Important parameters to consider when specifying radiant heaters are maximum operating (sheath) temperature, AC voltage, kilowatts, and maximum watt density. Maximum operating temperature is the maximum temperature that the sheath covering the radiant heater may reach. Note that the maximum sheath temperature does not represent the maximum temperature that a heated substance may reach. AC voltage represents the amount of AC voltage necessary to operate the heater. Typically, the available wattage from radiant heaters is measured in kilowatts (kW). Maximum watt density is the amount of wattage, per square-inch, that a radiant heater can deliver. Watt density is calculated by dividing the available wattage by the heated area. Watt density is a good measure of the heater's ability to quickly heat a substance. High watt density heaters should not be used with extremely viscous materials, materials that are not well-circulated or explosive/volatile materials due to risk of fire.
Radiant heater differ in terms of heating element configuration and available options. Common designs include: straight, hairpin or “U” shape, sheathed tubular element, and quartz element. The most important dimension of the radiant heater is the heated length, which is also sometimes referred to as the effective length. Radiant heaters are generally available with a protective covering, or sheath. Many heaters are available with multiple sheath material options. Sheath materials for radiant heaters include aluminum, brass, copper, iron, nickel alloy, stainless steel, and steel. Radiant heaters can be installed several different ways. Mounting options for radiant heaters include sliding clamp or bracket, threat mounting bolts, or no mounting hardware.