There are very simple rules guiding on the wire size:
- A higher section area (bigger wire) will have less resistance per unit of length
- The lesser the resistance, the lesser the losses
- The lesser losses, the lesser the temperature increase
Based on your wire material, a higher temperature can be tolerated. However, for a general consumer electronic device such as a 3D printer, you don’t want to keep your wires too hot. Considering heat and convection cooling from the wires can get complicated quickly.
As a general rule of thumb, a value ranging from 1% up to 3% can be used as the losses in a wire.
Taking our previous example, our 48W heater could use a cable with a loss ranging from 0.48W up to 1.44W.
Considering a loss of 0.48W (1%) over 1 meter of wire, the sizes shown in the table below should be used.