Proper wire gauges for extending all CR-10S wires

Question

I want to extend all my CR-10S wires. I have two long wire types: 22 and 18 AWG wires. I've done some research and found the following:

• Extruder heating element: 22 AWG or lower.
• Extruder thermistor sensor: 22 AWG or lower (Doesn't really need much amp).
• Fans: 24 AWG or lower (Doesn't really need much amp).
• Limit switch/filament sensor: 24 AWG or lower (Doesn't really need much amp).

Here is where I've problems determining which wire gauge to use:

• Stepper motor wires: ?
• Bed heater wires: ?

What's the wire gauge needed for the stepper motor and bed heater wires? Obviously, the bed heater needs more amp so I expect lower wire gauge. Is my 18 gauge wire enough for this?

On the Reprap site, it says that 18 AWG or lower is fine for the heating bed.

Answer 1

If my calculations are correct, a typical ceramic heating element for the extruder heating block runs 40 W. At 12 V dc, that equates to 3.33 A. A 24 awg wire is rated for 3.5 A, which means it barely covers the draw from the heater. A high torque Nema 17 motor will draw 2 A (which is probably heavier than most standard stepper motors in most 3D printing applications). Seeing as how the 18 awg wire is rated to 9.5 A, you should have no issue extending your wires using this gauge of wire for all of the extensions.

Answer 2

This answer expands on the heat bed wires question which is not addressed in this answer and gives a foundation for the edit of the question stating that AWG 18 or lower is sufficient.

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The current depends on the voltage your machine uses. The question does not state whether you modified the power supply or not. Typical values for the resistance of the bed are in the range of 1.2 - 1.8 Ω (Ohms). This implies a maximum current of $\frac{12}{1.2}=10 A$ (the stock power supply is 12 V, if the power supply is changed to 24 V, the current doubles). From this reference you can look up the ampacity (maximum current through a wire) which wire gauge fits the current for your application depending on the maximum temperature you want it to reach. For 10 Amps, you will see that AWG 18 can be used for a single wire when you allow the wire to heat up to 60 °C. Note that bundling wires lowers the ampacity of a wire, because the cooling is less optimal for bundled wires (this is called de-rating).

Please be careful when you read that certain wires are sufficient for your application. It is best to calculate the current your specific application draws from the power supply rather than relying on somebody else's calculation, it could well be that the assumptions are different than in your specific case. A multimeter or multitester is a valuable asset to aid in your calculations.