Ceramic Heater Questions

Answer: The source should be as close as practically possible to the load. However, the source should be far enough away from the load so that the infrared radiation pattern from each emitter (in a panel) will overlap each other. Some materials are very heat sensitive and if the radiant patterns of the heat source do not overlap at the load, "striping" can occur. The distance from the source to the load is dependent on the spacing between emitters. FTE emitters that are spaced 1" apart would require a distance to the load of 8" to achieve even heating of the load.

What are the radiant emission patterns of ceramic emitters?

Answer: The question often arises about the different shapes of ceramic heaters. Salamander ceramic heaters are manufactured with three basic emitter faces: convex as in the ESE, concave as in the FTE, HTE, and LTE, and flat as in the FFE, HFE and HSE. These different shapes create three different emission patterns.  Radiant energy is emitted from all objects at different levels of intensity. This energy comes off all surfaces at true right angles. The convex shape gives off a "wide area" pattern which is desired in comfort heating or other applications that require dispersed heating. A concave surface will emit a "concentrated" pattern which is highly effective when zone heating is desired as well as radiant heating in general. The flat surface will produce a "uniform" pattern for even heating at a close proximity between the emitter and the material to be heated. Examples of this are sheets of plastic or curing of surfaces.  When dealing with new applications the emission pattern needed is usually easily determined, but in retrofit applications elements should not simply be replaced without questioning whether there has been a change in application.  See page 4 of our Technical Manual for more information.

Can ceramic infrared heaters be used to heat metals?

Answer: If you apply infrared radiation to a polished metal surface, almost all of the incident infrared radiation will be reflected from the metal surface. In this condition the metal will never come up to the temperature required. The only way to effectively heat metals using infrared radiation is to increase the emissivity of the metal surface. Painting the surface of the metal will increase its surface emissivity value to 90%. Now the paint will absorb 90% of the incident infrared radiation and will transfer this heat to the metal via conduction.

Answer: On the front of all Salamander emitters there is a "Red Dragon" heat transfer. This heat transfer will turn black when the emitter is "on". When the emitter is "off" this heat transfer will return to its original red color.

Answer: Since the ceramic emitters are relatively slow responding ( 8 minute warm-up time required to achieve operating temperature ) closed loop control with an inexpensive proportional control and contactor will control the heaters typically between +/- 2 ° F. Percentage timers and SCR power controls can also be used very effectively.

A lot has been said about the zoning capability of ceramic heaters. In fact, zone control is one of the biggest advantages to using ceramic elements over other forms of infrared heaters.  Control products are available, and many are stocked at Mor Electric, and can be purchased along with the ceramic elements as well as other accessory products needed to create a "system".

The control of ceramic emitters can be one of two types: non-feedback or feedback. It is important to be able to differentiate between these two control systems in order to best advise your customers on the products available to them.

Non-feedback can control the temperature by two different methods. The first controls by time using a percentage-on/percentage-off duty cycle. When the timer is set for the on/off time cycle, the overall temperature of the emitter will stabilize. This can be done with either a mechanical timer or with a computer control.

The second method of non-feedback is through voltage control. In this application, a manual potentiometer control, or computerized control regulates the amount of voltage the emitters are receiving, thus controlling the temperature.

With Feedback control, a thermocouple is used to either measure the temperature of the element’s coil or, more accurately, the surface temperature of the element. A type K thermocouple is most universally used because of its 0-2000° F. temperature range and because it is able to be cast into the emitter where it measures the actual internal element temperature. If a Type J thermocouple is desired, in the case of low temperature applications, it must be potted into the element after firing, resulting in the measurement of the center of the emitter which is not as accurate. Mor Electric Heating Assoc., Inc. is also the only manufacturer to provide an interchangeable thermocouple in Type J or K. When inserted into a requested thermocouple well, it too will accurately measure surface temperature.

A feedback signal can also be created with a non contact infrared sensor that can sense the emitters or product temperature.

As the temperature of the element changes, the thermocouple creates a millivoltage which is sent back to a temperature controller. The controller then converts the millivoltage into a temperature reading. There are varying ranges of temperature controllers available from a simple on/off, non-indicating controller to a sophisticated digital PID control with ramp soak programming, smart tuning, etc.

Power Switching

MSI - Mercury Contactors
Featuring highly reliable, long lasting, hermetically sealed, self-renewing contacts.
120-240-480Volt
20 Amp, 35 Amp, 50 Amp, 60 Amp, 100 Amp
1 Pole, 2 Pole, 3 Pole

HBC - Solid State Relays
DIN Mount. Custom Assemblies
120-240-480Volt
20 Amp, 50 Amp, 90 Amp

Payne Engineering - SCR Controls
"2 ms" fuses protect power semiconductors against short circuits
120-240-480Volt
Phase Angle or Zero Cross Firing
10 Amps to 1200 Amps

Non-Contact Infrared Sensors

Chromalox 4-20MA or 0-5VAC Feedback
Exergen Type J or K Feedback

Non Feedback Control

Percentage Timers
Chromalox VCF & VCS Series Motor Driven Cycling
120 Volt or 240 Volt
15 second or 30 second time base
Energizes a heater for a chosen percentage (4-100%) of time base
20 Amps

Voltage Control
Infrared TYJ-6219
240 Volt, 13.5 Amps

Feedback Control
Chromalox 1600 Series High/Low Limit Controller
1/16 DIN Electronic, Digital Display
120 Volt or 240 Volt
3 Amp Relay Output or SSR Drive Output

Chromalox 2104 Series Temp. and Process Controller
1/4 DIN Electronic, PID, Digital Display
Smart Tuning / Fuzzy Logic, Ramp Soak
120 Volt or 240 Volt
8 Amp Relay, SSR Drive or 4-20 MA Output

Answer: The Salamander ceramic emitter is guaranteed for 1 year against burnout!! Typical life expectancy is in excess of 10,000 hours.

Answer: Like all infrared sources the Salamander emitter does not emit one single wavelength but a range of wavelengths. The peak wavelength emitted is dictated by the surface temperature of the emitter which can easily be controlled using closed loop or open loop control. In reference to Planck’s Law, a heater will emit a range of wavelengths which is only dependent on the surface temperature of the emitter.

Answer: As with any electrical heaters there are important warnings to consider:
Hazard of fire: Do not mount emitters/projectors near combustible materials or within a hazardous area.
Hazard of electrical shock: Disconnect power before servicing emitters or projectors. All electrical wiring must be done in accordance with local electrical codes by a qualified service technician.
Hazard of severe burns: Emitters and projectors operate at high temperatures.
Do not operate emitters at voltages in excess of rated voltage or at a surface temperature greater than 1292 °F (700 °C).

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