Old installations with one earth for all circuits.

[th_walking_dude]

Hi All

I was just hoping someone could give me some advice on old installations (guessing 1950s and before) where a bare earth wire runs from point to point alongside normal 2 core cable.

I've come across this twice now. One time whilst ripping it out for a rewire.

I guess the practical ramifications are that at the very least it makes any future additions to circuits as good as impossible. Especially when you factor in the ancient fuse boxes these cables invariably run back to!

Then there is the age is a factor on it's own. One of the properties I have seen this in had the old thick rubber cables in, so even if they are testing ok are likely to be brittle and really need to be replaced anyway.

Also both properties I have seen this unsurprisingly have unearthed lighting circuits which is another issue in itself.

I guess I have a few questions on this:

Does this type of installation have a name?

On a condition report what code would you give it? (I assume C3 if ZS at accessory is ok? with a recommendation to rewire or at least monitor installation condition regularly)

Also is this set up mentioned specifically in any regs? if so, any pointers on where to look would be appriciated.

I did have a look at other threads and found the odd post eluding to this issue but nothing comprehensive, so any input you have on this would be good!

Thanks!

 

[davesparks]

Yes using a single cpc for multiple circuits is mentioned in a specific regulation. This regulation permits it provided that the cpc meets the requirements for the most onerous of possible fault conditions.
I have often used a single cpc for multiple circuits in stage lighting installations where you can easily have 48 radial circuits starting and finishing in the same place

 

[th_walking_dude]

[FONT=Arial, Helvetica, sans-serif]543.1.2? I see your point. I suppose there is a world of difference between that situation and a dilapidated, residential property. If you were to have a break in the CPC it could result in a large part of the installation not being earthed.


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[amlu]

advice - rewire it if possible...
originally it was singles in metal conduit, but during the 60 years in operation may been altered plenty of times, where there was no continuity on conduits bare wire was added, sometimes singles without conduit + bare wire.

 

[davesparks]

[FONT=Arial, Helvetica, sans-serif]543.1.2? I see your point. I suppose there is a world of difference between that situation and a dilapidated, residential property. If you were to have a break in the CPC it could result in a large part of the installation not being earthed.


[/FONT]

Yes it could, but you are carrying out the testing to confirm that it has not broken aren't you?
I am not saying there may not be other observations to be made and coded or that this may not be a factor to be considered when recommending the best way to improve the installation. But taken in isolation the use of a single cpc for multiple circuits is not something to be coded.

 

[davesparks]

advice - rewire it if possible...
originally it was singles in metal conduit, but during the 60 years in operation may been altered plenty of times, where there was no continuity on conduits bare wire was added, sometimes singles without conduit + bare wire.

Have you visited this property? If not how do you know that the installation was in metal conduit?

 

[th_walking_dude]

Yes it could, but you are carrying out the testing to confirm that it has not broken aren't you?

Yes of course, My concern would be for the future but I do see where you are coming from if it's covered in the regs then it's covered in the regs, doesn't matter how I feel about it!

 

[ImpededLoop]

The last one that I rewired was wired in twin with separate, bare cpc's from each socket outlet which were all individually buried directly in the garden. It was wired in the late 50's.

 

[th_walking_dude]

The last one that I rewired was wired in twin with separate, bare cpc's from each socket outlet which were all individually buried directly in the garden. It was wired in the late 50's.

Brutal, it always amazes me there are installs that are that old still about. I think the old people don't want to rip down the 60s wallpaper!