Non-copper wire in ring main?

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OK. It was probably well over 10 years ago when I last looked, and my recollection was that 2kW seemed to be the max available then.

Funny you should say that. One weekend I ended up working in an unheated office (warehouse sized open plan one). I was given a fan heater. On the 2kW setting, I felt nothing, but on the 1kW setting, it sent me a nice breeze of warm air. On further investigation, I realised that at 2kW, the exhaust air was hotter and didn't make it more than about 2 feet from the fan heater before just going vertically up missing me, whereas at 1kW, the air continued to move perhaps 4 feet horizontally before changing direction, so it caught me.
--
Andrew Gabriel

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R W wrote:

I am not sure. The technology was sold to and continues to be used in south africa.
The square pin is allegedly easier to make a decent high current self wiping contact with than the old round pins, and I suspect what happened was somethig like this.
(i) let's move to ring mains cos we need a LOT of sockets these days, and we can't radial wire them all, and ringing them is a bit safer and relaxes cable constraints.
(ii) let's go to a new and better type of plug.
(iii) now each appliance has its own plug, rather than one socket per room (or floor?), how much do we realistically need to rate a single point at...3KW sounds nice. Oh. Thats 13A then? Right. 13A it is...
(iv) Mmm. What will the cable stand. Ok, about 30A seems right for the sort of cable that isn't TOO heavy. Lets standardise on 30A or 32A fuses then.
(v) what about lights? Oh sod it. do them on spurs cos they are always a nightmare with cables flkying everywhere, and you seldomn need a lot of current for em. say fused at 6A - that is 12 x100w bulbs,. Thats plenty for a house.
(vi) What about all these other plugs and sockets? Oh sell em to someone who wants em. Africans will do.
(viii) I need to set up sockets for msall lamps on lighting circuits...oh well use teh 5A old style plugs if you must. At least people won't be able to plug cookers into em. and they shold take 6A before the MCB trips.
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Personally, I've only ever seen solid cored aluminium T&E. 7-stranded, if it ever existed, sounds like real recipe for aluminium connection/oxide/fire disaster.
--
Andrew Gabriel

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The old common copper house wiring sizes were 1/0.44, 3/0.29 and 7/0.29 Wonder why those sizes?
--
*You never really learn to swear until you learn to drive *

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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Ewan MacIntyre wrote:

I have seen tin-plated copper wire in some older installations; that looks silver. Are you sure its steel ? Is it magnetic ? If its silver right through, its probably aluminium, and I personally would remove every last bit I could find.
Steve
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Steve wrote:

I hadn't considered aluminium - I'll check with a magnet next time I have access to it. A good excuse to go under the floor again...
Thanks
Ewan
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Sure it's not the old 7/0.29 copper which was tin plated? Have you cut it to see if it's copper in the middle?
--
*Why can't women put on mascara with their mouth closed?

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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On Sun, 04 Jan 2004 00:34:25 +0000 (GMT), Dave Plowman

I'd suggest _not_ cutting it.
Neither should really be left in situ long-term (if you're already at the floorboard lifting stage). Aluminium, in particular, has a habit of working fine for years and then creating problems when you start to touch it - particularly if you cut it and then try to re-join it (screw terminals through a decades-old oxide layer - lovely).
It's a fair bet that it's either 7/0.29 or aluminium, but I think a definitive identification can wait until it's heading for the scrap pile.
-- Smert' spamionam
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Andy Dingley wrote:

Thanks for all the comments.
I've now investigated the layout of the ring, and it's likely that one or more of these cables will need replaced anyway, as I'm raising sockets to a proper height and so the cables are too short. I'll repost once I've cut a piece open.
Unfortunately, this same ring has my computer on it, and all our network gear. The longer the power is off, the louder the shouts are from upstairs that the broadband isn't working... ;-)
Ewan
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message <snip>

Time for rigging a temporary supply, if you know what's good for your ears (and you will be able to keep us informed as to your progress - or lack off ! :~)
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I meant at an end which was being worked on - the OP stated he was adding sockets. Sorry not to state the obvious. ;-)
--
*I don't have a solution, but I admire your problem. *

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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wrote:

I worked for a company that manufactured household wiring out of Aluminium, this could be that product, I think it was last manufactured in early 70's.
Rick
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Hello Ewan

If it bends easier than copper then it's aluminium.

Aluminium was a big test in electrical and telecomms industries a few decades ago. Not sure of the exact reasons why it's now not used, apart from a rapid degradation in salt-air conditions, but it's a common reason why adsl can't be installed and it's not used now.
--
Simon Avery, Dartmoor, UK
uk.d-i-y FAQ: http://www.diyfaq.org.uk /
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     snipped-for-privacy@digdilem.org (Simon Avery) writes:

Aluminium very quickly coats itself with a hard oxide layer which is an excellent insulator*. This can make getting a good contact area very difficult, and special techniques are required such as hard sharp contact serrations to break through the oxide and/or chemicals to remove and keep the oxide away until the contact is assembled. Add to this that if you do get a poor contact and it heats up, it rapidly gets worse, and aluminium burns (important component in fireworks), and it's a disaster waiting to happen.
Aluminium is used in the supply infrastructure, but in that case it is assembled by people who (in theory at least) know its dangers and use components specifically designed for use with it.

In telephony, the problem is mainly that of dissimilar metal corrosion, particularly in the presence of any moisture, and very much speeded up in salt-air, acids, or alkalis. BT stuff their streetside distribution points with desiccant bags in areas where aluminium wiring is used. I have one aluminium phone line, and in my experience, the connections in the streetside cabinet last around 5-6 years before they corrode through. You get about 2 weeks advance warning by seeing modem speed rapidly dropping off, before finally being completely cut off, but phoning BT and saying "my line's going to break in a week's time" just doesn't wash.
* A couple of years ago, I was breadboarding a circuit which used a couple of power MOSFETS directly switching mains. As a temporary measure, I used a bulldog clip to clamp a MOSFET to an aluminium heatsink. When I got to adding the second MOSFET into the circuit, I clamped that to the same heatsink. It was only after all the testing when I was disassembling the breadboard circuit in order to make up the real thing, that I suddenly realised that I'd had full mains voltage between the two mounting surfaces of the MOSFETS. The thin layor of aluminium oxide which inevitably forms on the heatsink was all that stopped it going bang!
--
Andrew Gabriel

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Andrew Gabriel wrote:

Yup. I done that, tho it was only 120v DC across it...

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But stranded copper 7/0.29 does bend easier than 2.5 solid - especially if rubber.
--
*Frankly, scallop, I don't give a clam

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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Ewan MacIntyre wrote:

Hi Ewan,
I shall be very surprised indeed if this is anything but tinned copper PVC covered cable. I have seen a lot of this around, and in general there's nothing wrong with it, exept that it does not conform to current standards (being multi-stranded rather than single). If the insulation is OK (not nibbled by rats etc) it should be perfectly OK for some considerable time to come.
J. --
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'Twas my understanding that it's still possible to get stranded 2.5mm singles for conduit use. And if multi-stranded cable was a no-no why is 6mm TW&E etc stranded?
--
*Do infants enjoy infancy as much as adults enjoy adultery? *

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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