Electronics > Projects, Designs, and Technical Stuff

Mains cable size

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ricko_uk:
Hi,
I just had someone supposedly expert insist that when someone says "1.5mm mains cable" it refers to the copper diameter because it says mm not mm^2.

That does not make any sense for two reasons: first and foremost it is the area that matters when carrying current and secondly you cannot measure the diameter of a multi stranded wire accurately because it varies depending on how much you twist the strands

But he is adamant he is right and his colleague supports his point too.

Can someone confirm that is not correct and despite the fact that in normal parlance it is say 1.5mm it is supposed to be 1.5mm^2 (i.e. square)?

Thank you

Benta:
Both of you are right (and wrong). In the EU, power cables are specified using the copper cross-sectional area. But in that case it should have the unit mm^2, sometimes you also just see a square symbol (like a box). This is true for both stranded and solid wires.
The diameter specification is used mainly in electronics for lead thickness, varnish isolated wires for coils etc. and of course has the dimension mm.

themadhippy:
Ask the "expert " to give you a bit of 2.5mm or 6mm and youll measure the results,dont accept 1.5mm as the diameter and area are pretty close

Zero999:
In the UK, mains cables are specified in mm2 but many electricians don't bother mentioning the square bit. I once asked for some 1.5mm square heat resistant cable, in an electrical shop and they said they don't have any square cable, but only round. I laughed to myself and siad "That will do, thanks." :-DD I didn't have the time to get into a discussion. I just wanted some cable for my parent's 3kW emersion heater, as the gas boiler had stopped working and the pillock who rewired the airing cupboard had taken the socket out, so I had to run a cable to the nearest outlet.

My advice is, point them to the correct information. If they still won't accept it, move on. Choose your battles.

An explaination of cable sizes and crossectional area.
https://www.diydoctor.org.uk/projects/cablesizes.htm

Note how mains cables in RS and similar UK suppliers, are specified in mm2
https://uk.rs-online.com/web/c/cables-wires/electrical-power-industrial-cable/lighting-electrical-cable/

In the UK most electrical cables are specified in sizes listed by IEC 60228.
https://en.wikipedia.org/wiki/IEC_60228

Although we also use 1.25mm2 for flexible cables on 13A plugs. Presumably this is because it's rated to 13A and cheaper than 1.5mm2, which has a 15A rating and is overkill for mains appliances with a 13A plug.
https://www.diynot.com/pages/el/el004.php

TimFox:
In another thread, I mentioned my confusion on temporary duty in UK where the local guy said "mils", meaning "millimeters", when he really meant "mm2".  I knew he didn't mean "mils", as in the American usage of 0.001 inch for diameter, and luckily the cable did not overheat (there is a noticeable difference between 6 mm diameter and 6 mm2 area).  I have been accused of being a stickler for language, but proper usage is important in technical applications.

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