A duct air heater is generally an assembly of tubular heating elements ready to mount into a duct but it can also be an open-coil resistance wire assembly mounted into a duct.
Finned tubular heating elements allow a max sheath temperature of 850 degF and a max airflow of 1700 FPM, while high temperature tubular heaters allow a max sheath temperature of 1500 degF and up to 2150 degF.
Most of these air heaters must have a minimum airflow. We therefore recommend the installation of airflow meters and high limit temperature sensors. The temperature sensor has normally exposed junctions and the electrical power is switched by a solid state relay (SSR) or a silicone controlled rectifier (SCR).
Typical options and features for duct heaters:
Standard pipe air heaters are rated from 800W to 6000W. Pipe heaters can withstand up to 150 PSI. The pipes are normally stainless steel. These heaters can be used to heat substances other than air, as long as the fluid is non-conductive and does not chemically react with 300 series stainless steel, silver solder, nickel, aluminum oxide or the potting material. For optimal air heater life, use solid state relay (SSR) or phase angle silicone controlled recifier (SCR) to control the power. The air temperature in the air flow can be measured with a type J or type K thermocouple with exposed junctions.
High volume inline pipe air heater:
These air heaters are intended for heating air at high flow rates (up to 60scfm) to 1000 degF maximum and features threaded inlet and outlet connections. Power required: 18kW, 240V, 3-ph, stainless steel type 304 heater shell with 2-1/2" NPT inlet and outlet. A high volume air source like a regenerative blower is usually supplying the air to the air heater.
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