CPC/Earth feed to Light Switch Back Box

[BettyBoop44]

Hi
Just a bit of info required , just been checking all over the house checking for a earth feed to light fittings and switches , ( a friend informed yesterday that there friend have more or less sold there house , but an electrcal inspection has come up with no cpc to all the light switches ) .
I have found 3 light switch back boxes that do not have a earth feed to them , now the question is can I fit a plastic box inplace of the metal one that is in there and not need a earth feed to them ! .
All the light fittings have a earth feed to them ! , every circuit in the house is protected by a RCD .
cheers
BB

 

[Pat H]

I assume these are flush to the wall boxes and plastic isn't ideal for this. Do the existing boxes have plastic lugs for the cover screws.

Good point. One of the common issues with light switches is the screws from the face plate being long and puncturing the wires behind. Potentially leaving a live screw head.
A plastic push in cover for each screw helps reduce that risk. Also taking care of the position of the cables as the face plate closes up and the length of the securing screws helps.

 

[Pete999]

If the back box and light switch are both non metallic then no CPC is required.
However care must be taken that a later owner doesn't add metal faced switches and a risk is created. We don't rely on RCD for protection as they can fail.
You could leave a note in the plastic backbox as a reminder that no CPC is present and no metal switches to be installed as a sort of gift to the next owner.

Earthing may not be needed, but cpcs need to be present regardless

 

[Pete999]

Hi
Thanks for your reply , I am talking about my house not my friends friends house ! , the feed to the lights were also just 2 core flat , I fit a cpc to them a long time ago direct from the cpc bonding terminal next to the meter ,but did not think about the light switches , the kitchen and lounge light switches have a cpc they where put in when some workwas done there prob about 5 year ago .

cheers

BB

BB your post has become confusing, what you need is a comprehensive EICR Electrical Installation Condition Report carried out by a competent Electrician, things have become difficult being drip fed information, get a Spark in to do the EICR and go from there.

 

[Des 56]

What size cpc and what routing did you take when installing he seperate cpc as there are regulations governing what should be done

 

[Ian1981]

1. Taken from best practice guide 1 with installation containing no cpc to lights.
   This is regarding a consumer unit change but nevertheless contains some useful information I think.
   Sorry about the quality as it's copied and pasted
   
   Carry out a continuity test applied between the earthing terminal in the exis ng consumer unit and all Class I light fittings and metal plate accessories.
   
   If the resistance value is 1 Ω or less, the equipment may be considered to be earthed.
   

1. 10.5.3. An insula on resistance test should be applied between the live conductors (line and neutral connected together) and the earthing terminal in the consumer unit, with that terminal connected to the means of earthing.
   
   The resistance should be at least 1 MΩ.
   
   
2. 10.5.4. An insula on resistance test should be applied between line and neutral connected together
   and the exposed-conduc ve-parts of every Class I lighting and metal switch plate found to not be earthed by the con nuity tes ng described in Sec on 10.5.2.
   
   The resistance should be at least 1 MΩ.
   

10.5.5 If the circuit does not ful l the requirements
of either 10.5.3 or 10.5.4. there would be a
risk of electric shock if the circuit were to be re-energised. The customer must be advised in wri ng that this danger exists, and that the circuit must be disconnected from the supply and should not be connected into a new consumer unit.

10.6. If the customer will not agree to the risk assessment as described in Sec on 10.5. being carried out,
they should be advised that a ligh ng circuit having no protec ve conductor that has metal or Class I switches, light ngs or other accessories ed

is poten ally dangerous (and so would warrant a Code C2 classi ca on in an Electrical Installa on Condi on Report).

This will mean that the circuit cannot be connected into a new consumer unit (see Sec on 4.3 of this Guide).

10.7. It should be noted that the protec ve measure double or reinforced insula on is only applicable
to electrical installa ons or circuits therein that are under e ec ve supervision in normal use to ensure that no change is made that would impair the e ec veness of the protec ve measure (regula on 412.1.3). Domes c and similar premises falling within the scope of this Guide cannot be considered to be under e ec ve supervision.

 

[westward10]

Not saying a word it is Sunday.

 

[BettyBoop44]

OK guys thank you for all your feedback the conclusion they have to have a cpc to each box/switch , there is only 3 walls to chase down other half will not be happy though it has to be done , would not of looked if it was not for the info my friend told me .

thanks again

BB

 

[BettyBoop44]

What size cpc and what routing did you take when installing he seperate cpc as there are regulations governing what should be done

Hi
I took a 2.5mm direct from the earth bonding box next to meter ! , I have to also mention that this problem is only on the lower floor switches upstairs are all fine .
ps: what reg is it that covers that ! .
BB

I assume these are flush to the wall boxes and plastic isn't ideal for this. Do the existing boxes have plastic lugs for the cover screws.

Yes.

 

[Pete999]

OK guys thank you for all your feedback the conclusion they have to have a cpc to each box/switch , there is only 3 walls to chase down other half will not be happy though it has to be done , would not of looked if it was not for the info my friend told me .

thanks again

BB

And each light point

 

[Des 56]

Hi
I took a 2.5mm direct from the earth bonding box next to meter ! , I have to also mention that this problem is only on the lower floor switches upstairs are all fine .
ps: what reg is it that covers that ! .
BB


543.1.1

 

[BettyBoop44]

And each light point

Read my #10 post in this thread ! .

 

[davesparks]

Hi
I really need a answer to my first post ie , can I fit a plastic back box in place of the metal one and then not need a cpc !

No, the regulations require that the cpc be present at every point in the circuit regardless of materials used.

 

[davesparks]

If the back box and light switch are both non metallic then no CPC is required.
.

This is incorrect, the regulations require that the cpc is present at every point on circuits where ADS is used.

 

[Pete999]

Hi
Thanks for your reply , I am talking about my house not my friends friends house ! , the feed to the lights were also just 2 core flat , I fit a cpc to them a long time ago direct from the cpc bonding terminal next to the meter ,but did not think about the light switches , the kitchen and lounge light switches have a cpc they where put in when some workwas done there prob about 5 year ago .

cheers

BB

What size cpc did you use and why take from a BONDING conductor connection, ?

 

[telectrix]

What size cpc did you use and why take from a BONDING conductor connection, ?

it's also an earthing terminal (MET). better would be to connect to the earth bar in the CU in the correct point for the circuit. and, if not mechanically protected, should be min. 4mm, but that's a minor point.