Bunched 2.5mm2 Swa 4core for garage supply.

[ban-all-sheds]

Urm, 2x 2.5mm cores does not equal a 5mm core, its far less than that......

No, but 2 x 2.5mm² does equal 1 x 5mm²

If the OP did actually mean he had 2.5mm diameter cores he'd probably have 6mm² cable, or an old imperial 7/.036.

 

[phatboy]

Urm, 2x 2.5mm cores does not equal a 5mm core, its far less than that......

No, but 2 x 2.5mm² does equal 1 x 5mm²

If the OP did actually mean he had 2.5mm diameter cores he'd probably have 6mm² cable, or an old imperial 7/.036.

OK maybe I am confused then. I thought 2x 2.5mm² cores would equal approx. a 2.5 x 5mm² core, so half of a 5mm² core? Happy to be corrected.......

 

[EFLImpudence]

OK maybe I am confused then. I thought 2x 2.5mm² cores would equal approx. a 2.5 x 5mm² core, so half of a 5mm² core? Happy to be corrected.......

I would correct you but what does it mean?

Oh yes - you cannot equal approx.

 

[phatboy]

OK maybe I am confused then. I thought 2x 2.5mm² cores would equal approx. a 2.5 x 5mm² core, so half of a 5mm² core? Happy to be corrected.......

I would correct you but what does it mean?

Oh yes - you cannot equal approx.

Your attitude is not helpful. If you are going to reply please make it something constructive.

 

[Monkeh]

OK maybe I am confused then. I thought 2x 2.5mm² cores would equal approx. a 2.5 x 5mm² core, so half of a 5mm² core? Happy to be corrected.......

I would correct you but what does it mean?

Oh yes - you cannot equal approx.

Your attitude is not helpful. If you are going to reply please make it something constructive.

If you take two 1m² tiles and lay them side by side, what area do they cover?

 

[phatboy]

OK, makes sense now! Not sure where my head was at!!!

 

[Shorty73]

Urm, 2x 2.5mm cores does not equal a 5mm core, its far less than that......

No, but 2 x 2.5mm² does equal 1 x 5mm²

If the OP did actually mean he had 2.5mm diameter cores he'd probably have 6mm² cable, or an old imperial 7/.036.

Just to clarify, I have a length of SWA which contains 4 cores, each of which measures 2.5mm2 cross sectional area.

Also I have no intention of botching anything. If I did I would just run the cable regardless. I want to carry out a proper job to a good standard. I have no doubt in my skills and abilities.

The analogy of placing two tiles of equal size is not quite correct. If you were to unwind the strands of two 2.5 conductors and then rewind them into 1 conductor then the cross sectional area should equal 5mm. If I had two dustbin lids each of which covered a metre square then between them they cover 2 square meters.

 

[Monkeh]

The analogy of placing two tiles of equal size is not quite correct. If you were to unwind the strands of two 2.5 conductors and then rewind them into 1 conductor then the cross sectional area should equal 5mm. If I had two dustbin lids each of which covered a metre square then between them they cover 2 square meters.

...

So I wasn't quite correct, but I was exactly correct?

 

[Shorty73]

I will be installing 3 internal double 13a sockets and 1 external double socket. I will have two fluorescent light fittings and one outside LED light on a PIR. I may fit some heaters on a frost protection stat. As mentioned above 2.5 mm wouldn't give me much so I was intending to use the 4 core as a single phase with bunched or paired cores and either run a separate 6 mm conductor or use the steel wire conductors as the earth.

Everything really depends upon what loads you intend to plug into those 4 double sockets. There is no immediately available figure for the current-carrying capacity of 5.0mm² SWA (2x2.5mm², doubled up), since CCC is not directly proportional to conductor CSA, but it will presumably be at least as high as 2-core 4mm² SWA, which would allow you 43A if buried. With only 10-12 metres, voltage drop is not likely to be a limiting factor. What is going to be feeding this cable, and what arrangements for RCD protection of the garage circuits will you have?

The armour of the SWA would probably be adequate to act as CPC for the "5mm²" cable, but if you have a requirement for main protective bonding in the garage, you may well need to run a 10mm² cable (from house Main Earthing Terminal to garage) for that purpose. How do you intend to deal with earthing arrangements (and bonding if required) in the garage?

Kind Regards, John

John,

I will be feeding the SWA via an appropriately rated RCBO from the house C.U. And installing it in to a Garage C.U. with a 63A RCD with a 16A and a 6A MCB's.

As for load, I have no plans to fill every socket but I want the flexibility of numerous outlets. I understand diversity but also realise that if you have sockets then there's a good chance they will get filled!

I just need a robust supply that I won't be in need of upgrading any time soon. I spend my days overlaying cable or reconductoring Overhead Line which is inadequate for the load required from it due the increase in customer demands.

 

[Shorty73]

The analogy of placing two tiles of equal size is not quite correct. If you were to unwind the strands of two 2.5 conductors and then rewind them into 1 conductor then the cross sectional area should equal 5mm. If I had two dustbin lids each of which covered a metre square then between them they cover 2 square meters.

...

So I wasn't quite correct, but I was exactly correct?

My apologies!!

My heads a bit frazzled after chasing an Arc Suppression Fault in the pouring rain and then trying to find a HV earth fault which broke down at 8kv but we cannot find!! Went to work at 7 this morning and rolled in at 11 tonight!!

Re read your post saw we were on the same page.

 

[Monkeh]

The analogy of placing two tiles of equal size is not quite correct. If you were to unwind the strands of two 2.5 conductors and then rewind them into 1 conductor then the cross sectional area should equal 5mm. If I had two dustbin lids each of which covered a metre square then between them they cover 2 square meters.

...

So I wasn't quite correct, but I was exactly correct?

My apologies!!

My heads a bit frazzled after chasing an Arc Suppression Fault in the pouring rain and then trying to find a HV earth fault which broke down at 8kv but we cannot find!! Went to work at 7 this morning and rolled in at 11 tonight!!

Re read your post saw we were on the same page.

There's a lot of that going around in this thread, no worries.

 

[ban-all-sheds]

OK maybe I am confused then. I thought 2x 2.5mm² cores would equal approx. a 2.5 x 5mm² core, so half of a 5mm² core? Happy to be corrected.......

I would correct you but what does it mean?

Oh yes - you cannot equal approx.

Your attitude is not helpful. If you are going to reply please make it something constructive.

I have a great deal of sympathy with him. Apart from being picky about "equal approximately" vs "approximately equal", I agree that what you wrote made no sense at all, so much so that I couldn't even try and guess what you might have meant.

Let's simplify it, because the maths should work no matter what the object. So changing "mm² cores" to "bananas", you wrote

I thought 2x 2.5 bananas would equal approx. 2.5 x 5 bananas, so half of 5 bananas.

Do you see the problem?

 

[Monkeh]

I think the confusion is related to the fact that doubling cross sectional area does not double current carrying capacity (surface area, skin effect, yadayada).

Brain not in gear syndrome.

 

[ban-all-sheds]

I think the confusion is related to the fact that doubling cross sectional area does not double current carrying capacity

Nobody has said it does

(surface area, skin effect, yadayada).

No skin effect at 50Hz.

Brain not in gear syndrome.

If you say so.

 

[Monkeh]

I think the confusion is related to the fact that doubling cross sectional area does not double current carrying capacity

Nobody has said it does

No, but I can see how someone who's not really thinking about it could end up a bit confused if they're used to knowing that it doesn't.

(surface area, skin effect, yadayada).

No skin effect at 50Hz.

Wrong. It's not nearly as significant as at higher frequencies (obviously..), but it still exists at 50Hz.

Having checked the numbers, it's not present at 50Hz until you start using conductors with a radius upwards of 9mm, though. So not a problem with domestic size stuff.