Indeeco - Custom Duct Heaters
Custom Duct Heaters
Heater
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For more than 55 years, Indeeco has been supplying special heaters for use in air handling and air conditioning equipment. Indeeco has developed a wide range of special construction techniques to ensure proper operation as well as easy installation, either in the OEM’s plant or in the field. These custom duct heaters typically fall into one of the categories listed below.
Modular Construction
These heaters are designed to match adjacent AHU components, such as fans, cooling sections, filter boxes, etc. The heater mounts adjacent to other components, so it becomes simply one module of the air handling unit assembly. Unheated sections are available where there is little or no airflow, such as the area blocked by an adjacent cooling coil header. Pressure plates provide uniform airflow when the heater must be installed adjacent to the fan. Buffer sections can space the heating coils away from temperature-sensitive components or help assure uniform airflow.
Multi-Zone or Dual Duct Heaters
These custom duct heaters are for multi-zone or dual duct air conditioning equipment where the airflow is highly variable and unevenly distributed. These heaters use coils derated to approximately 25 watts per square inch (3.8 watts per square cm) of wire surface area (approximately one-half normal watt density). Low-density coils run cooler, providing longer life under these stringent operating conditions.
These heaters are supplied with fully proportional SCR control or with many heating stages to ensure that no more heat is being supplied than is absolutely necessary. Each heater stage is spread over the entire face area to take advantage of all available airflow.
A factory-installed perforated pressure plate on the air inlet side of the heater makes the airflow as uniform as possible. Linear limit thermal cutouts protect against serious overheating anywhere along the length of the heater.
Round Duct Construction
Indeeco manufactures UL-listed open coil duct heaters for installation in commercially rated round ducts. Heaters are available for installation to spiral single and double-wall or snaplock round sheet metal ducts with inside diameters from 6 to 28 inches.
Two square-to-round male galvanized steel transitions allow for field installation to the inlet and outlet of the duct heater. The transitions attach directly to the flanges of the heater and to the round duct using sheet metal screws. The Indeeco transitions are UL-approved to provide uniform airflow across the open coil elements to avoid hot spots, which could affect the performance of the heater.
Marine Duty
Only Indeeco offers a UL-listed duct heater that is also ABS-approved and meets U.S. Coast Guard requirements for shipboard use.
Variable Air Volume (VAV) Units
To serve the fast-moving and competitive VAV market, Indeeco developed a fully computerized design and construction system that enables them to quickly ship substantial volumes of heaters in a wide variety of sizes, ratings, and control options.
Some of the features for designs in this market include slip-and-drive sheet metal connections, control packages tailored to VAV systems, and special techniques for fan interlocks.
Wet, Dusty and Corrosive Areas
Indeeco offers a wide selection of custom-built electric duct heater designs for outdoor, wet, dusty, and corrosive areas. Typical applications include use with rooftop air handling equipment, washdown areas such as food processing plants, wet and humid spaces near indoor swimming pools, and marine or casino boat applications, including shipboard use.
Features:
- Disconnect switch with door interlock
- Manual reset thermal cutout
- Automatic reset thermal cutout
- Stainless steel frame
- Large diameter stainless steel finned tubular heating elements
- Heavy-duty control transformer
- Fusing per NEC
- Airflow switch
- Stainless steel terminal hardware
Outdoor UL-Listed 3R
Outdoor type 3R heaters for outdoor use provide a degree of protection against falling rain, sleet, and external ice formation. UL-listed 3R heaters are applicable in most HVAC outdoor applications and indoors for protection against dripping water. These heaters feature water-tight hubs for incoming power and control connections.
Dust-Tight Construction
A dust-tight terminal box will meet local codes that require dust-tight construction for a heater installed above a false ceiling when the entire area is used as a return air plenum. It is also suitable for commercial or light industrial applications and to avoid dust accumulation inside the terminal box while a building is under construction.
These boxes use spot-welded corrosion-resistant steel, with all openings sealed, and feature a gasketed, hinged cover and hold-down clamps. (Note that this construction does not meet the more rigid requirements of NEMA 12 described below).
NEMA 12 Type Terminal Box
For heavy-duty industrial applications involving both dust and oil, NEMA 12 construction is available on custom heaters. The all-welded, stainless steel terminal box has a hinged, gasketed cover with hold-down clamps. It also includes scru-tite hubs for line and power connections.
NEMA 4 Type Terminal Box
NEMA 4 Type construction is available for weatherproof locations and washdown areas, such as food processing plants. This all-welded stainless steel enclosure comes with a hinged, gasketed cover and water-tight hubs for incoming power and control connections.
Bottom Mounted Terminal Box
The NEC requires a workspace at least 2-1/2′ (76.2 cm) wide by 3-1/2′ (106.7 cm) deep in front of a heater terminal box for service access. More space is required for large heaters. When this space is not available at the side of a duct, install the heater through the bottom using a special bottom-mounted terminal box construction. This maintains the required horizontal orientation of open coil resistance elements.
Custom heaters of either flanged or slip-in design are available with this feature (slip-in is normally preferred for ease of installation).
Insulated Terminal Box
If a heater is in an air conditioning duct that runs through an un-airconditioned space, condensation may form inside the terminal box. To eliminate this condensation (or for energy conservation), you may request insulation at the back of the terminal box. This construction is available with all heaters.
Construction For Lined Ducts
All Indeeco slip-in heaters are suitable for use in ducts lined with up to 1″ (25.4 mm) of interior insulation. Extended terminals and the design of the thermal cutout system make standard slip-in heaters suitable for such installations without any deterioration in performance or life. Be sure that the duct dimensions specified are those inside the duct lining.