70s house, aluminium conductors

[Pretty Mouth]

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

Yes, all of the lighting back boxes I opened had them. Have see them a couple of times before, similar aged properties

 

[freddo]

Very common for installations with wiring or switch drops with no CPC. Insulates the plate screws from the back box.

 

[lozarus]

Very common for installations with wiring or switch drops with no CPC. Insulates the plate screws from the back box.

Yes i figured as much. In this example it could make for a nasty swap if someone were to fit a class 1 switch and not link the CPC currently terminated in the back box to new metal fitting. Interesting stuff

 

[Julie.]

Very common for installations with wiring or switch drops with no CPC. Insulates the plate screws from the back box.

Yeah, that installation looks very odd, 1mm2 was not normal, nor would be the use of twin & earth on lighting circuits in that period, also running the neutral to the switch was old-style - a sign of the use of singles just prior to using twin cable.

I would guess that it was an old electrician following the 'old' ways with the new cable of the time!

Btw, since there is a new consumer unit (mcbs or cartridge fuses) then you can up the cable rating by 133% as it's no longer course protection, but I guess you would know that

 

[Pete999]

The conductors should probably be coated with an anti-oxidant paste designed for aluminium electrical terminations. I use Ideal Noalox, though it's usually on much larger conductors.

View attachment 54887rank Mate it's not help

The conductors should probably be coated with an anti-oxidant paste designed for aluminium electrical terminations. I use Ideal Noalox, though it's usually on much larger conductors.

View attachment 54888

Are you measuring the csa….or the diameter?

Diameter I should imagine, with a micrometre as the test instrument

 

[freddo]

Your links don't work!

 

[davesparks]

Yeah, that installation looks very odd, 1mm2 was not normal, nor would be the use of twin & earth on lighting circuits in that period, also running the neutral to the switch was old-style - a sign of the use of singles just prior to using twin cable.

I would guess that it was an old electrician following the 'old' ways with the new cable of the time!

Btw, since there is a new consumer unit (mcbs or cartridge fuses) then you can up the cable rating by 133% as it's no longer course protection, but I guess you would know that

Twin cable was in use for many years before PVC insulated cable came along, TRS or lead twin was widely used much earlier than that aluminium cable was installed.

In all the old books I have read or collected on electrical installation I think I've only seen neutrals at the switches as a relatively recent method.
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Are you measuring the csa….or the diameter?

Diameter I should imagine, with a micrometre as the test instrument

The diameter is being measured and the CSA calculated from that.

The diameter appears to be 0.210mm on the micrometer (if I'm reading it right) which gives a CSA of 1.03mmsq which is within a sensible tolerance of a 1.0mmsq nominal size.

 

[Julie.]

Double post for some reason - don't know how that happened
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Twin cable was in use for many years before PVC insulated cable came along, TRS or lead twin was widely used much earlier than that aluminium cable was installed.

In all the old books I have read or collected on electrical installation I think I've only seen neutrals at the switches as a relatively recent method.
[automerge]1577481702[/automerge]

[automerge]1577482107[/automerge]



The diameter is being measured and the CSA calculated from that.

The diameter appears to be 0.210mm on the micrometer (if I'm reading it right) which gives a CSA of 1.03mmsq which is within a sensible tolerance of a 1.0mmsq nominal size.

Ok I will try again, I appeared to have double posted, then when I removed one, both disappeared???!!!

The diameter measured is 1.1mm which calculates to 0.95mm2 - so it is 1mm2

Twin and twin and earth only came into use in the late 40's, prior to this, it was single cables (double cotton /rubber covered), the practice was the live would run to the switch, then on to the next switch, with only the switch wire going to the ceiling rose, the neutral would just go rose to rose.

I think it was an old spark, continuing this idea, but with t&e ; and not someone trained with t&e, because almost straight away the three plate style of wiring came along with the new wire (rubber, and rubber/lead)

It was well before my time, but we ended up fixing/fault finding and replacing the old type wiring which was commonplace.

I think an old spark in the early 70's rewired the house following his old practices, but with the newest cable of that time - without following the associated wiring practice - He should of used twin - not twin and earth, with standard (of recent years) drop/3-plate method in 1.5mm2 (or 3/029 if really early 70's)

 

[Pretty Mouth]

Just to complicate matters, the hall and landing lights are 3 plate/ loop in at the rose (with obligatory borrowed neutral), and the bathroom is loop in at a junction box.

@Julie. , you also have a copy of the 14th ed of the regs, am.1976? I'd not heard of rewireables as being referred to as course protection before, until I saw it mentioned in the tables in it a couple of days ago. Also highly frustrating that table 24M is missing from it.

 

[Julie.]

Just to complicate matters, the hall and landing lights are 3 plate/ loop in at the rose (with obligatory borrowed neutral), and the bathroom is loop in at a junction box.

@Julie. , you also have a copy of the 14th ed of the regs, am.1976? I'd not heard of rewireables as being referred to as course protection before, until I saw it mentioned in the tables in it a couple of days ago. Also highly frustrating that table 24M is missing from it.

Yes, I have my old copy of the 14th, it is the one I started with!

Most of the guys at the time had older versions - although very few actually had the regs themselves, most had guide books - similar to the on-site guide, essentially a simpler version.

To be fair, things didn’t seam to change as much as today.

Came across loads of different ways of doing things, at college it was "this exact way or nothing" but every site we visited, you could see the evolution and mixture of practices over time