A shocking discovery

[cybergibbons]

I Have a friend that used to live in a big old country house that before mains ever came along had its own power plant. On one occasion I went into the loft and found that the lights were wired with bare copper conductors about 2.5 mm dia held on wooden and ceramic battens this had been connected as is to the mains when the rest of the house had been rewired to the standards required in the early 60's when the mains power arrived. The first thing I did was find the fuse for the circuit and remove it.

Seen this a few times before. Work of art, strung around above the ceiling. I couldn't work out the rationale behind it as the wiring down to the switches in the rooms was insulated - maybe the insulated wire was prohibitively expensive.

The copper on these ends up incredibly brittle after so many years in use. I think the cooling and heating causes work the spans to increase and decrease in tension, causing gradual work hardening. Combined with lower purity of copper than now.

[IanB]

Seen this a few times before. Work of art, strung around above the ceiling. I couldn't work out the rationale behind it as the wiring down to the switches in the rooms was insulated - maybe the insulated wire was prohibitively expensive.

Insulation was generally unreliable in the days before plastic. I think wire insulation had to be made out of rubber and protected with a woven cotton covering. The rubber could become brittle and crack with age and allow the conductors to touch inside the cable. Not good. Hence the use of insulated wires would be kept to a minimum.

With the porcelain insulators I think the idea was to keep the out and return conductors well separated so it was hard for anything to touch both at the same time. In an isolated and unearthed system touching a single wire was unlikely to create a hazard as it wouldn't complete a circuit. Porcelain and air made for a better and more reliable insulating system than a rubber sheath. (As it still does today: look at the number of power distribution systems that still use porcelain and air as the insulation mechanism.)

The copper on these ends up incredibly brittle after so many years in use. I think the cooling and heating causes work the spans to increase and decrease in tension, causing gradual work hardening. Combined with lower purity of copper than now.

Perhaps the wires should have been installed with some lack in them rather than being pulled tight. Maybe not all electricians knew about that when installing the system?

[Monkeh]

Porcelain and air made for a better and more reliable insulating system than a rubber sheath. (As it still does today: look at the number of power distribution systems that still use porcelain and air as the insulation mechanism.)

You'll find that's only for high voltage installations where insulation isn't practical. Modern materials have much higher breakdown voltages than air, the problem is you need a lot of them when dealing with tens and hundreds of kilovolts. Air is easier.

[IanB]

Air is easier.

And cheaper.

[Monkeh]

Air is easier.

And cheaper.

Precisely. It's also insane for domestic use.

[G7PSK]

Copper age hardens, also older wire had more oxygen left in during manufacture even today a lot of copper used in wire contains a lot of oxygen, I once tried using electrical wire as filler material for welding copper as I did not want to have to buy a 7KG pack just for one small job, big mistake it bubbled up like aero chocolate due to the oxygen and other gas in it had to bite the bullet and buy the correct filler wire still have most of it 15 years later.

[SeanB]

I did the same, using wire from an old transformer. Worked a charm. Now I but the correct rods and silver solder.

[IanB]

Incidentally I can attest that a 120 V shock tickles or hums a bit...

I hereby retract my words and state that this is not true. A 120 V shock bloody hurts. In the spirit of inquiry I tested what happens with dry fingers touching clean metal electrodes. If you are tempted to try that--don't! It is rather painful. 

I should note for the record that the test was done with finger and thumb of one hand and my chest was not in the current path. I may be crazy, but I am not suicidal 

[Monkeh]

Incidentally I can attest that a 120 V shock tickles or hums a bit...

I hereby retract my words and state that this is not true. A 120 V shock bloody hurts. In the spirit of inquiry I tested what happens with dry fingers touching clean metal electrodes. If you are tempted to try that--don't! It is rather painful. 

I should note for the record that the test was done with finger and thumb of one hand and my chest was not in the current path. I may be crazy, but I am not suicidal 

Now across your body, it might tickle due to the increased resistance and thus lower current. Through a hand.. even 12V hurts

Yeah, I may have grabbed one of those little lamps with 12VAC running up the telescopic arms with wet hands one day..

[Lawsen]

That outlet design and wiring are very common here in the U.S.A.  Those are single outlets in a shallow depth box for single ROMEX or solid copper cable.  You could replace it with a nonconducting, deeper plastic box.  These are available from the Home Depot.  You fortunate to have ground connector.  Many older houses and places have no ground.  American voltages are lower, 120 V AC.  I am not an electrician, but what you shown is just very common here in the U.S.A. and North America.  If you need to parallel wire another outlet, then it will need a raiser plaster metal box with an opening at the back to screw into the existing box in the wall to accommodate more wires.  I have done this before with shallow depth, tight fitting in the wall outlet box like you shown in your pictures.  These are not my favorite, but very common.