A Very Silly Question About Wires Diameters - Sorry For This

[Pawel66]

I know this is very basic, but still I decided to ask not to make a silly mistake....

In the Technical Manual we have the wire description example:

"Example: 1,5 sw/gn/rs means: 1,5 mm2 cable diameter, black cable with green and pink marking lines."

I am not sure if 1.5 is diameter or wire cross-section surface. It is either diameter (then it should be in mm) or cross section surface (then it is mm2).

Please kindly advise: what is it?

The difference is substantial if you look at it:
- starter - alternator wire has marking 4 on the diagram; if it is diameter, cross section surface is 12.56 mm2
- if 4 is the cross-section surface, then diameter would be 2.25mm (close to gauge 10)

Perhaps we can change the text in Tech Manual when it is determined what is correct.

The US Members talk e.g. 10 gauge - this is diameter (0.10 inch), as I understand.
In my place I hear electricians talk "cross section surface" most often... got lost a bit on the description we have in TM.

[WRe]

Hi Pawel,
wire specifications in electric diagrams mean wire cross sections, e.g. 1,5mm².
You can check it with following formula: Q = (π/4)*d² with d=diameter.
... Wolfgang

[Pawel66]

Wolfgang, thank you!

Cross section it is then - clear! That is what I was after.

so if someone wants to have diameter in mm (to check what is the wire in the car) while reading cross-section in mm2 from the diagram, this will be:

d=2√Q/3.14   (all of Q/3.14 is under √  I just did not know how to write it)
where
d - diameter in mm
Q - cross section mm2

Please correct me if I am wrong.

For starter- alternator wire we have
Q=4mm2 (from diagram)
then
d=2.26mm

I would suggest to look at Technical Manual and perhaps correct it. I know everybody can contribute, but I am just not qualified enough to mess with it, so I stay away...

[MikeSimon]

Myself, I am not sure that it is "cross section" and not diameter. 1.5mm² would be a rather small wire.?

[WRe]

Hi Pawel,
your formular is correct! Here you find a calculator: http://www.sengpielaudio.com/calculator-cross-section.htm.
In electric diagrams it's not usual to use diameter but cross section.
Example:
Wiring diagram shows 25 for wire from battery to starter, means 25mm² or 5,6mm diameter which is the inner metal kernel w/o coating. 25mm diameter would be rather big.
A wire with 1,5mm² has a diameter of 1,38 mm.
... Wolfgang

[Pawel66]

Wolfgang, thank you, again, for your patience and clarification - crystal clear now.

The bigger the amperage and the wire the more important this difference is, it seems.

My impression from my country was electricians always talked cross-sections (car or household). 90% of Poland's technical practices and 50% of the language comes from Germany. I thought it was cross-section, then Technical Manual said "diameter", I wanted to make sure.

[ejboyd5]

German manuals and schematics will specify wire size in terms of cross section area rather than diameter. The 1,5 mm that you reference falls between 14 and 16 gauge in the system used in the USA.  be safe and round up in size when replacing older wiring.

[66andBlue]

......and perhaps correct it. I know everybody can contribute, but I am just not qualified enough to mess with it, so I stay away...

Pawel, I am certain that you are overqualified for such a low level task. 

Anyway, it's done: https://www.sl113.org/wiki/Electrical/WiringDiagram

[Pawel66]

Alfred, thank you!

But you know how it is - one may start getting ideas, start climbing the highest mountains etc., better stay where is my place. 

I think the text modification you made will be very helpful indeed for generations to come!

[lpeterssen]

Dear Pawel

Attached a table converting cables area in mm2 to AWG numbering.

Regards
L.peterssen

[Pawel66]

Thank you!

Very useful for many of us!