What limits the heating power output of a resistor heater?

Question

I'm a bit confused since people said those resistors would draw more power the lower its resistance is, and one way to reduce its resistance is reduce its length.

• Will it draw more power the shorter it is?
• If so, will it stop working past certain point due to temperature being too high?
• If yes, how to find the safe operating range for that heating resistor?

Currently I'm making a heater with "Nikelin" wire as a resistor heater in the form of a coil. I can't find the specification sheet for it anywhere. That "Nikelin" might be called something else in other places. All I know is that it is called that here in Indonesia. I can't even find the manufacturer. Only see it being sold in online and electronic stores.

Answer 1

Your heater specifications are as shown below.

20 AWG (2mm diameter) Nichrome wire can carry much more than 26.24 A.

15 m of wire would be required per phase to wind an air-heating element.

Answer 2

will it draw more power the shorter it is?

Yes, assuming your power supply is able to provide enough current.

if so, will it stop working past certain point due to temperature being too high?

The resistor can only get so hot before it burns or melts.

if yes, how to find the safe operating range for that heating resistor?

If nikelin is the same as nichrome wire, you need to keep the temperature below 1400 C (at every point on the wire) to avoid it melting. You could either do that experimentally (heat up some wires and see if they melt), or possibly by monitoring the resistance of the wire (which will depend on temperature).

If you want to reduce the resistance while increasing the power capability, put more resistors in parallel rather than shortening the one you have.

Answer 3

1. Don't buy anything without a datasheet unless you know exactly what to expect.

You link only translates to

Material composition resistance wire, base: iron-chromium-aluminum (FeCrAl). low resistance, magnetic.

You need 1.76 ohms (hot) per phase which can be a matrix of series and parallel resistance. The temperature rise affects reliability and also raises resistance so choose your requirements from this. Magnetic wire will also exert a force on other magnetic materials.

Wire that does not corrode can last a long time but at high temperatures the failure rate is accelerated by 2x for every 10'C rise, so choose a temperature that barely emits visible IR light for long life.

This requires more material unless this uses forced-air or liquid heat-spreading.

Beware of metal migration into a fluid and outgassing creating hot-spots.
This must be homogeneous. Stirring the medium is essential, if not critical at high heat density.

You are using 220V high voltage and expect 220V/125A = 1.76 ohms for the hot resistance on a 3 phase grid. The two variables that affect the temperature rise are the power density or W/mm^2 of surface of the wire to the surroundings and thus the resistance / m with I^2R=Power.