FAQ | PTC Heating
Postado por Adelle Webber em
Most Frequently Asked Questions About PTC Heating
What are PTC (positive temperature coefficient) heaters?
PTC, positive temperature coefficient, is a term used to describe the resistance characteristics of ceramic thermistor heating elements and their relationship between temperature and current flow through the device. You may also see the term positive temperature coefficient resistor (PTCR) used in scientific & manufacturing.
The term means that as the temperature of the device increases, the resistance also increases, slowing the current flow and the ceramic element's temperature increase.
The device's temperature is on the X axis on the top graph, with the resistance of the device shown with the red line on the Y axis. As the temperature increases, the resistance increases but at a logarithmic rate.
The current shown on the bottom graph on the Y axis is highest when the resistance is at the lowest point as the resistance increases with the temperature, the current decreases.
The vertical line or Te is the maximum temperature the device will reach. In most cases, the device will never reach this maximum temperature.
What is unique about PTC heating elements is that the resistance varies with ambient temperature. Suppose the ambient temperature is high. The resistance curve and resulting current start at that point. This makes the device very efficient in only producing heat needed about the surrounding temperature at lower current consumption.
What is a PTC heater?
A positive temperature coefficient (PTC) heater uses these small solid-state ceramic elements as a heat source that can be transferred to air or other materials through convection, conduction, or air movement. The heater uses aluminum fins, honeycomb matrix, or cartridge for heat transfer.
These heaters have a high watt density, are very safe, and can be used in very small spaces.
DBK USA’s Cirrus 25 fan heater is an example of a small size.
This 5,10, or 20-watt device is 1.02 X 1.06 X 1.97 inches, including the fan. It can run on 12 or 24 volts AC/DC. The 30 and 40-watt version is only slightly longer at 2.83 inches.
PTC heaters are safer than many other resistance heaters because they automatically effectively turn off the current at a specific temperature. This prevents the heater from ever overheating.
There is also no combustion to produce heat, eliminating the change of surrounding materials catching fire.
View the complete spec sheet for a small PTC Fan heater PDF here.
What is a PTC ceramic heating element?
The PTC ceramic heating element is created by compressing ceramic material doped with unique, rare earth elements into discs or squares. Electrodes are attached to the substrate layers. The difference in layers creates a resistance when current flows through the connections.
Advanced 3D manufacturing of ceramic has produced more variety of shapes and sizes, including honeycomb lattice components.
What kind of heating is PTC?
PTC is electrical resistance heating without combustion. The heating requires no oxygen or vacuum to produce its heat.
The traditional light bulb has a resistive wire element housed in a vacuum tube to prevent the element from burning out by coming into contact with oxygen.
Newer LED lights are solid-state devices similar to the PTC heating element but produce light instead of heat.
What is PTC ceramic heating technology?
The technology is similar to thermistors, diodes, and silicone control rectifiers but specially created for the positive temperature coefficient effect. The ceramic reference comes from the substrate of powdered ceramic materials molded into disc, square, or rectangular shapes and dopped with barium titanate or similar materials. The amount of material determines the maximum temperature the device will reach when the current is applied.
If you look closely at the exposed squares in the LED light of the previous photo, they will give you a reasonably good idea of what a PTC thermistor looks like.
What temperature do PTC heaters reach?
Each PTC heater has a specified temperature range. The highest temperature can be between 104 F to 392 F. Although due to the PTC characteristics, the devices never actually reach these maximum temperatures. Adjustments need to be made based on the conductivity of the heat transfer materials and the type of PTC heater to determine the actual heat produced.
Where are positive temperature coefficient heaters used?
Since their introduction in the 1980s, these small, efficient heaters have been widely used to replace traditional electrical resistive heating in home appliances and commercial and industrial applications.
What is the best device for my application?
Every heating element needs a way to transfer the heat to the surface, material, or air to be heated. The small ceramic disks are embedded in a finned, honeycomb, or cartridge structure designed to efficiently conduct the heat away from the disk to accomplish this goal.
PTC heating components are commonly classified into the following types:
- PTC Fan Heaters
- PTC Convection Heaters
- PTC Surface Heaters
- PTC Cartridge Heaters
- PTC Finned Air Heaters
More Questions and Answers on PTC Heating?
Speak directly with one of our Thermal Management Engineers for the best solution for your PTC heating needs. Call: 1-864-607-9047 Mon-Fri 8 AM - 5 PM Eastern Time.