Method for working out the size of cable

[Tony 1]

Apologies first off as i'm sure you have answered this question many of times but really need help explaining how to work out if its a 6mm2 or 10mm2 cable. I have searched the site but cannot find the answer and i'm not understanding the term measure the cross section...

What is the calculation i need to do to work out what size the cable is?

Many thanks

 

[PrenticeBoyofDerry]

You need to know what output power the electrical equipment is.
Then divide that by the nominal voltage rating.
This will give you your current rating.
Then find a suitable sized protective device (MCB/Fuse) that can deliver this current. The next highest.
This will then help establish the CSA of the cable that can carry the current safely.
Factors such as thermal insulation, grouping cables in same routes together, ambient temps, type of fuse used and voltage drop, could also effect the cable size.

 

[Tony 1]

Thank you for but what i meant was the cable which has been installed in my old shower i'm not sure if its 6mm2 or 10mm2 and i don't know how to measure the cable to determine this as i don't know the calculation/formula

 

[ericmark]

Batt Cables under Specification give outside sizes 6mm as 6.9 x 13.4 and 10mm as 8.5 x 17.2 no guarantee all manufactures are the same but should be good indication.

 

[PrenticeBoyofDerry]

does it not have the size printed on the pvc sheath on the outer side of the cable.
Without a measurement, you can not calulate.
http://www.sengpielaudio.com/calculator-cross-section.htm

 

[Tony 1]

Thanks for the replies, no the cable has nothing on the pvc only a bs number.

 

[PrenticeBoyofDerry]

Try the link then, measure diameter of cores and it will work it out for you.
Isolate it first though

 

[1john]

if it's twin and earth then 6.0mm will have a single core 2.5mm earth, where as 10mm will have multi stranded 4mm earth in it.

 

[mikhailfaradayski]

Assuming that we are taking about T+E cable here, then:-

6mm cable has a max overall dimension of approx 13.5mm x 7mm
and
10mm cable is approx 17mm x 10mm

 

[ban-all-sheds]

In situations where you really cannot get at a conductor to measure it then fair enough, but why are so many people recommending poor alternatives like whether it has a stranded cpc, or the approximate overall dimensions of T/E, as perfectly acceptable ways to avoid doing it properly, i.e. measure the diameter of the damned thing and work it out!

 

[mikhailfaradayski]

Hi BAS,

I don't think it would be too difficult for the average person to measure the overall max. dimensions and be able to discern whether it was 6 or 10.
3.5mm difference in size is easy to see with just a ruler.

I might contend that it is easier than attempting to measure the dia of a core and then twiddling around with PI r sq'd.

Also, i wasn't suggesting anything, merely giving a bit of information which may have been some help to the OP.

 

[Taylortwocities]

For 6 and 10mm² you would need to measure a core using a micrometer,
multiply it by Πr² then times 7 as there will be seven cores.

That's the accurate method.

When faced with chosing between 6mm and 10mm, a belt and braces way is to use a 6mm and a 10mm thru crimp as a go/no go gauge.

 

[mikhailfaradayski]

I hope the micrometer would be calibrated and the measurements taken in a climate controlled environment.
Would you measure 1 core and multiply by 7, or do you think you should measure all cores?
I feel that one method may be acceptable, but other methods are the actions of desperately incompetent fools.

 

[martinxxxxxx]

The best thing to do in this situation is to call an electrician and see if he has some on his van to compare against. You never know he might be also able to give you some good advice on what cable size you actually need for the circuit you have.

The wiring of a shower is a very serious undertaking as you have high voltage, water and a wet body - this can be a dangerous mix if you are just guessing.

Good luck with your project and be safe now

Martin

 

[sparkwright]

perhaps you can find a diy shop that sells cable by the metre.

i'm sure you could smuggle out an inch long piece of both sizes.