Duct heaters are specialised electric heating elements designed to be installed within air ducts to provide controlled, efficient heating for various applications. They are commonly used in HVAC systems, industrial processes, and other environments requiring precise temperature management. These heaters are inserted into a rectangular opening in the duct, allowing for even heat distribution as air passes over the elements.
Stokes' modular design approach ensures flexibility, allowing a combination of standard terminal boxes and heating elements to create tailored solutions. This adaptability makes custom duct heaters ideal for both new and existing installations, accommodating unique system requirements while maintaining performance and efficiency.
Why Custom Duct Heaters Are Needed
Custom duct heaters are essential when standard heating solutions do not meet specific application needs. Some key reasons for customisation include:
- Unique Duct Dimensions: Standard heaters may not fit properly in non-standard or large-scale duct systems, requiring tailor-made inserts for optimal performance.
- Specific Heat Output Requirements: Different industries require precise wattage, voltage, and temperature controls to match their heating processes.
- Variable Airflow Conditions: Custom heaters can be designed to accommodate a wide range of airflow speeds and pressures, ensuring efficient heat transfer without overheating or energy wastage.
- Environmental Factors: Certain environments, such as high-humidity or corrosive atmospheres, require specialised materials and protective coatings to enhance durability and longevity.
- Integration with Control Systems: Many applications require heaters that integrate seamlessly with existing HVAC or industrial automation systems, including safety features such as high-limit thermostats and pressure switches.
Key Features and Options
- Modular Design: A small selection of standard components can be configured into thousands of possible heating solutions.
- High Durability: Designed to withstand vibration levels common in air conditioning and forced-air systems. Element supports prevent sagging and ensure long-term reliability.
- Optional Internal Wiring: Pre-wired options simplify installation and reduce on-site labour.
- Safety Features: High-limit thermostats and pressure switches can be incorporated for enhanced protection against overheating and airflow disruptions.
- Air Velocity Recommendations: To ensure safe and efficient operation, a minimum air velocity of 1 m/s and a maximum of 6 m/s is recommended.
Applications
- Comfort Heating: Integrated into HVAC and air conditioning systems to provide primary or supplementary heating for commercial and residential spaces.
- Forced Air Heating: Used in ventilation and process heating applications where controlled air temperature is critical.
- Process Air Heating: Suitable for industrial processes such as preheating, drying, baking, and recirculating air in manufacturing, food processing, and pharmaceutical industries.
- Specialty Applications: Can be designed for use as load or discharge resistors, blower-type unit heaters, defrost heaters, and other specialised heating systems.
Custom Manufacturing Capabilities
Stokes offers custom-built duct heater inserts with finned or unfinned elements, tailored to meet specific ratings, duct sizes, and airflow conditions. Whether an application requires a non-standard configuration, increased efficiency, or enhanced durability, our engineering team works closely with clients to design and manufacture solutions that meet their exact needs.
Installation & Order Details
Oversized Ducts
In installations where duct dimensions exceed the insert heater assembly size, the area beyond the heater could be filled with perforated or expanded metal of 50% open area. This action will maintain a uniform air velocity across the face of the duct. (fig 1.)
Bus Bar
- Slotted Brass Bus Bar
- Cat. No. U-2306-04
- The brass bar is perforated with slots 5mm x 13mm positioned centrally.
- Gap between slot 3 mm.
- Max. rating = 65 Amps., Conductor Temp. 90°C
Information Required to Order
- Duct size and entry for insert. Refer to diagram fig. 2.
- State element series to be fitted or standard specified.
- Total KW required.
- Nominate number of control steps and whether wiring is single phase or three phase.
- Airflow rate nominated.
- If you require elements pre wired with bus bar
- Nominate controls required to be fitted to assemblies, or supplied separately.
AS1668 Part 1 Australian Standards state that the following must comply.
- The casing of an electric duct heater shall be internally insulated, for a distance of not less than 250mm upstream and downstream of the heater, with a noncombustible material of thermal conductance not greater than 30W/m2 at 100°C .
- The insulation shall be secured to the casing so that it remains in position under all operating conditions.