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Topic Title: Aluminium wiring in former East Berlin
Topic Summary: Failure mechanisms?
Created On: 18 January 2014 12:07 PM
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 18 January 2014 12:07 PM
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stephenbiddle

Posts: 228
Joined: 18 January 2003

Hi All

My son is in a flat in former East Berlin and reports fizzing sound from socket, has been advised that it's Aluminium cable. Anyone familar with failure mechanisms of Aluminium wiring?

Thanks

Stephen
 18 January 2014 01:21 PM
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24Hour

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Yes the conductors become loose im led to belive if over tightned,

Aluminum possesses certain qualities that, compared with copper, make it an undesirable material as an electrical conductor. These qualities all lead to loose connections, where fire hazards become likely. These qualities are as follows:

higher electrical resistance. Aluminum has a high resistance to electrical current flow, which means that, given the same amperage, aluminum conductors must be of a larger diameter than would be required by copper conductors.
less ductile. Aluminum will fatigue and break down more readily when subjected to bending and other forms of abuse than copper, which is more ductile. Fatigue will cause the wire to break down internally and will increasingly resist electrical current, leading to a buildup of excessive heat.
galvanic corrosion.  In the presence of moisture, aluminum will undergo galvanic corrosion when it comes into contact with certain dissimilar metals.
oxidation. Exposure to oxygen in the air causes deterioration to the outer surface of the wire. This process is called oxidation. Aluminum wire is more easily oxidized than copper wire, and the compound formed by this process - aluminum oxide - is less conductive than copper oxide. As time passes, oxidation can deteriorate connections and present a fire hazard.  
greater malleability. Aluminum is soft and malleable, meaning it is highly sensitive to compression. After a screw has been over-tightened on aluminum wiring, for instance, the wire will continue to deform or "flow" even after the tightening has ceased. This deformation will create a loose connection and increase electrical resistance in that location.
greater thermal expansion and contraction. Even more than copper, aluminum expands and contracts with changes in temperature. Over time, this process will cause connections between the wire and the device to degrade. For this reason, aluminum wires should never be inserted into the "stab," "bayonet" or "push-in" type terminations found on the back of many light switches and outlets.
excessive vibration. Electrical current vibrates as it passes through wiring. This vibration is more extreme in aluminum than it is in copper, and, as time passes, it can cause connections to loosen.

-------------------------
Yes i do do 24/7 everyday of the FLAMIN year.
 18 January 2014 01:35 PM
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stephenbiddle

Posts: 228
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Thanks - sent that to my son, maybe that's what ended to Soviet Union
 18 January 2014 03:21 PM
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leckie

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Haven't got my regs to hand to quote but I don't think BS7671 lists aluminium conductors of less than16 sq.mm. So presumable anything less than 16sq.mm is not considered any good for the reasons given by 24hours.

There's still loads of copper clad installations around though. I think you are supposed to recommend rewiring, but you cant make someone do it can you. I wonder if you are allowed to change a consumer unit in a dwelling with copper clad cables? It would be safer than it was if rcd's are fitted.

Edited: 18 January 2014 at 03:33 PM by leckie
 18 January 2014 03:26 PM
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weirdbeard

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Originally posted by: 24Hour

Even more than copper, aluminum expands and contracts with changes in temperature. Over time, this process will cause connections between the wire and the device to degrade. For this reason, aluminum wires should never be inserted into the "stab," "bayonet" or "push-in" type terminations found on the back of many light switches and outlets.



Just a minor thought, for the reason given I would have thought aluminium conductors would be better off in spring loaded push fit connectors rather than screw connections?
 18 January 2014 03:30 PM
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KFH

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The Americans also have a problem with aluminium cable. A Google search will get you the details, 24Hour has given a very good summary. The Americans recommend rewiring or reconnecting in the back boxes with a connector approved for aluminium cable and using copper tails to the accessory.

I have a domestic customer with aluminium T&E, horrible stuff, every accessory I touch has loose connections but you have to be careful not to overtighten. I have recommended a rewire but he would not go for it as most of the house has been recently redecorated.

Edit - Wago say their connector can be used with Aluminium cables if a special paste is used to stop oxidation.
 18 January 2014 05:13 PM
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Jaymack

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Originally posted by: KFH
I have a domestic customer with aluminium T&E, horrible stuff, every accessory I touch has loose connections but you have to be careful not to overtighten. I have recommended a rewire but he would not go for it as most of the house has been recently redecorated.

Copper cores also become loose over time due to thermal cycling.

Edit - Wago say their connector can be used with Aluminium cables if a special paste is used to stop oxidation.

The paste is used to keep moisture out, Denso paste was one inhibitor, I don't know if it's still around. There is a problem due to the position on the periodic table, for relative metals such as copper and aluminium, which causes electrolytic action, i.e. a battery is formed at the joint in the presence of moisture leading to corrosion.

Regards
 20 January 2014 09:40 PM
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HarryJMacdonald

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I hope Aluminium isn't quite as bad as 24hour makes out - at least not in sizes of 16mm² and above. Most of the UK's nuclear power stations use these cables, with "squash and punch" for the termination. As regards conductivity, it does come in 3rd, after silver and copper. Over the years it has become popular and not depending on the relative price of copper and aluminium.
 20 January 2014 09:57 PM
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slittle

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The paste is still available but I can't remember the trade name at the moment.

We used it a couple of years ago when a digger decided to make a mess of a 150mm 4 core Ali cable on one of our sites


Stu
 22 January 2014 10:29 AM
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prophet

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Pirelli Biccon X1?

Had a alu cable supplying a pump house. It was the most hated but looked after cable at the firm, due to the reasons above.
 22 January 2014 02:43 PM
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Jaymack

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Originally posted by: prophet
Pirelli Biccon X1?
Had a alu cable supplying a pump house. It was the most hated but looked after cable at the firm, due to the reasons above.

There's no substitute for experience! How would it have been "looked after"?

I was a commissioning engineer, and then worked in an aluminium smelter for 6 years. Aluminium cable was installed throughout the plant, including the hollow outdoor busbars, for 275/132 kV switchyard and the MV/LV distribution etc.. The only problem occurred on commissioning a 3.3 kV motor, with a termination lug, and the wrong size of indent for an AWCO Solidal cable. If installed correctly, there's nought wrong with aluminium cable

Regards
 22 January 2014 03:35 PM
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OMS

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If installed correctly, there's nought wrong with aluminium cable


that's a big "if" though, Jaymack - I've been involved in some real dramas with aluminium conductors used in the wrong applications and installed by individuals with no real experience of terminating it properly.

It does have significantly different properties to copper (creep at normal operating temperatures being one of them) that does require what is perhaps best described as an enhanced maintenace approach and at worst is often a "heart in mouth" scenario.

Every fix that comes up to address dissimilar metals, surface oxidation, creep etc etc address some problems but in many cases also creates another problem.

I wouldn't not use aluminium but I would be very wary of it.

BTW, those busbars you mentioned did have a few problems, actually - if you look at the aluminium under a microscope, it will exhibit as a series of pyramids - so effectively it offers a point contact with much reduced surface area. Certainly, Westinghouse had significant problems with them at the generation end of the system - or did back in my supply industry days anyway

Regards

OMS

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Failure is always an option
 22 January 2014 03:44 PM
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prophet

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Originally posted by: Jaymack

Originally posted by: prophet

Pirelli Biccon X1?

Had a alu cable supplying a pump house. It was the most hated but looked after cable at the firm, due to the reasons above.


There's no substitute for experience! [IMG][/IMG] How would it have been "looked after"?



I was a commissioning engineer, and then worked in an aluminium smelter for 6 years. Aluminium cable was installed throughout the plant, including the hollow outdoor busbars, for 275/132 kV switchyard and the MV/LV distribution etc.. The only problem occurred on commissioning a 3.3 kV motor, with a termination lug, and the wrong size of indent for an AWCO Solidal cable. If installed correctly, there's nought wrong with aluminium cable



Regards


As in it was an inherited install and we monitored the terminations at the isolators with more frequency as part of our preventative maintence due to the fact it had 'burnt out' on previous occasions.

'Looked after' is merely a term of phrase :-p

Tom
 22 January 2014 05:21 PM
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OMS

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Looked after' is merely a term of phrase :-p


LoL - "nursed" might be a better one

Regards

OMS

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Failure is always an option
 22 January 2014 08:38 PM
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Jaymack

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Originally posted by: OMS
If installed correctly, there's nought wrong with aluminium cable

that's a big "if" though, Jaymack - I've been involved in some real dramas with aluminium conductors used in the wrong applications and installed by individuals with no real experience of terminating it properly.

It was in British Aluminium's interest for the reliability of the plant, to train selected electrical maintenance staff, for the installation of their proprietary AWCO cable. I spent a few days in Swansea at their rolling mill, with a couple of foremen from the smelter. I would have no hesitation in specifying it. Unfortunately now, it has a bad reputation because of incompetent installers no doubt.

It does have significantly different properties to copper (creep at normal operating temperatures being one of them) that does require what is perhaps best described as an enhanced maintenace approach and at worst is often a "heart in mouth" scenario.

I disagree with your statement about maintenance: one of the attributes of aluminium, is that it produces it's own protective layer when exposed to the air and moisture which arrests the corrosion, hence the reason why it is used for overhead busbars in switchyards and for transmission lines with a supporting steel core. As I said I had no problems with it, during a 6 year stint in a smelter; even the massive cell room busbars carrying 130 kA. in high ambient temperatures, were not a problem. Interestingly, aluminium 4" × 4" hanger rods to the consumable carbon blocks on cells, were made using friction welds to steel stubs, other joints were made using explosive charges, where the face of the aluminium was driven into steel. A fascinating industry where the metallurgists must have had a ball.

Regards
 22 January 2014 10:47 PM
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prophet

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Whilst we're on the subject, can anyone point to any literature regarding the termination of Alu? I'd be keen to have a refresher on it.

Tom
 23 January 2014 12:21 PM
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OMS

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It was in British Aluminium's interest for the reliability of the plant, to train selected electrical maintenance staff, for the installation of their proprietary AWCO cable. I spent a few days in Swansea at their rolling mill, with a couple of foremen from the smelter. I would have no hesitation in specifying it. Unfortunately now, it has a bad reputation because of incompetent installers no doubt


Indeed - as a cable it is entirely dependant on the quality of the guy terminating it. AWCO have gone now of course - the Fabien way plant is now part of a mixed use redevelopment of the former docks area

I disagree with your statement about maintenance: one of the attributes of aluminium, is that it produces it's own protective layer when exposed to the air and moisture which arrests the corrosion,


It does, although one of the issues is that it does produce a protective surface oxide quickly - so a cable being stripped back and then left over lunch before being crimped is already compromised if not brushed clean again - basically the problems as above.

I was actually talking about the creep properties being a maintenance headache - all kinds of bimetal lugs, exothermic jointing etc have not really cured the problem of the conductor material being high creep and very sensitive to bimetal corrosion.

As I said, I don't have a problem with aluminium as a conductor per se - just that I'm wary of it as it is much more sensitive to installation problems.

Regards

OMS

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Failure is always an option
 23 January 2014 01:28 PM
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AJJewsbury

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I spent a few days in Swansea at their rolling mill

Would that have been Alco/Alcoa on Jersey Marine (on the way to Baglan)? - not far from the Ford plant - if my dim memory serves? (if so, that's a blast from the past!)

- Andy.
 23 January 2014 02:22 PM
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OMS

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Originally posted by: AJJewsbury

I spent a few days in Swansea at their rolling mill


Would that have been Alco/Alcoa on Jersey Marine (on the way to Baglan)? - not far from the Ford plant - if my dim memory serves? (if so, that's a blast from the past!)

- Andy.


That's the place Andy - the manufacturing hall is now a bus museum - or so I was told.

I spent a summer placement there many years back

Regards

OMS

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Failure is always an option
 23 January 2014 02:50 PM
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AJJewsbury

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Small world! I never got inside but it was a major landmark for me in the late 1970s/ early 1980s for trips out from Swansea. I presume the "Weaver Building" has gone now too?
- Andy.
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