The principle of operation of the heating cable with self-regulation of temperature
It is known to many self-regulating heating cable for heating communications: water pipes and sewers, gutters and roof elements, terraces.
But not all is known for its principle of operation and the power consumption of the cable at different temperatures.
At first, the principle of work. This cable is a two brass lived (two pins), but it is not a current flows. This is not a resistive load. They just are energized. Between these contacts is the semiconductor polymer. In its structure is graphite. Here on the polymer strands of honey and a current flows, and the polymer is heated. All of this is in the insulation and metal sheath, which can serve as a ground.
Depending on the temperature, this polymer on its various portions has a different resistance. Those. cable can be heated in different ways in these different areas. And, heating, begins to consume less power, since grows its resistance.
Brief consumption of the device and a self-regulating heating cable.
In the heated state the cable anyway consumption (about one third to one half of its nominal capacity). Keep this in mind.
The cost of the heating cable with the purchase of meters and ready-made kit.
Photo sets. There are heating cables, which can be laid inside pipes. For these purposes, they are sold with a flange. For example, for laying sewer pipes in (a common problem). Either inside the water pipes - such coatings have their food polyethylene.
The cable fixed on the plastic ties or a tape with metalized coating
For me it is not clear why some pipe wrapped with this heating cable, thereby increasing the consumption of cable per meter of pipe n? If the pipe is in thermal insulation shell, it will increase the area of the heated surface of the pipe. But. If you run a cable from the bottom of the pipe the hot air and the heat transfer through the material of the pipe will be heated its entire volume. I see no reason to heat the sewer pipe to 50 degrees (with account of heat losses). This will lead to increased levels of bacteria and odor.
Ideally, all should be considered. To do this, you need to know the values of temperatures and pressures in different environments. The experimental values for the heating cable with a power of 30 W / m can be obtained from the information in this sequence:
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Photos taken from public sources, with Yandex service. Pictures
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