Adding to existing lighting with no CPC

[TomSparkman]

Hi everyone,

I am currently installing an additional 4 way CU which is to serve a new extension on the customers house. They have also asked me to alter one of their existing 2 way stairs lighting so that they can have an intermediate switch incorporated (a switch at either end of the upstairs landing aswell as the one at the bottom of the stairs).
Pretty straightforward... pull a 3 for from tbe existing switch to the extra one and the swap the existing to an intermediate.
The problem is that there is no cpc present at the existing switch. It is wired early 1970's style using a single brown with sheath (no earth) as the switch live back to the rose.

In order to do the work they have asked for do i need to completely rewire/wire in a cpc for that lighting circuit?
Or would it be acceptable to take a single earth from one of the new circuits i have installed, to the new switch i am adding to tbe existing circuit?

Its probably a simple answer but would appreciate constructive responses, thanks

 

[Pete999]

Hi everyone,

I am currently installing an additional 4 way CU which is to serve a new extension on the customers house. They have also asked me to alter one of their existing 2 way stairs lighting so that they can have an intermediate switch incorporated (a switch at either end of the upstairs landing aswell as the one at the bottom of the stairs).
Pretty straightforward... pull a 3 for from tbe existing switch to the extra one and the swap the existing to an intermediate.
The problem is that there is no cpc present at the existing switch. It is wired early 1970's style using a single brown with sheath (no earth) as the switch live back to the rose.

In order to do the work they have asked for do i need to completely rewire/wire in a cpc for that lighting circuit?
Or would it be acceptable to take a single earth from one of the new circuits i have installed, to the new switch i am adding to tbe existing circuit?

Its probably a simple answer but would appreciate constructive responses, thanks

Have you explained / told your customer that the circuit they want altered has no cpc? therefore no metallic fittings can be used.
In order to provide a cpc to all the points on this particular circuit, assuming it's not wired in cnduit, you will need to pull in a 4mm2 cpc from the CU in order to provide the circuit in question with a suitable cpc

 

[LankyWill]

Why a 4mm? 1.5mm should suffice for a lighting circuit. If they don't want a rewire your only other option is to pull in a cpc or use plastic accessories. I'd advise them to have a rewire due to the age of the installation and to bring them up to standard.

 

[Pete999]

Why a 4mm? 1.5mm should suffice for a lighting circuit. If they don't want a rewire your only other option is to pull in a cpc or use plastic accessories. I'd advise them to have a rewire due to the age of the installation and to bring them up to standard.

I you are pulling a cpc / earth wire without mechanical protection then 4mm is the size specified by 7671 or it was, you need to check you copy of 7671 for confirmation of my statement

 

[LankyWill]

@Pete999

I think that refers to bonding cable sizes in regards to TT systems. The conduit would provide the mechanic protection in the op's case.

 

[Pete999]

@Pete999

I think that refers to bonding cable sizes in regards to TT systems. The conduit would provide the mechanic protection in the op's case.

Does the op mention that the installation is wired in conduit? Regulation 543.1.1 page 164 in the BYB

 

[westward10]

Minimum size for an unenclosed cpc or bond is 4.0.

 

[westward10]

Is it only the switch cables which do not incorporate cpcs. Single browns in the 1970s?

 

[LankyWill]

@Pete999

I must have mistook your comment in your post about conduit as the actual scenario.

I am in the wrong, please don't send @telectrix round to teach me the errors of my ways.

Sorry almighty Jedi

Padwan

 

[Pete999]

Minimum size for an unenclosed cpc or bond is 4.0.

That's what I said, didn't I?

 

[Pete999]

@Pete999

I must have mistook your comment in your post about conduit as the actual scenario.

I am in the wrong, please don't send @telectrix round to teach me the errors of my ways.

Sorry almighty Jedi

Padwan

That's OK young Jedi I will not inform Lord Vadar, although he has probably read it all by now, may the force be with you, you should take your light saber with you and disappear to the Death Star for a few weeks

 

[telectrix]

@Pete999

I must have mistook your comment in your post about conduit as the actual scenario.

I am in the wrong, please don't send @telectrix round to teach me the errors of my ways.

Sorry almighty Jedi

Padwan

a bit far for me to bring my cane. i have to delegate your punishment to pete999.

 

[Pete999]

a bit far for me to bring my cane. i have to delegate your punishment to pete999.

None of us are perfect My Lord no punishment required

 

[TomSparkman]

Have you explained / told your customer that the circuit they want altered has no cpc? therefore no metallic fittings can be used.
In order to provide a cpc to all the points on this particular circuit, assuming it's not wired in cnduit, you will need to pull in a 4mm2 cpc from the CU in order to provide the circuit in question with a suitable cpc

No i havent told the customer yet, they were out by the time i had left.

Just to clarify:
This is a domestic property, so no conduit.

There is a cpc at the ceiling rose, just no sign at the switches. This may be due to being cut off outside of the backboxes in the wall or that there isnt a cpc in the cables at all.

The additional new switch and all of the existing accessories are non metallic.

I was thinking as long as the new strapper that i pull in is earthed then that should suffice. But from what you guys are saying it sounds like i have to bring the whole circuit up to date with a cpc?
As said above could i take a single earth (either 4mm or 1.5mm insulated and sheathed earth if its available) from one of the new lighting circuits to just earth the new strapper?

 

[westward10]

What are you going to use for the new strapper a three core and cpc.

 

[Pete999]

You need to have an earth at all the points to comply so 4mm2 as described in the regulation I quoted earlier, not much use just adding a 3 core plus cpc at the mid point of the circuit. Did you read the regulation or are you fling on a shoe string? It's plain enough to understand.

 

[TomSparkman]

Yes, 3 core and cpc.

Yes is see reg. 543.1.1 now.

In light of your answers it appears as though i would have to either rewire the circuit or upgrade it with a 4mm cpc to all light fittings and switches.

If this is the case i will tell the customer, however i doubt they will want to go ahead with that due to cost

 

[TomSparkman]

You need to have an earth at all the points to comply so 4mm2 as described in the regulation I quoted earlier, not much use just adding a 3 core plus cpc at the mid point of the circuit. Did you read the regulation or are you fling on a shoe string? It's plain enough to understand.

So to clarify my knowledge. Any alteration or addition to an existing circuit forces the need whole circuit to be brought up to current regulations?

Thanks

 

[westward10]

If you decide to pull 4.0 cpc in you may as well rewire.

 

[westward10]

So to clarify my knowledge. Any alteration or addition to an existing circuit forces the need whole circuit to be brought up to current regulations?

Thanks

It is a bit grey this one, me I wouldn't touch it but if you decide to use a cable incorporating a cpc it needs to be connected to earth but just the part you put in place the other can be considered existing and is probably safe for continued use.

 

[TomSparkman]

It is a bit grey this one, me I wouldn't touch it but if you decide to use a cable incorporating a cpc it needs to be connected to earth.

I agree, the termination of the 4mm would be a nightmare aswell.

This is what is confusing me. If i did add the new strapper in then i did propose to incorporate a cpc in my cable by means of a 4mm earth provided by one of my new circuits.

As pete999 said though, it almost does seem like p#ssing in the wind adding a cpc mid circuit when all of the existing switches dont have it!

 

[telectrix]

quote to rewire the circuit in 1.0mm T/E or 1.5mm T/E. customer says no, then walk away. you are neither a bodger or a charity.

 

[westward10]

This is true like I said it is a grey area as to what to do as it is a unique situation. Do you have a scheme provider to consult. This is only my opinion but I see no problem doing it using pvc/pvc singles with no cpc to all insulated enclosures.

 

[telectrix]

So to clarify my knowledge. Any alteration or addition to an existing circuit forces the need whole circuit to be brought up to current regulations?

Thanks

yes, and RCD protection added if reqiured. e.g.by 522.6.101.

 

[Toneyz]

Have I read the post correctly is there a earth at each of the light fittings and the switch drops but the earth has been cut off at switch.

 

[westward10]

Have I read the post correctly is there a earth at each of the light fittings and the switch drops but the earth has been cut off at switch.

No I think it is pvc/pvc singles.

 

[telectrix]

so if it's singles, it's in conduit, so why is there no cpc? where's my bottle?

 

[westward10]

so if it's singles, it's in conduit, so why is there no cpc? where's my bottle?

Not singles in conduit, pvc/pvc singles.

 

[Toneyz]

make sure earth at ceiling rose run 4.0mm earth down to one of the ends of the 3 core run. You only have to make sure the work you have undertaken is compliant not forgoing the other checks eg bonding etc.

 

[7029 dave]

Rewire the circuit or walk, don't waste your time running in single cpc's not worth the aggro.

 

[TomSparkman]

To clarify its a mixture of old twin and earth and single browns for S/L back to rose. There isnt anycpc visible at switches but the sheathing has been stripped too far back so i cant see whether the cpc has been simply cut out at all switches or non existent. In the rose there is only two cpc core (loop in and out).

I think ill take the advice of either rewiring the circuit or nothing at all to be honest. I want to do a proper job, not a bodged one

 

[1Justin]

You might consider wireless. It's not nice and is something of a cop-out but it might be useful here. Megaman RF works (I think..do check) without neutral.
There are some slightly irritating switching delays, but means you can replace existing switches with class 2 switches (no CPC), and add another ("glued" to the wall), anywhere. - I have done this in the same circumstances when there was really no rewiring option.
Take care with LED bulbs though and use ones recommended by Megaman. The switches leak a small current (in order to operate) and it's enough to begin to light up some brands when "off".

 

[Pete999]

So to clarify my knowledge. Any alteration or addition to an existing circuit forces the need whole circuit to be brought up to current regulations?

Thanks

Not necessarily, you will of course need to ensure the circuit you are altering complies with 7671. Example , adding a lighting point to an existing circuit, if that circuit complies, then go ahead and add the new lighting and issue a MNWC

 

[TomSparkman]

Just to give everyone an update if anyone is interested.
I rang the Napit technical team about this problem after taking in to account everyones advice on here.
He told me that it was fine to pull a 4mm earth single from another circuit to the new switch ill be putting in. In order to make sure my 3 core is earthed.
He said that would be adequate i dont have to bring the whole circuit up to current regulations.

Thabks fpr the advice everyone

 

[Toneyz]

I would prefer to take the earth from the lighting circuit involved.

 

[telectrix]

I would prefer to take the earth from the lighting circuit involved.

me too.

 

[hightower]

CPCs weren't allowed to be omitted from lighting circuits after 1966 (I think off top of head), so if the wiring is 70s as I've read in post #1, there should be CPCs somewhere.

 

[Toneyz]

CPCs weren't allowed to be omitted from lighting circuits after 1966 (I think off top of head), so if the wiring is 70s as I've read in post #1, there should be CPCs somewhere.

There is at the light pendants but not at switch