question for sparkies

Submitted: Saturday, Aug 31, 2002 at 00:00
ThreadID: 1864 Views:1828 Replies:8 FollowUps:1
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How do you measure diametar of automotive wiring? Inside or outside? Is the 6mm flexible cable the same size as 6mm flexible industrial?
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Reply By: Member - Nigel - Saturday, Aug 31, 2002 at 00:00

Saturday, Aug 31, 2002 at 00:00
I don't know how it's measured, but I believe 6mm automotive is larger than 6mm for fixed (building) wiring. The reason being DC has more loss than AC.
AnswerID: 6218

Reply By: Ray - Saturday, Aug 31, 2002 at 00:00

Saturday, Aug 31, 2002 at 00:00
Hi Crofty,

When they say 6mm they really mean 6mm squared, so this is approx 2.5mm diameter of the wire not including the insulation. As far as I know this is a measuring standard for all electrical wire however the difference between vehicle wire and home/industry fixed wire is the number of strands of wire which both reduces the risk of fatigue through constant flexing and increases surface area which improves voltage drop.

AnswerID: 6219

Reply By: Rodeoowner - Saturday, Aug 31, 2002 at 00:00

Saturday, Aug 31, 2002 at 00:00
Hey Crofty, get yourself a D1ck Smith catalogue. There are some tables in the back with the info. Cheers.
AnswerID: 6221

Reply By: Smithy - Sunday, Sep 01, 2002 at 00:00

Sunday, Sep 01, 2002 at 00:00
Household wiring is measured in what's called the cross sectional area, ( the amount of copper showing when you cut it in half ) auto wiring is measured differently. It comes in different gauges. So in answer to your question 6mm gauge auto is not the same as 6mm industrial wiring, in fact you'll find the auto wiring is larger, and more flexible.
AnswerID: 6234

Reply By: phil - Sunday, Sep 01, 2002 at 00:00

Sunday, Sep 01, 2002 at 00:00
cable is normally measured by cross sectional area. hence for instance 4mm sq cable is actually only about 2mm in diameter. good for about 32 amps. I am an electrical contractor, not sure if automotive wiring is rated the same. Should be though.
AnswerID: 6238

Reply By: Crofty - Sunday, Sep 01, 2002 at 00:00

Sunday, Sep 01, 2002 at 00:00
Thanks a lot guys. I got confused largely because i own Chescold 1180 50L fridge and manufacturer recomends 6mm wiring for it's instalation. However, when i asked for it in the store it looked too tin for my taste. It says 6mm on the rol (automotive cable) but the insulation seems to be more than 65% of the acttual cable diameter.
AnswerID: 6246

Reply By: Maurie - Friday, Sep 06, 2002 at 00:00

Friday, Sep 06, 2002 at 00:00
I am sorry to pour cold water on some of the replies but here goes. A while back I asked an auto electrician how auto cable was measured as no matter how I did the calculations I could not get 4mm for 4mm wire. His answer was that some time ago they changed the method of measuring auto wire and he didn't know how it was measured now.
I have a part roll of 4mm auto wire in front of me and the info on the label is 1 x 26/.30 (1.84sqmm). The outside diameter of the wire including insulation is about 2.8mm so where the 4mm comes from noone seems to know. As they don't have to comply with AS3000 they can label it however they like so if you are using auto cable you should get the trusty calculator out and calculate the voltage drop and see if it is acceptable for your intended use.
if anyone knows how they measure auto cable I would sure like to know.
AnswerID: 6432

Follow Up By: Les - Wednesday, Oct 02, 2002 at 00:00

Wednesday, Oct 02, 2002 at 00:00
I think this is because the diameter is only APPROX 1.84mm (not exact because of a conversion of measurement from imperial I guess).
Therefore, 1.84mm X 1.84mm (ie "squared") = 3.3856 mm or APPROX 4mm ! The reason the diameter is squared is because the whole cross section carries the current, not just the diameter---if that makes sense
4mm is very "approx" as it's actually closer to 3.5mm........
but you get that.
FollowupID: 3232

Reply By: Member - Mal - Wednesday, Sep 11, 2002 at 00:00

Wednesday, Sep 11, 2002 at 00:00
Crofty, on page 304 of the 2001-2002 D1ck Smith catalogue it has it all. It is the number of strands x the diamater of the individual strands. From this you can calculate the nominal conductor area. That means the copper you can see when you cut the wire. This is the 6mm which is really 6 square mm. It is all in a table. It even tells you how to choose a particular size wire for a certain application. Best $3.00 I ever spent. Mal Try.
AnswerID: 6534

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