High Temperature Duct Heaters

General Description And Construction:
Glenn type ADH duct heaters are designed for easy installation in forced air ducts. Dependable Incoloy sheathed tubular elements are mounted on a heavy gauge steel mounting flange and supported by a spacer plate and four rigid support rods. Individual elements are field replaceable allowing economical maintenance to the user. Element terminals are pre-wired for a given number of heating stages. Nema I terminal covers are standard and moisture or explosion resistant housings are available. Special units can be designed to meet specific requirements.

Typical Applications:
Glenn type ADH duct heaters are suitable for processes requiring high temperature air to accomplish drying, baking, pre-heating, annealing, and similar applications. They can be used effectively when installed in forced air ducts or recirculating ovens to attain operating temperatures up to 800 deg. F. These electric units are ideal for conversion from gas or oil fired burners in existing installations.

Installation:
The heater may be bolted to the duct horizontally or vertically. If installed vertically up through the bottom of the doct, the temperature rise in the terminal cover will be minimized. Consideration should be given to the strength of the duct work required to support the weight of the heater. When necessary heaters may be ganged in tandem along the same duct work. Mounting holes are 9/32" diameter.

Wiring:
The National Electric Code and applicable local codes should be followed to bring power to the heater, fusing of the line circuit, and connection of the thermal control to the power circuit so that all heating elements are protected. Nema I enclosures are furnished with knockouts for standard 1/2" and 3/4" conduit incoming lines. Use heater only on its designed voltage, phase, and frequency. Heaters with two circuits may be wired for staged heating.

Operating Temperatures And Control:
A Glenn thermostat or temperature controller is recommended for proper control of the process and for overheat protection of the heater. Placement of thermostat bulb or thermocouple sensor should be at the top of the duct close to the heating elements, at right angles to and downstream of the air flow. Overshoot can be reduced by a setting of 50 deg. F or less than the maximum operating temperature. A pressure air flow switch to de-energize the heater is a recommended method ot precaution in the event of insufficient air flow.