PTC Element Convection Heating
Posted by Adelle Webber on
PTC Convection Heating Improves Efficiency
New PTC ceramic heating elements improve the efficiency of typical resistive heating elements used in applications where natural convection heaters are preferable over conventional forced-air heating.
The PTC, Positive Temperature Coefficient, heating element is built into extruded aluminum profiles combining high heat capacity with low weight while not requiring additional fans to transfer heat. Aluminum profiles are designed for optimal heat transfer through a chimney effect.
Efficient Transfer of Energy
In any heating application, some form of energy, electrical, gas, oil, or even hydropower is being converted into heat. The energy of one is converted to heat energy which in turn raises the temperature of the adjoining air or physical object to bring both into equilibrium.
A PTC convection heating system converts electrical energy through the resistive element to heat which transfers very effectively to the aluminum housing. The aluminum housing is designed to radiate the heat by natural convection to the adjoining air. The heated air raises naturally and is directed to the area to be heated. The heated air then transfers the heat to the cooler surfaces until the surfaces, including human skin, reach equilibrium with the air.
Due to the compact size of these heating elements and power density, the energy transfer is more efficient than many other types of heating elements. The PTC elements draw more power initially due to lower resistance and heat faster but lower power as the element reaches equilibrium with the adjoining surface.
Temperature Control
PTC elements are valued because of the relationship between temperature and the resistance of the circuit. As the temperature increases the resistance of the circuit increases. This relationship is described as a Positive Temperature Coefficient.
More importantly, there is no risk of overheating due to the characteristics of the positive temperature coefficient PTC heaters.
Applications for PTC Convection Heating
Electrical Cabinets & Enclosures
Condensation prevention is important in cabinets and enclosures exposed to the weather and elements. The unique nature of a PTC air heater is ideal for these applications. The element adjusts heating based on ambient temperature preventing condensation from forming with temperature change. Hydrostats are often included in the circuitry to detect humidity conditions.
Vehicle Compartments
Diesel vehicle engines are slower to heat up than gasoline engines. Newer vehicles of all types are beginning to PTC convection and fan heating to rapidly heat the passenger compartments until engine heat can be utilized. 2020 Super Duty F-350 with diesel engine is an example of how PTC heating is being used for passenger comfort in cooler climates.
Electric vehicles lack the engine heat for passenger compartment heaters and are turning to electrical resistant and PTC heating elements to fill the gap. The Ford Escape has been using PTC as a supplemental heat source since 2016.
Food & Beverage Appliances
Commercial appliances used for food and beverage industries require minimum temperatures in a wide range of applications. Many can use convection PTC heating to ensure a precise set-point temperature, conserve space, and maintain safety both electrically and surface temperatures.
Benefits of PTC Convection Heating Elements
Self Regulation & Safety
PTC heating elements are temperature and current self-regulating. Each PTC ceramic element is manufactured to a specific temperature. Once the device reaches that temperature the inverse nature of the device increases resistance in the circuit to infinity effectively shutting down the circuit.
The temperature is relative to an ambient temperature such that at high ambient temperatures less current flows in the circuit to reach the set-temperature without external controls. The self-regulating nature protects the device from over-temperature and current.
Compact & Custom Sizing for Applications
Traditional heaters require space for electrical resistive heating elements and 
control circuitry often making them unsuitable for applications with limited space. PTC ceramic elements are embedded into one end of custom-sized aluminum extrusions requiring much less space and often no control circuitry.
PTC Element Efficiency
Electric heating with PTC elements is more efficient than traditional resistant heaters. The Positive Temperature Coefficient profile controls the resistance of the circuit to a specifically designed point. The warmer the element the higher the resistance. The cooler the element the lower the resistance and more current will flow increasing the heat.
These characteristics are unique in that the change in resistance and temperature is relative to ambient temperature. The higher the ambient temperature the higher the resistance will be in the circuit impeding current flow and heating the element slower.
Flexible Voltages
PTC ceramic heating elements don’t require a specific voltage to operate efficiently. AC or DC voltages work with these elements. Voltage can be specified from 12 V AC/DC - 240 V AC/DC.
Threshold Temperature
The threshold temperature for PTC heating elements is the maximum temperature that the element will reach before resistance increases and shuts off the electrical current to the device. The actual devices aren’t selected by the threshold temperature but by heating requirements of the enclosure and power required. Each device is selected based on the material and configuration of material used to transfer the heat to the surrounding surfaces.
The amount of heat required for a specific size of the cabin, enclosure, or surface area to be heated to a specific temperature determines which combination of PTC element and device is used for the application. DBK thermal heating specialist can help you select the right device and size for temperature output requirements.
High Power Density
These devices have a higher power density than resistive wire heaters. The small size of the PTC ceramic heating elements and the ability to be embedded directly into materials for efficient heat transfer results in concentrated power density.
How do you size a PTC natural convection heating element?
DBK USA has experts standing by to answer your questions. Design engineers can utilize the handing power calculator on our website. Feel free to call our thermal engineering specialists directly at 1-864-607-9047. Go to our resources page for more information on PTC convection heaters.
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