Separate 4mm CPC to Lighting - Not run with original cable

[Lightdream]

Hello all,

A friend of mine as asked me to take a look at his installation and pick out any obvious work he needs doing, before he gets a PIR done.

It's a three bedroom house and all circuits are protected with a dual RCD set up. Mix of old and new colours at CU and all labelled correctly and lighting appears to be sleeved correctly at switches and ceiling roses. Meter tails 25mm, Main earth 16mm, and bonding to extraneous (water and gas pipes) is 10mm and continuous. He simply wants a visual inspection, so I won't be completing any tests - the PIR will see to that.

The one thing i'm not sure about is the CPC run on the lighting. Both upstairs and downstairs were wired in 1mm twin (without CPC) and it seems at some point, a 4mm CPC has been run separately to the ceiling roses and switches. However, there are points where the 4mm has not been run with the original cable. For instance, the upstairs bedroom backs onto an airing cupboard/storeroom. The route for the 4mm CPC drops from the attic, into the storeroom, through the wall and into the bedroom switch through the rear of the backbox. The original twin cable drops vertically from the loft, on the bedroom side of the wall, through the top of the backbox and has been plastered over.

Although the CPC provides protection at both the switch and the ceiling rose, it is obviously not providing any protection along the route of the lighting cable. Any idea what the PIR might have to say about this? Perhaps a Code 3 or 4? Any replies appreciated.

 

[wallyanker]

Not 100% on this but I'm sure there was another thread on here not so long back stating that a 4mm CPC is the correct size if it was routed at a later date and does not follow the same route as the original cable.

 

[Strima]

Although it's always best practice to follow the original route it's not always possible. As long as there's continuity of the CPC to all points then I can't see too many problems.

 

[Snapester]

I would test points with a wander lead to confirm CPC continuity throughout the circuit, if you cannot verify the continuity with a test then i would code this a 3 and pop a sticker on the consumer unit stating only plastic accessories to be used on lighting circuit as no earth provided.

 

[Guest55]

its route is irrelevent , so long as it picks up all points and has good continuity then its fine , trying to route it along side the original wiring is a lot more work and pointless.

 

[kingeri]

I'd defo take the shortest, easiest route. As said, could be a lot harder to follow the original route - and for little benefit!

 

[Doomed]

I thought the smallest size for an unprotected earthing wire was 6mm? yes? no?

 

[Snapester]

No, 4mm is the smallest that requires no
mechanical protection.

 

[telectrix]

no, it's 4mm if no mechanical protection . (you may be thinking of main earthing/bondind with 6mm)

 

[Paul.M]

Let's not confuse earthing a point so you can fit a class I light or switch with a cpc which is there to protect the cable. If at the time of the original install a cpc was not required under the regs then no code should be issued but as others above have already said, test continuity at each point so class I fittings can be used.

 

[DurhamSparky]

the old what size cable chesnut!! !!

just pull a lenght of the cheese wire "1.5" from T&E run that along side it with no sheath and connect your fittings! that way it looks original and you have an earth...!

might even be better if you throw a few JB's in and twist it around the top to form some kind of locking mechanism as to not be able to open the JB...


Just a thought...!



back to original question YES its fine..!

 

[Lightdream]

Thought as much but thanks to all of you for your replies.