How to calculate amp draw?

[JesseS]

Here is a handy little chart that I have used for a long time for automotive use.

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[Colo_Ranger]

Here is a handy little chart that I have used for a long time for automotive use.

Thanks! The distance thing throws me. There are times I’ve used 12 gauge wire and, by the chart linked above, I should have used 8 gauge. 8 is massive and doesn’t make sense. Still trying to get a handle on it.

 

[DHMag]

Watch your inrush current. It won't be too bad with LEDs but with relays and other loads, it can play a factor. Your circuit should always be rated for 125% load.

 

[Danager]

Many of the wire gauge charts are going to account for a 3% voltage drop. Non-critical systems can experience up to 10%. While oversizing wiring can be a good idea, the best plan is to size it correctly. I’m not saying to skimp, wire incorrectly, or risk a fire. A compressor probably warrants upsizing.

Have you checked out Facebook 12 Volt Clean Wire Club? Many people there work as upfitters for emergency vehicles or on boats. They are a great resource. Just don’t buy that fancy $XXX.xx wire label maker.

BTW - here is a different version of that gauge/amp/length chart.

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