AWG Sizing Question

Question

I am familiar with AWG sizing, however I need to double check on something before I go wiring it up.

I recently added a heated bed to my 3D printer which required me to upgrade to a beefier power supply. I am using a power supply that is rated for 12v 20amp output. The power supply has 3 outputs and I am currently only using two. Since my 3D printer sits in an area with less light in the room, I was thinking of using that third unused output for some lighting.

I have a decently bright USB light and a USB buck converter I want to use, but I wasn't sure of what gauge wire to use. I know the light is not going to draw a full 20 amps from the supply, so should I still be mindful of the AWG charts? If so, what gauge should I use? I am talking about, MAYBE a foot or two of wire directly between the supply and buck converter.

dougw · Accepted Answer

The wire downstream should be protected from a short at the LED load. If the wire cannot handle a dead short without melting, you should add a fuse. If you fuse it properly the wire only needs to be heavy enough to carry the LED current.

rachaelp · Answer

What Doug said is very good advice, you should definitely follow that. You can find many charts to give you the current rating based on AWG online. Be careful though there is a difference between multicore and single core wire in its rating (not much but a little) and also, if your printer is enclosed and your wire is likely to be sat in an ambient temperature significantly above room temperature you will need to derate the wire (i.e. use a larger diameter wire) for the additional ambient temperature as most of the current ratings given will be based on an ambient of around 25C for a standard room temperature.

Best Regards,

Rachael

AWG Sizing Question

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