Knowing the difference between imperial cable and metric?

[7029 Dave]

About the only thing I've not still found in use

Last time I worked on it was the 80s, we rewired a few old big houses in Highgate London.

 

[Mike P]

The other problem with cable is when it was run in the cavity and the house then had cavity wall insulation. I have removed cable that was just copper no insulation!

 

[ExArmy]

Out of interest would you say a cable ever has a lifespan?
Let's say the imperial cable in this property is still in situ in another 50 years, and tests at 2Mohms?

Cable has a lifespan yes, but the word span just means extent of something from end to end, we don't know the maximum figure yet, it depends on external factors and how much power it's delivered in it's life. Just yesterday I did a board change and found a socket circuit wired in 7/029 with 11 sockets, evidence of a few alterations over the years, but still IR readings off the scale above 999Meg. I didn't inspect every backbox but the stuff I saw looked as good as it probably did when it was installed, likely around 20 years before I was even born.
other than green goo, and sometimes hard or brittle insulation from heat damage in the backbox from bad terminations, I've still yet to see an imperial PVC cable deteriorate like VIR does.
It's difficult to code it because you leave yourself open to "well what exactly is wrong with it, other than it's old? it still works". I might advise imperial cables be renewed when building work is done, but thats off the record and just my thoughts not something I'm putting in writing on a certificate. I don't think it would ever be a good idea to cover up old cables with insulation, plasterboard and new floor coverings as it's not worth the risk, plus the most common complaint of electrical installations that were wired in imperial cable are that there were never enough sockets by modern standards, so my advice is probably no surprise to them and they will want it rewired anyway when it's appropriate

 

[Captain Kirk]

As previously advised there was a PVC/PVC with solid strand conductor but the conductor was tinned so it was easily distinguished.

Imperial PVC/PVC copper cables became obsolete in 1970 with the introduction of the IEE Wiring Regulations - !4th Edition (Amended in metric units). - It was not BS 7671 at that time and was not a British Standard in its own right..

Obviously the use of Imperial cable would not be compliant after the re-issue as it would not comply with the BS approved cables in the new Regs, although I daresay some contractors still used any stock they had..

The original 14th edition of the IEE Wiring regulations was introduced in 1966 with imperial units only.

 

[Phoenix]

About the only thing I've not still found in use

Used to be called case and & cap I think. Worked with a guy who founnd some still in use (bearing in mind this was probably 25 years ago) and the alarm installer had decided that it made a convienient place for him to staple his 6 cores to and apparantly a good number of the staples were live

 

[Badger]

Yes but how much is still being used?

Well our whole house is wired in vir in wooden trunking from 1960's I had to search ebay for the rubber cable as it was so difficult to get hold. Off looking great especially on those old. Rewirable. Fuses in the board I'll get me

 

[7029 Dave]

Well our whole house is wired in vir in wooden trunking from 1960's I had to search ebay for the rubber cable as it was so difficult to get hold. Off looking great especially on those old. Rewirable. Fuses in the board I'll get me

I'll open the door for you