![]() In still air, this particular kind of element produces 70 Watts of heat. For example, one such heating element can be adjusted using a variable-speed fan. In contrast, a conventional heating element that produces the correct amount of heat at the desired temperature will produce the same amount of heat at low temperature, resulting in long warm-up times.Ī heater with adjustable heat output can be accomplished with a PTC heating element plus a means to adjust the heat load. Such a heating element will warm up quickly, because it produces more heat at low temperatures. If the heat required to hold the desired temperature is known, a PTC heating element can be selected to provide the correct amount of heat at the desired temperature. Nevertheless, a self-regulating heating element may still be used to keep the heating element from damaging itself or other parts of the heater. In these applications, a thermostat may be better able to sense and control the temperature of the item being heated. For example, space heaters use heating elements much hotter than the room being heated. However, many applications require control of two temperatures. In some applications, where the heating element is directly connected to the item being heated, a self-regulating heater may also provide adequate temperature control of the item to be heated. One very important use of self-regulating heating elements is to assure the heating element will not become so hot as to damage itself or other parts of the heater. ![]() In some applications, this self-regulating characteristic allows PTC heaters to be used without thermostats or overtemperature protection circuits. Above that temperature, the element produces little heating power, which tends to allow it to cool. Below that temperature, the element produces a large amount of heating power, which tends to raise the temperature of the heating element. These elements are called self-regulating, because they tend to maintain that temperature, even if the applied voltage or heat load changes. Some PTC heating elements are designed to have a sharp change in resistance at a particular temperature. In comparison, most electrical heating elements also have a positive temperature coefficient, but that coefficient is so small, they produce approximately the same amount of heat regardless of temperature. ![]() ![]() PTC heating elements have a large positive temperature coefficient of resistance, which means if a constant voltage is applied, the element produces a large amount of heat when its temperature is low, and a smaller amount of heat when its temperature is high. PTC heating elements are a type of thermistor. The name self-regulating heater comes from the tendency of such heating elements to maintain a constant temperature. A positive temperature coefficient heating element (PTC heating element) or self-regulating heater is an electrical resistance heater whose resistance increases significantly with temperature. ![]()
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