70s house, aluminium conductors

[Robson689]

I agree that a rewire would be for the best, hopefully they can afford it. As it stands I cannot say for certain that it has ever complied with the regulations, and I can find no data for current carrying capacity. Does anyone know if aluminium conductors would have the same CCC as copper clad aluminium conductors?

I'd imagine they have a lower capacity as aluminium has a higher resistance than copper

 

[Marvo]

Rewire the house.

Old solid aluminium conductors in domestic final circuit sizes will be a compliance nightmare with many, if not all terminations in modern electrical accessories not being suitable.

Old aluminium wiring is also a much higher fire risk in general.

If you really have to do repairs then maybe look on the USA version of ebay for bi-metallic ferrules and oxide inhibitor paste because solid aluminium house wiring was used more in the US than in the UK. If you're putting aluminium solid wire into a screw or cage termination then be aware it's as likely to fail because of overtightning as it is with undertightning.

 

[Julie.]

Copper plated aluminium and aluminium cables were all around the same, plated was ever so slightly lower, I think 1.5mm2 was 11A, and 2.5mm2 was 15A - clipped direct twin and T&E hence all the rings had to be in 4mm2 which was 19A

Only MK made fittings that were suitable - they clamped the cable and could take 2x4mm2, everything else was either too small or just used a screw - the aluminium flowed, oxidised and lost proper contact.

These were removed from the 14th in the 1976 ammendment, I think it was table 24M

But the smallest used was 1.5mm2 - I think the imperial 14th which was pre '70/72 may have had smaller cables!

As has been said, it needs a rewire, sounds like the cables have reached their end of life, once they start breaking, you will be forever repairing them!

 

[Lucien Nunes]

Agree - lighting circuits usually 1.5mm², nearest equivalent to 1.0mm² copper.
Rings 4.0mm², ditto 2.5mm² copper.

You can spot the MK fittings that were designed for aluminium because they have rising clamp terminals like DIN rail terminals or MCBs. I have some in use at home although not on Al cables; they are good terminals for any cable.

I was thinking of using this to connect a length of copper conductor to the ends of the aluminium conductors

a.k.a. 'Pigtailing' in the USA, where Al cables are much more common and this task arises more often.

Let me know if you get the rewire job. I am eager to get some good lengths of Al cable for the displays and demonstrations. I can convert it into your choice of beverage...

 

[lozarus]

Only MK made fittings that were suitable - they clamped the cable and could take 2x4mm2, everything else was either too small or just used a screw - the aluminium flowed, oxidised and lost proper contact.
!

I have an MEM type socket in use here with clamp terminals, and also have a Britmac brand single which uses the same clamp mechanism. So I suspect there were some. Competitors!

 

[Pretty Mouth]

Evening all. First, a big thank you to you all for your comments and advice, it has all been really helpful.

I went to visit the job this afternoon. When I arrived, some of the lights (downstairs circuit) weren't working at all. Tried a few switches, then some lights started flickering, then came on full. Opened up accessories and a number of conductors had broken at their terminals, several being ones I had terminated myself last visit. @Marvo , you were spot on, the aluminium conductors do not tolerate being over tightened at all.

As a temporary fix I have used Wago 773s to join the ally conductors together and 'pigtail' a length of copper to terminate in the screw terminals of the accessories. The ally wires went into the wagos easier than I expected, and continuity was apparently sound after the fix. I imagine if the Alu-plus paste was used, this could be a good fix if anyone else comes across this problem.

Before I left I quickly tested the other aluminium circuits. The cooker circuit (10mm ally) tested fine, but the ring final (4mm) had problems end-to-end; 1400ish ohms on neutral and OC on earth. I assume this has been a long term fault as the breaker has been down rated to 20A by the previous spark. I'll have to take a look it it next week.

Anyway, the good news is they want to go ahead with a rewire in February, so there will be plenty of salvaged cable for you @Lucien Nunes .
[automerge]1577474038[/automerge]
I measured the lighting conductor with a micrometer, it was indeed 1mm². A few photos:

 

[ipf]

Evening all. First, a big thank you to you all for your comments and advice, it has all been really helpful.

I went to visit the job this afternoon. When I arrived, some of the lights (downstairs circuit) weren't working at all. Tried a few switches, then some lights started flickering, then came on full. Opened up accessories and a number of conductors had broken at their terminals, several being ones I had terminated myself last visit. @Marvo , you were spot on, the aluminium conductors do not tolerate being over tightened at all.

As a temporary fix I have used Wago 773s to join the ally conductors together and 'pigtail' a length of copper to terminate in the screw terminals of the accessories. The ally wires went into the wagos easier than I expected, and continuity was apparently sound after the fix. I imagine if the Alu-plus paste was used, this could be a good fix if anyone else comes across this problem.

Before I left I quickly tested the other aluminium circuits. The cooker circuit (10mm ally) tested fine, but the ring final (4mm) had problems end-to-end; 1400ish ohms on neutral and OC on earth. I assume this has been a long term fault as the breaker has been down rated to 20A by the previous spark. I'll have to take a look it it next week.

Anyway, the good news is they want to go ahead with a rewire in February, so there will be plenty of salvaged cable for you @Lucien Nunes .
[automerge]1577474038[/automerge]
I measured the lighting conductor with a micrometer, it was indeed 1mm². A few photos:View attachment 54897View attachment 54898View attachment 54899View attachment 54900View attachment 54901View attachment 54902View attachment 54903View attachment 54904

Are you measuring the csa….or the diameter?

 

[Pretty Mouth]

Are you measuring the csa….or the diameter?

Diameter then pi X r²

 

[freddo]

Good work! Must have been quite a fragile cable to pull in, even when new. Thank goodness aluminium cable is rare in domestic installations.

 

[lozarus]

Interesting I note that the metal back boxes have plastic threads on both sides?