Heat Tape Snafu - Help!

[2Biz]

I run Wintergard Wet thru my trough. No Tstat because it is self regulating.

Do you know how and what makes it self regulating? When I got mine, I plugged it in, in my house which was above 70°. It heated up....So its not like there is something inline that turns it off above freezing? Just wondering why you would want it "On" above 32°? Its using power.....Thats why I put it on a T-Stat....Maybe I'm missing something.

 

[Reds]

It is a matter of physics. You can read about it on the Raychem website. But as I understand it when the temp gets below a certain point there is a change in the conductivity of the material that is separating the 2 wires. Then the current can flow from the hot wire to the ground and generate heat. When it warms up the conductivity changes back.
The website can explain it better than I can:
"Raychem brand self-regulating heating cables consist of two parallel conductors embedded in a heating core made of conductive polymer.The core is radiation-crosslinked to ensure long-term reliability. Heat is generated as electric current passes through the conductive polymer core between the conductors. As the ambient temperature drops, the number of electrical paths through the core increases and more heat is produced. Conversely, as the temperature rises, the core has fewer electrical paths and less heat is produced."

 

[Jeff_L]

So the first conductivity probably happens above 32 degrees. If I were using it, I would put a tstat on it to measure the ambient temp. When that temp drops to 32 or less, have it supply the electricity to the tape. That way you're not burning electricity when you don't need to.

 

[Reds]

I don't recall if the conductivity starts changing at 36 or 40 degrees. But a Tstat would be a good backup to make sure it doesn't come on prematurely.

 

[2Biz]

I guess thats why I wired in the T-stat since it heated up at room temps in the 70's....