SWA

[diy-newby]

I need approx 10 ft of SWA. All the sheds / screwfix etc seem to sell a minimum of 10m. Does anyone know where I could purchase 10ft of the stuff?

[Andy Hall]

TLC Electrical.

However, they sell in metres, not the units of the ancient world.

[Andrew Gabriel]

Some wholesalers will sell the larger SWA by the metre, but I doubt they'd break into a drum of the smaller stuff, but you could ask. I once got a drum very cheaply because the drum side had broken off and they just wanted it out of the warehouse before it spewed all over the floor.

[Huge]

I have a 10ft-ish offcut. Somewhere.

Where are you?

(You ask on Freecycle?)

[Dave Plowman (News)]

TLC or another electrical wholesaler? But they will only sell by the metre.

[John Rumm]

TLC and most electrical wholesalers will sell it cut to order, either online or at one of the shops:

[diy-newby]

Thanks

[ARWadworth]

You could trick the staff by buying 3.048 metres of SWA and not telling them that it is 10 ft.

Adam

[grumpyat]

[e-mail]...

I've got 10 foot of 185mm x 4 core, you didn't say what size you wanted though!

[John Rumm]

There is a fair chance that will be "adequate" though ;-)

(I have probably got at least 10' of 4mm^2 2 core if that is any use...)

[Owain]

Might exceed the permitted conductor size of the accessory.

Owain

[grumpyat]

Sorry, my mistake. Just checked and its 240mm x 4 core. You could prob give the strands a bit of a haircut if required. Got some little crimps for it as well.

[diy-newby]

Hi,

Thanks for the offer, only need 3 core. BTW, what does the 240mm refer to? I have some rear garden wall lights and an exterior plug socket. The power is taken from a junction box on the outside of my house which feeds the garage. Whoever installed the rear lights (I have only just moved in) used normal white PVC cable from the JB to the fence. It goes underground for about 6 feet and has been hit by some workmen who installed some gates so need to replace it with SWA.

Would I need 1.5mm or 2.5mm?

[Martin Bonner]

Assuming the "240" is cross sectional area of each core, I make that about 2/3" diameter - what the **** do you connect up with that?

(If the 240 is the diameter of each core, my question still stands but I shall be expecting an answer like "power station to grid"!)

[John Rumm]

The cross sectional area of *each* conductor...

(240mm being well in excess of anything you would ever encounter in a domestic environment!)

Are you sure you need three core? (given that you can use the armour for your protective conductor (i.e. earth)

That depends on the total design load (sounds like 16A ought to be adequate in this case) and the length of the cable. When calculating voltage drop, don't forget to include the internal cable run that gets as far as your junction box (which I hope is a exterior grade waterproof one!)

All explained here:

[John Rumm]

Something that needs *lots* of current!

If it is a Ali cable then that will carry 386A per phase, or 520A per phase for a copper one. (at 90 deg C, clipped direct)

I don't have a table for anything that large!

[Andrew Gabriel]

No, it will be a few hundred kilowatts. I think that was the size of feed we had laid when we went from 600kW to 900kW supply (they always just added an extra cable for the extra, never a new cable for the lot). Eventually we got to 2MW (which required a new substation at some point), and then moved premises!

I've got a piece single core 150mm armoured here (about 1/2" diameter conductor). Being single core, the armour is copper as it mustn't be magnetic. Oh, and it's for 11,000V...

[Owain]

Electric combi boiler.

Owain

[Martin Bonner]

I think you are confused about the question I was asking. John Rumm's table gave 386A per phase for 240mm2. If we assume (invalidly) one phase, that's about 100 kW, so I think you were answering for the case where the 240 is cross sectional area.

My parenthesised question was for when the 240 is the /diameter/; which implies a cross sectional area of around 45,000 mm2.

If the maximum current is linear with the diameter then 45,000 mm2 would be good for a MW at 240V. I think the maximum current ought to grow a little faster than linear (surface area to dissipate heat is linear with diameter, but resistance falls as 1/D2 - so less heat to dissipate), Even so, it probably wouldn't be able to take a sensible power station at 240V.

Of course, that gives you a bit more power!

I remember going to the Ford Museum at Dearborn, and seeing an early factory generator. I can't remember whether it was for the Ford plant, or one of Edison's. What I do remember is that the current meter went up to 1 MA (and yes, I do have the case of that right!). You wouldn't want a one ohm junction resistance in that circuit anywhere :-)

[grumpyat]

It was just a bit left over from a server room upgrade. 240 is the csa of each core. Never heard of cable sizes relating to o.d. though. But i am often wrong [as my wife keeps reminding me]

Takes a bit of bending though