mains cable sizing

[metalmike]

When cable described as say 2.5 T&E or 4mm, how is the size of the cable measured, ?
I asked a mate who is doing his lecky exams etc and he says he's asked but not got a straight answer.
Mike

 

[Poignard]

The cross-sectional area of each current carrying conductor is 2.5 square mm

 

[Bilgediver]

2.5 mm2 cross sectional area this is about 24 amps rating on mains

4mm is 4 mm2 maybe about 30 amps Ie for cooker

6mm 6mm2 around 45 amps showers and hobs

The americans measure diameter and use AWG

 

[VicS]

T&E stands for twin and earth. That's the cable the house is wired in not flex, that would be called 3 core.

The numbers are usually the nominal crossectional area in square mm of the conductors. Often labelled confusingly mm when it should be mm²

2.5 T&E would be the cable your ring main is wired in (2.5mm²)

Flex is often rated by its current carrying capacity eg 6A 13A etc

Sometimes the numbers relate to the construction of the conductors eg 50/0.25 indicates 50 strands of 0.25mm (diameter) wire. The equivalent crossectional area of that one is 2.5mm²

In the US, in particular, wire sizes are given in AWG American wire gauge. You would need to refer to conversion table to get the equivalent size in mm². You'll come across it in the Uk sometimes too

 

[VicS]

To continue since no has yet beaten me to it.

3A flex is 0.5mm²
6A flex is 0.75mm²
13A flex is 1.25mm²

The ratings for house wiring cable are:

1.0 mm² 10 amps for lighting circuits
1.5 mm² 15 amps for fused spurs
2.5 mm² 20 amps for ring mains
6.0mm² 35 amps for cookers or showers

ratings do depend on how the cable are run.

More info and a bit of aguide to the IEE regulations HERE

But unfortunately a bit out of date as the 17th edition was published a yer ago

 

[Gothik29]

I agree with VicS's comments, but would add one note. The 'earth' core of twin and earth is often smaller than the 'live' and 'neutral', so on a 2.5mm² twin and earth, live and neutral are 2.5mm² and the earth is 1.5mm².

Therefore if you want to use the 'earth' core for current carrying (rather than as a protective conductor), you need to take this into account.

 

[Mariner69]

OK, got the basics.

Apologies for taking over the thread but my 19 foot boat has no electrics and I hope to do a channel crossing from the Essex coast this year, so I am minded to arrange a LED tri-colour light at the masthead using a couple of small motor cycle batteries which I can throw in my bag at the end of a weekend away and charge at home. Or use a charger when alongside in a marina.

Can I get away with using the housing wire (2.5 T&E) which I have loafing in the shed?

 

[VicS]

[ QUOTE ]
Therefore if you want to use the 'earth' core for current carrying

[/ QUOTE ] But you should not be doing that even if you want to! Not only is it thinner but it is not separately insulated. When exposed it should have yellow/green sleeving fitted over it. If more cores are required, eg when wiring between two-way light switches the appropriate cable should be used, in this example 1.0mm² 3core and earth.

 

[Anthony]

[ QUOTE ]


Can I get away with using the housing wire (2.5 T&E) which I have loafing in the shed?

[/ QUOTE ]

Whilst it would work in regards that it could easily carry the current fo some nav lights its generally a bad idea to put solid cable on boats, as its less fglexibale and more prone to breaking, espically where it come outs of a connector etc with the vibration. Personally I would at least get some multistrand (e.g. flex) if you dont want to pay the extra for tinned (more corrosion resistant) cable.

Whatever you put in please make sure that the circuits are suitable fused.

Ants

 

[Strathglass]

For your application as has been said normal mains wire would be too brittle. It is also a bit overkill for feeding a led tricolour.

When I was looking for some wire for a similar task recently I found that the most cost effective solution was to use heavy duty twin loudspeaker wire from Maplin. Not tinned but quite adequate for the purpose.

Iain

 

[Mariner69]

Thank you for the advice. Will definitely use fuses.

 

[Mariner69]

Thank you for the advice. Noted the use of flex and large capacity.

Thanks all for the help.