SWA current capacity

[wiseingup]

I am a bit confused here when the talk is about cable size ie 4mm,10..or 16mm SWA cable does this refer to the actual cable diameter or to the cross sectional area of the current carrying wires within the SWA cable?I assume that it means that the bigger the SWA cable is the bigger the CSA and there the current capacity is greater?


Read more: //www.diynot.com/diy/threads/swa-cable-sizes.439808/#ixzz3iAcfjdiV

 

[Iggifer]

yea 1.5mm, 2.5mm 4mm, 6mm, 10mm, 16mm, 75mm etc all refer to CSA of the cores, nobody ever bothers with the 2 after mm because it's a) lots of effort to change it to the little superscript 2, and b) everyone (generally) knows what you mean.

It's pointless referring to the diameter of the cable because a) it doesn't mean anything and b) different type of cable can have the same overall diameter but different contents i.e. 2.5mm T+E is pretty much the same size as 3C 1.5mm.

 

[wiseingup]

thank you, its confirmed what I thought.

 

[EFLImpudence]

nobody ever bothers with the 2 after mm's.

That's not true.

because it's a) lots of effort to change it to the little superscript 2,

No, it isn't.

Click on the Ω sign and scroll down.
Would you have known what I meant had I not clicked on the Ω sign?

and b) everyone (generally) knows what you mean.

wiseingup understandably didn't.

It's pointless referring to the diameter of the cable because a) it doesn't mean anything and b) different type of cable can have the same overall diameter but different contents i.e. 2.5mm T+E is pretty much the same size as 3C 1.5mm.

No, it isn't.

 

[Iggifer]

nobody ever bothers with the 2 after mm's.

That's not true.

because it's a) lots of effort to change it to the little superscript 2,

No, it isn't.

Click on the Ω sign and scroll down.
Would you have known what I meant had I not clicked on the Ω sign?

and b) everyone (generally) knows what you mean.

wiseingup understandably didn't.

It's pointless referring to the diameter of the cable because a) it doesn't mean anything and b) different type of cable can have the same overall diameter but different contents i.e. 2.5mm T+E is pretty much the same size as 3C 1.5mm.

No, it isn't.

thanks.

 

[ericmark]

Cable was labelled by number of wires and diameter of each wire. So sockets were wired with 7/0.029 which means 7 cores of 0.029 inches when we went metric although the cable may have been still stranded instead of 7/0.67 the cable went to total cross sectional area so called 2.5 mm². It does make it easier as 3/036 and 7/029 were hard to work out which was the larger.

In the main I test using cable lugs. Orange = 1 mm², red = 1.5 mm², blue = 2.5 mm² and yellow = 6 mm² the latter is slack with 4 mm² and tight with 6 mm² putting a calliper or micrometer on stranded cables and converting to cross section area is not easy.

Often cable also has it printed on the plastic. However current carrying capacity is also dependent on the insulation used plastic can be thermal plastic or thermal setting and the cooling around the cable so a 2.5 mm² cable can be rated between 13.5 amp and 36 amp the latter for mineral insulated cable.

The USA as normal work in reverse to every one else and use an American wire gauge so bigger the number the smaller the wire but with the metric system the bigger the number the larger the wire.

Unfortunately DIY sheds tend to show cable with amps rating against it. Only flex which should always be exposed to free air has a fixed size to amps rating all other cables one has a chart which gives different ratings according to how used. Called the installation method. In the UK there is very little restrictions to buying and selling I can sell you an amateur radio even if you don't have a licence to use it. The DIY sheds sell items which it would be unlikely you can legally use like wood burning stoves with very low efficiency, or you can't fit yourself like gas boilers.

When I use common sizes I have a good idea of limits and often know without looking it up that it is within the limits for the job. I may also cut some corners and use expensive plug in meters which give results in seconds rather than cheaper meters and work everything out on paper. So watching any tradesman it can look a lot simpler than it really is.

So why do you want to know. School or college project or home DIY the more honest you are the more you will be told.

 

[Taylortwocities]

7/0.029 which means 7 cores of 0.029 inches when we went metric although the cable may have been still stranded instead of 7/0.67 the cable went to total cross sectional area so called 2.5 mm². It does make it easier as 3/036 and 7/029 were hard to work out which was the larger.

Eric, this is quite interesting but makes no sense unless you provide the vital missing piece of information. This mysterious 0.029inches of which you speak. Is that radius, diameter, cross sectional area, what??? After all, that's the point of the OP's question!

 

[ericmark]

Sorry imperial cable is was diameter and one could easy use a micrometer and read size direct. But it did not really help. Try and work out which has the larger current carrying capacity 3/036 or 7/029? in metric this would be 1.97 mm² and 2.98 mm² now that is instantly obvious which is bigger. OK today with PDA in my pocket maybe I could have a java script program to show this. But in the late 70's when I had both cable types with imperial and metric working out current carrying capacity of 1.97 mm², 2.5 mm² and 2.98 mm² was a real problem.

0.036 x 25.4 = 0.9144 mm divide by 2 and square it and times by 3.14159 = 0.656693 mm² time 3 = 1.970079 mm² which was the cable used for some ring finals but we also used 7 x 0.029 which using same method = 2.982987 mm² with the latter I have seen where the 2.5 mm² has melted but the 2.98 mm² showed no signs of damage where a spur had been fed off a spur many times. It seems size does matter.

 

[JohnW2]

I have seen where the 2.5 mm² has melted but the 2.98 mm² showed no signs of damage ...

If you're talking about a situation in which both were carrying the same current, I have to say that I find that rather hard to believe. ... and are you talking about 'melting' of the conductor or of the insulation/sheathing?

Kind Regards,

 

[ericmark]

Insulation melted dads house he had put many spurs onto the original 5 sockets of the ring and one had a mixture of imperial and metric and supplied at one point a 4 bar electric fire. The length of metric cable had melted at some point found when fitting RCD's but the imperial cable showed no signs of damage.

 

[JohnW2]

Insulation melted dads house he had put many spurs onto the original 5 sockets of the ring and one had a mixture of imperial and metric and supplied at one point a 4 bar electric fire. The length of metric cable had melted at some point found when fitting RCD's but the imperial cable showed no signs of damage.

What OPD did the circuit have? Are you saying that a 4-bar electric fire melted a 2.5mm² cable?

Kind Regards, John

 

[bernardgreen]

Could the mteric have been copper covered aluminium or even plain aluminium. ?

 

[JohnW2]

Could the mteric have been copper covered aluminium or even plain aluminium. ?

Who knows. However, the BS7671 CCC tables for aluminium cables conductors only start at 16mm², so I don't know what the CCC of 2.5mm² ally T+E would be. Having said that, the CCCs in BS7671 for 16mm² copper and 16mm² aluminium are very similar, so I still find it hard to believe that a 4-bar electric fire would melt a 2.5mm² aluminium cable!

Kind Regards, John

 

[wiseingup]

in answer to your Q ericmark. I have about 48M of the following SWA 2Core -7 strand cable, marked 600/1000V BS 5467. Each core when stripped of its insulation fits snuggly into a Yellow Lugg. I want to install electric into a Cabin approx. 35M away from the Main house Control box. It will be surfaced fixed with cleats to a wall all the way. The measure the CSA of each 7 stranded core is approx. 3/16" / 4.5mm Each strand of copper wire is just less than 1mm.

so my question is what will the max. current be able to be drawn from this cable? What size RCD should be installed to cover this. I would like to run a pool pump ,as well as power tools etc.

 

[Iggifer]

Does the outer sheath not say 2C 4.00mm or anything similar on it? SWA frequently has the core size printed on it.

The cable may well be up to it, but given that you are planning on installing a new circuit by the sounds of it, and don't know the size of the cable, and thus I assume don't know a) what size glands to buy or b) how to terminate the cable into these glands, you are better off getting an electrician for this job.

The other question of course is, what do you plan to do in terms of earthing the cabin?

The electrician may well be happy to use the cable you have, but that's up to him to decide