Running new lighting circuit earth

[Hellmooth]

Hi quick question, got a newly wired lighting circuit that has had the earths chopped, would be easier for me to run a new earth alongside, is there a minimum size of earth if ran in singles and not protected by an outer sheath, got 4mm in my head but not sure where from!

 

[telectrix]

correct. 4mm if not mechanically protected.

 

[Richard Burns]

543.1 minimum sizes of cpc as Tel says

 

[Hellmooth]

Thanks guys.

 

[Deleted member 26818]

2.5mm if insulated and sheathed.

 

[Hellmooth]

2.5mm if insulated and sheathed.

Whats the reasoning for that? Surely if you ran an insulated and sheathed cable in it would have better protection than the 1mm earth of the t+e?

 

[Hellmooth]

Not that it's exactly protected for that matter!

 

[Richard Burns]

A 1mm² single core cable is considered too weak to be installed without the additional support of other cores to strengthen them considering the stresses to which the cable might be subjected in installation.

 

[Deleted member 26818]

Whats the reasoning for that? Surely if you ran an insulated and sheathed cable in it would have better protection than the 1mm earth of the t+e?

Minimum CSA for an earth conductor (that is not part of a multi-core cable or contained in an enclosure forming part of a wiring system) is 4mm without mechanical protection and 2.5mm with.
The sheath is considered mechanical protection.

 

[Hellmooth]

Minimum CSA for an earth conductor (that is not part of a multi-core cable or contained in an enclosure forming part of a wiring system) is 4mm without mechanical protection and 2.5mm with.
The sheath is considered mechanical protection.

So for example, what if I just ran a new 1.5mm t+e alongside the existing circuit, but only used the earth, it would only be a 1mm so wouldn't comply, even though in the original circuit it obviously does, thoughts?

 

[Dave OCD]

So for example, what if I just ran a new 1.5mm t+e alongside the existing circuit, but only used the earth, it would only be a 1mm so wouldn't comply, even though in the original circuit it obviously does, thoughts?

Good point mate but then you could sleeve all 3 cores g/y and have a 4mm earth. :laugh3:

 

[Hellmooth]

Good point mate but then you could sleeve all 3 cores g/y and have a 4mm earth. :laugh3:

Lol where would we be without you Dave :clap:

 

[Dave OCD]

I like to have a positive approach to these issues mate.:leaving:

 

[Deleted member 26818]

No, it would comply, as the 1mm CPC would be part of a multi-core cable.

 

[Hellmooth]

No, it would comply, as the 1mm CPC would be part of a multi-core cable.

Yeah I suppose, I kind of mixed myself up a bit, so it would mean a 2.5mm single with a sheath? Can you get double insulated single core earth cable? I know you get brown and neutral!

 

[Hellmooth]

Just googled it, you don't, but could always sleeve a brown or blue, not that I would I have a drum of 4mm earth anyway lol this has purely been educational!

 

[K Macnamara]

Forgive me if I have read your post wrong. Is the installed circuit wired in t&e? What is the reference method? If it is then I wouldn't suggest running a separate earth as this is not considered as good practice by the NICEIC. If you were to install an earth as you suggest by installing new t&e you might as well rewire the circuit wouldn't you? If the circuit is in singles and you can run an earth bingo. The alternative however could be to make the circuit a Class II and mark it up at the DB as a circuit without an earth.

 

[Leesparkykent]

Forgive me if I have read your post wrong. Is the installed circuit wired in t&e? What is the reference method? If it is then I wouldn't suggest running a separate earth as this is not considered as good practice by the NICEIC. If you were to install an earth as you suggest by installing new t&e you might as well rewire the circuit wouldn't you? If the circuit is in singles and you can run an earth bingo. The alternative however could be to make the circuit a Class II and mark it up at the DB as a circuit without an earth.

get your tin hat on lol.

 

[Hellmooth]

Forgive me if I have read your post wrong. Is the installed circuit wired in t&e? What is the reference method? If it is then I wouldn't suggest running a separate earth as this is not considered as good practice by the NICEIC. If you were to install an earth as you suggest by installing new t&e you might as well rewire the circuit wouldn't you? If the circuit is in singles and you can run an earth bingo. The alternative however could be to make the circuit a Class II and mark it up at the DB as a circuit without an earth.

Yes it is wired in t&e, RM 100, I don't think it's great practice either tbh but it's only for some downlights that have been installed by notching out the bottom of joists and plastering over, to rewire would be a hassle, it's mainly for testing purposes, I'm sure the fittings are class II, need to double check, it's part of a rewire but this is fairly new wiring, if I could do without running in new cables it would save a lot of time and hassle! Good point about marking up at DB but would rather it had an earth at the fittings!

 

[davesparks]

If it's new wiring then the options are to fix it properly or fix it properly, preferably at the expensive of the idiot who wired it that way in the first place.

The idea of making a whole circuit 'class 2' needs a bit more thought than just sticking a sticker on the DB. For a start I believe, but would have to check, that using double insulation as a protective measure is only permitted in installations under the supervision of skilled persons, so not suitable for domestic.

The idea of adding RCDs and a sticker at the DB is a myth which has grown up in recent years to dodge around requiring circuits wired in imperial twin cable, but it does not feature in bs7671.