Aluminium wiring

[Piratepete]

Hi Guys and Dolls.
I've just been asked to replace the consumer unit in a house with pvc/aluminium cored cables. - First time for me.
Current unit is the standard rewirable Wylex. The cables look in good condition though failed an overall L+N/E insulation test - until I investigate further, could be nasty or something simple such as a nightlight or extension cable with suppression.

What do I need to look out for? Also how are the cables rated? I guess theyre not 2.5/1.5 and 1.0/1.0 ?

Is there any problem clamping these wires up in modern mcb's?

Please give me your experience.
Thanks
Pete

 

[Knobhead]

If you knew how to do it you could terminate SolidAl without lugs by forming it in to a loop.
It made a really smart job.

 

[nickblake]

Article from wiki think it may be of intrest

Problems with aluminium wires
Aluminium wires have been implicated in house fires in which people have been killed.[2][3] There were several possible reasons why these connections failed. The two main reasons were improper installation and the differences in coefficient of expansion between aluminium wire and the terminations used in the 1960s.
Aluminium oxidation

Most metals (with a few exceptions, such as gold) oxidize freely when exposed to air. Aluminium oxide is not an electrical conductor, but rather an electrical insulator. Consequently, the flow of electrons through the oxide layer can be greatly impeded. However, since the oxide layer is only a few nanometers thick, the added resistance is not noticeable under most conditions. When aluminium wire is terminated properly, the mechanical connection breaks the thin, brittle layer of oxide to form an excellent electrical connection. Unless this connection is loosened, there is no way for oxygen to penetrate the connection point to form further oxide.
Coefficient of expansion

Aluminium's coefficient of expansion varies significantly from the metals common in devices, outlets, switches, and screws that were used before the mid-1970s. Many terminations of aluminium wire installed in the 1960s and 1970s continue to operate with no problems. However, many connections were not made properly when installed. Since the aluminium and steel both expand and contract at different rates under thermal load, these loose connections began to grow progressively looser over time. Likewise, a connection made with too much torque causes damage to the wire. Over time, this cycle results in the connection loosening slightly, overheating, and allowing intermetallic steel/aluminium alloying to occur between the conductor and the screw terminal. This results in a high-resistance junction, leading to additional overheating. Although many believe that oxidation was the issue, studies have shown[citation needed] that oxidation was not significant in these cases.
Joining aluminium and copper wires


Terminals joining aluminium wires to copper wires



Result improperly joined aluminium and copper wires in old USSR apartments, done by qualified electrician


Another issue is the joining of aluminium wire to copper wire. As aluminium and copper are dissimilar metals, galvanic corrosion can occur in the presence of an electrolyte and these connections can become unstable over time. Special connectors have been designed for the purpose of joining aluminium to copper wire, such as the Marrette No. 63 and No. 65 and the Ideal Twister No. 65. These twist-on wire connectors use a special antioxidant paste to prevent corrosion of the connection.
At least one manufacturer, AlumiConn, offers UL/CSA listed lug type connectors similar to those used for larger gauge aluminium-aluminium and aluminium-copper connections for branch circuit size wiring. [4] These would appear to make a more reliable connection on the aluminium wire with its higher coefficient of expansion than wire nut-type connectors. These may have the same problem with enclosure space as the COPALUM system (described under "Upgrading aluminium-wired homes"). A listed connector should always be used for connecting aluminium to copper wire.
Although aluminium wire smaller than 8 AWG is not used in new house wiring, lots of aluminium wires are used all over North America. The larger sizes offer excellent options for terminations, since the most common termination in larger sizes is a dual-rated lug made of an aluminium alloy. Properly terminated aluminium wiring should be regarded as safe, since long-term installations have proven its reliability. Aluminium wire is often used in residential applications for service entrance and large branch circuit loads such as ranges and air-conditioning units.
Hazard insurance

In some states, home hazard insurance will not cover homes with aluminium wiring, and some insurance companies that claim to cover it charge a higher premium than for homes with copper wiring. Reputable and knowledgeable insurers should recognize the difference between AA-8000 series aluminium building wire and that used prior to 1972.

 

[timo1]

This thread has been very helpful. I recently saw what I now think is tinned copper cables, the bit that threw me was it was in grey PVC sleeving. I thought the installation looked good and fairly recent (last 10 years or so) the cable on the ring seemed to be 2.5 stranded? Would it be very unlikely that the house was wired with this type of cable within the last 10 - 15 years?