[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index] Re: Correct wire sizing
Mike requests: > Is there a formula or table to choose the correct guage wire for accessories > like fog lights? Probably the best place to look is in the National Electrical Code. They are conservative and are confusing because they take wire insulation type, use, and temperature into account. You can find it in any well stocked book store. Automobile manufactures often use the smallest gauge that they can to save weight and cost. An alternative is to decide how much voltage drop you are willing to tolerate and size the wire accordingly for your current requirements. Also bear in mind that the most loss will usually occur at the connections. That is why appliance plugs often get hot, while the cord does not. Here is a quick guide for the most common sizes: AWG AMPS OHMS/1000ft Vloss = #ft*#amps*(OHMS/1000)/1000 20 2 10.35 18 5 6.510 16 10 4.094 14 15 2.575 12 20 1.619 10 30 1.081 8 45 .6405 6 60 .4028 There is some religion involved here too. Some people will use 10 gauge wire for a few amps while others don't sweat when using 14 gauge for 25 amps. Is there an SAE specification for this stuff? Most "automotive hookup wire" sold in auto parts stores has the teflon type of insulation that will tolerate the high temperatures found in a car. Don't use the PVC type or other general purpose electronic hookup wire. It won't last in the engine compartment and will melt more easily or burn in the event of a failure. Happy wiring. Don Hoefer '82 Coupe
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