Making a Coiled Heating Element from Nichrome Wire

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Discussion Overview

The discussion centers around the construction of a coiled heating element using nichrome wire, specifically addressing how coiling affects current and resistance. Participants explore theoretical and practical aspects of using nichrome in heating applications, including considerations of temperature effects and electrical properties.

Discussion Character

  • Technical explanation
  • Experimental/applied
  • Debate/contested

Main Points Raised

  • One participant questions how coiling nichrome wire will affect the current and resistance compared to straight wire.
  • Another participant suggests calculating the length of wire needed before coiling it, implying that coiling does not significantly alter the resistance.
  • A third participant adds that for typical 50/60Hz AC power, the inductance of the coil is negligible, but cautions that higher frequency applications would require consideration of inductive reactance.
  • One participant notes that coiling may retain heat, potentially increasing resistance due to surrounding temperature, but believes these effects are negligible.
  • A later reply shares an experience where the resistance of nichrome was found to remain relatively constant with temperature changes during practical use in melting aluminum.

Areas of Agreement / Disagreement

Participants express differing views on the significance of coiling on resistance and current. While some suggest that coiling does not greatly affect resistance, others raise concerns about temperature effects and inductance, indicating that the discussion remains unresolved.

Contextual Notes

There are assumptions regarding the operating frequency of the heating element and the specific conditions under which the resistance of nichrome is evaluated. The discussion does not resolve the potential impact of temperature on resistance in all scenarios.

gtg357i
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I'm making a coiled heating element from nichrome wire, and I was wondering how the coiling will affect the current. I have values for current needed for straight nichrome wire, but I believe coiling it will change the resistance.

Thanks.
 
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No, go ahead and compute your length then coil it to your needs.
 
Just to add a bit to Integral's correct response. As long as you are using 50/60Hz AC power for the coil, then the inductance of the planar coil structure is negligible for the small number of coil turns that is typical.

If you were making a 100MHz RF heating element, then you would definitely need to include the inductive reactance in your design calculations.

Do our comments that make sense and answer your question? Welcome to the PF, BTW.
 
But a coil would tend to keep the heat generated inside, instead of radiating it back to space. As a result, an increase in surrounding temperature would result in the increase of the coils resistance. But I suppose these effects would be just too negligible.

Just power the coil by a constant current source, that will take of all uncertainties.
 
The resistance of nichrome does not vary significantly with temperature. In a former job we were worried about that very thing. We cut a long, ~10m, length of nichrome measured its resistance cold, then the current and voltage drop. The resistance remains pretty constant with heating. We then calculated the heat required cut the appropriate length of wire coiled in and poured a refractory cement around the coil to create our own Aluminum melter. We melted a lot of aluminum in that very nicely, it worked as designed with no concerns about the temperature dependence of the resistance.
 

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