When is 18AWG possibly not 18AWG?

Discharged · Dec 20, 2011

I thought I had got my head around this topic - 'AWG'. I believe that means American Wire Gauge.

I bought two lots of cable earlier this year to internal wiring, but no sooner had they both arrived that I noticed the obvious difference:

DSC04656 by Tim Redberry, on Flickr

Yes, one is bigger diameter than the other - the reel says it has a diameter of 1mm, which is true. But the smaller diameter cable on the left is also lablled 18AWG. Why?

It is the one on the left that I am using for my work. It is used with 240v to power a microcontroller and to make connections on the controller. Would there be any harm in using the larger diameter cable?

As for AWG, my understanding is that the lower the number, the thicker the cable. ie, 16AWG is larger than 18AWG.

Thoughts appreciated.

Specialist · Dec 20, 2011

Is it due to different outer insulation type & thickness ?

telectrix · Dec 20, 2011

bit difficult to tell from the photo, but does 1 have thicker insulation? the AWG refers only to the conductor size, not the overall size.

Discharged · Dec 20, 2011

You know, I never thought of that. Here's the wire stripped (in haste, with a carving knife!)

DSC04657 by Tim Redberry, on Flickr

Ok, so what is the reason for the thicker insulation?

ipf · Dec 20, 2011

How long's a piece of wire?:speechless:

Specialist · Dec 20, 2011

Different insulating properties of the covering used.

Take a look at the cable section on www.cpc.co.uk & it shows the differences in insulation thicknesses.

telectrix · Dec 20, 2011

so the conductors are the same gauge, n'est pas?

Engineer54 · Dec 20, 2011

The Yanks have many types of cable, all with varying insulation thicknesses, types of insulation and heat resistance grades etc... you need to check the code type printed on the cable.

Yes the thicker/bigger the cable size, the lower the AWG figure...

Discharged · Dec 20, 2011

I don't have my Vernier gauge with me up here, but they certainly appear to be. Not something I was expecting.

GLENNSPARK · Dec 20, 2011

it may have something to do with the imperial measurments the americans still use,.....like the old BSP sizes were measured on the BORE wheres metric is on the o/d.......

Specialist · Dec 20, 2011

Discharged said:
I don't have my Vernier gauge with me up here, but they certainly appear to be. Not something I was expecting.

As they're both 18AWG, the only thing you need to think about really is: Is the insulation on both suitable for what you want to use them for ?

Engineer54 · Dec 20, 2011

So is the yank system based on O/D, and why there 3/4 and 1'' for argument's sake, is that much larger than ours conduits....

GLENNSPARK · Dec 20, 2011

well eng.....i am going by british......and british pipe sizes were on the bore......so lets say a 3/4" pipe fot instance so thats about 19mm yes.......you measure the o/d though eng.....more like just short of 22mm.........but will be sold as 3/4".......

GLENNSPARK · Dec 20, 2011

its why BSP taps and dies etc...can seem strange as they allow for the wall thickness see..........

cook1e · Dec 20, 2011

we buy a fair bit of belden and belden equivalent, when i looked into it in terms of volt drop and distance etc, i was amazed at the different metric conversions, off the top of my head it was down to 0.85 up to 1 mm, depends who you buy from seemingly. but all seems to fit the awg standard - try googling awg equivalents