at 1-888-901-5460. Have a great rest of your day.