70's wiring in new sockets

[crystal ball]

Yes but how did he cause a copper shortage?

 

[EddieM]

Yes but how did he cause a copper shortage?

Can only assume it was an economic decision, as copper is more expensive than ally.

 

[crystal ball]

Might be heading that way again, price of cable just sky rocketed

 

[winston1]

Cable sizes were given as 7/0.036 rather than 2.9 mm² and it was the diameter of cable not cross section area.

You mean 7/0.029. 7/0.036 did exist, that is around 4.5mm squared.

 

[SUNRAY]

I seem to remember years ago we used 2.9 mm² instead of 2.5 mm² size was reduced when we went metric, also Ian Smith caused a lack of copper at one point and we got aluminium cable for a time, the MK sockets claimed to have larger terminal holes. Cable sizes were given as 7/0.036 rather than 2.9 mm² and it was the diameter of cable not cross section area.

I remember finding in dad's house where socket feed socket etc, the 2.9 mm² into socket looked fine, but the 2.5 mm² to next socket seemed to have melted slightly so it did seem the old cable could take 30 amp where the new cable could not, although since fuse wire never sure it was 30 amp.

Although seen where ring fed lollipop fashion, to take power from the ring at centre using 4 mm² would be OK, but near the source it could cause an overload, so one would need to use an impedance meter to work out how close to centre of ring, in the same way as a double socket unfused spur is allowed but two single sockets are not, even when clearly same load, I would say taking a 4 mm² from a ring as a radial is also a bad idea, as in domestic it is rare to have a plan showing order of sockets, so it is guess work as to how close to centre unless loop impedance meter is used, and these are rather expensive and it is unlikely many DIY people have one.

In the main we use the appendix 15 plan (BS 7671:2008 regulation 433.1) to see what is permitted, and the lollipop is not show, nor is taking a supply from it with 4 mm² the regulation says I see no problem with supplying a ring final with lollipop method, using a cooker connection unit for example, but not taking a supply from the ring final as you can't ensure power sharing on the two legs of the ring.

It was never called 2.9mm², 7/0.029" happened to be 2.98mm². 7/0.036" = 4.6mm²
IIRC the official rating of 7/0.029 was something nearer to 20A and 7/0.036 was low 30's

 

[SUNRAY]

You mean 7/0.029. 7/0.036 did exist, that is around 4.5mm squared.

Thanks to Winston for a factual post.

My previous crossed in the post as I took a phone call between writing and posting

 

[ericmark]

Yes but how did he cause a copper shortage?

United Nations economic sanctions resulted in a shortage of copper. So much came from Rhodesia. Sorry showing my age.
He was in office 13 April 1964 – 1 June 1979 and we started using aluminium cables as a result.

 

[crystal ball]

So it was the UN not Smith, are you sure a lot of copper was from Rhodesia?

 

[SUNRAY]

United Nations economic sanctions resulted in a shortage of copper. So much came from Rhodesia. Sorry showing my age.
He was in office 13 April 1964 – 1 June 1979 and we started using aluminium cables as a result.

And it turned out to be a real PITA, virtually no chance of putting an ali cable back in a terminal without re-prepping and the stuff was so soft it became loose almost as soon as it was run up to near full rated current. I stripped a load out only last February.

So it was the UN not Smith, are you sure a lot of copper was from Rhodesia?

That was indeed the reason/excuse given for the Ali cable.

 

[Harry Bloomfield]

Ian Smith?

The Rhodesia embargo.

 

[ericmark]

I had problems with copper coated aluminium bus bars, to look at them you thought they were copper, but the heating and cooling would compress the bars and result in loose connections. With wagons I had start motor cables explode, and they looked the same as tinned cables but soldering them was near impossible, and crimped lugs in motor trade very unusual.

Today it is so rare we find aluminium cable except with high voltage we tend to forget about it.

 

[SUNRAY]

I had problems with copper coated aluminium bus bars, to look at them you thought they were copper, but the heating and cooling would compress the bars and result in loose connections. With wagons I had start motor cables explode, and they looked the same as tinned cables but soldering them was near impossible, and crimped lugs in motor trade very unusual.

Today it is so rare we find aluminium cable except with high voltage we tend to forget about it.

It's funny you mention the bussbars, we used miles of copper and ali and as long as the joints were made correctly they were fine, we had 2 distinct processes for Cu/Cu, Al/Al & Cu/Al however the problems with copper covered ali bars took us all by surprise and a program of identifying and replacement took place quite quickly.
I never heard what the problem was but I wondered if it was something simple like a softer compound to the solid ali bars.

My experience with ali bar is it is fine unless overloaded unlike Cu which will blue without ill effect.

 

[Harry Bloomfield]

It was never called 2.9mm², 7/0.029" happened to be 2.98mm². 7/0.036" = 4.6mm²
IIRC the official rating of 7/0.029 was something nearer to 20A and 7/0.036 was low 30's

The 0.036 was the measurement in thou's of an inch. I don't recall 7.036 ever being referred to as 2.9mm.

It was standard practise to twist the stranded 7.029 and smaller sizes neatly and tightly, to go in a terminal. The solid cores were at first twisted as before, but it was found to be better not to twist. Solid aluminium (there was only ever solid, even the big armoured cables), copper coated (except armoured), was especially brittle and easily damaged by twisting.

Flexible cables are always twisted and formed, to prevent them splaying out.

 

[crystal ball]

The Rhodesia embargo.

Yes when UDI was declared but I am not aware of Rhodesia being a major copper producer

 

[Harry Bloomfield]

It's funny you mention the bussbars, we used miles of copper and ali and as long as the joints were made correctly they were fine, we had 2 distinct processes for Cu/Cu, Al/Al & Cu/Al however the problems with copper covered ali bars took us all by surprise and a program of identifying and replacement took place quite quickly.
I never heard what the problem was but I wondered if it was something simple like a softer compound to the solid ali bars.

My experience with ali bar is it is fine unless overloaded unlike Cu which will blue without ill effect.

Maybe oxidation? Aluminium exposed to atmosphere delevelops a high resistance oxide coating. Any lugs crimped onto aluminium cables, had to be covered with a special grease prior to crimping, to prevent oxidation. I don't recall the grease being used on aluminium cables where the entered terminals, though I suspect oxidation just as much of a problem in terminals as crimps.