I have a couple of lights that I am wiring right now. They have wires coming out of them that say 18AWG on them, but when I just went and bought 18 gauge wire and it is way smaller that the wires coming out of the lights. So should I go with what is written on the wire, or should I match up the physical size?
Wire size that is written on the wire or actual size?
- Thread starter JHensel
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The insulation is definitely thicker on the lights but it still seems a little different. I striped the end of the wire on the lights with the 16 gauge wire stripper, I know that isn't an exact science. Would it be better to run a wire that is a little bigger or a littler smaller than the wire coming from the light?
COMer
Well-known member
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- Aug 25, 2009
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To answer your earlier question about going with smaller or larger wire than originally used. I would definitely use the same or larger. I would not drop in size. Using #16 would create no problems. But I think the #18 is pretty normal for lights only, and you should be just fine.
Gary RV_Wizard
Site Team
AWG is actually defined only for round, solid, non-ferrous wire and represents the cross-sectional area of that wire. Stranded wire is rated as being equivalent to solid wire of a certain gauge, so stranded wire may be of a physically different diameter. What counts is the rating printed on the wire itself, since that is a result of an engineering evaluation or an actual lab test.
John From Detroit
Well-known member
Is the wire on the lights Stranded, and the wire you bought Solid? Stranded wire is physically LARGER than solid wire for the same gauge.
John From Detroit
Well-known member
Even if they are both stranded,,, there may be differences in physical size.. Somewhere, many years ago, I had to learn the math to figure out the cross sectional area.. however that was a long time ago
S
seilerbird
Guest
Stranded wire can vary in the number of stands it contains. A wire with more strands will be physically larger but if both are 18 gauge then size doesn't matter.
Kevin
Well-known member
while I'm not an expert on home wiring 
I will tell you with 12volt wiring things have changed, and not for the better. Due to rising copper cost the companies have altered their wire to save THEM money. Some have alot larger insulation with less wire, some are using alum wire as a filler, and some are just using less copper wire but still keep it the same gauge wire on the insulation jacket. Needless to say it makes my job harder to match up wire gauge with amps.
I will tell you with 12volt wiring things have changed, and not for the better. Due to rising copper cost the companies have altered their wire to save THEM money. Some have alot larger insulation with less wire, some are using alum wire as a filler, and some are just using less copper wire but still keep it the same gauge wire on the insulation jacket. Needless to say it makes my job harder to match up wire gauge with amps.
Gary RV_Wizard
Site Team
Assuming the wire manufacturer didn't lie, the gauge rating is all you need to know for basic capacity purposes. It is perfectly ok to increase a wire rating by improving the insulation jacket or using more but smaller strands or whatever. As long as it still safely carries the same current as a solid copper wire of that gauge (rated in open air), it is still legitimately that gauge.
What I think has happened, however, is a reduction in extra margin on the wires used in many applications. As Kevin notes, the high cost of copper was inspired engineers to calculate the ampacity required very closely and to specify wires with "just enough" capacity. That is bound to catch up with Do-It-Yourself modifications that do not take amp loads into account.
What I think has happened, however, is a reduction in extra margin on the wires used in many applications. As Kevin notes, the high cost of copper was inspired engineers to calculate the ampacity required very closely and to specify wires with "just enough" capacity. That is bound to catch up with Do-It-Yourself modifications that do not take amp loads into account.
