No Earth wire on lighting circuit

[premierfc]

a friend of mine has moved this week into a new house(1930 semi) he was changing the light fitting in the living room and found there was no earth to the ceiling rose.the light fitting he wants to fit is metal.i said i would ask the question.any help much appreciated.ps he said all sockets lights etc look modern and all backboxes have earths to them?

 

[davy_owen_88]

It is common in old houses for them to lack a CPC on the lighting circuit. Unless he gets the circuits rewired he should not fit any metal fittings. Stick to plastic or double insulated fittings.

How does he mean there is an earth at the switch? If there is then it would be at the ceiling rose too because the switch wire goes to the ceiling rose so ask him to confirm.

I hope this is what you were looking for because you failed to ask any questions.

 

[pcboffinuk]

As Davy says it is common for old houses not to have an earth on the lighting circuit. It is probably a sign that a rewire of at least that circuit may be due.

However, if there really is an earth at the backboxes (and not just a short length between backbox and switch) then it may be worth checking the ceiling rose again.

I've seen cases where someone fitting a plastic fitting hasn't known what to do with the earth and cut it back - very bad practise but may be the case here.

Gavin

 

[bernardgreen]

It wasn't un-usual to find earths taken to switches as these were touched in use bit not taken to roses as no one would touch these in normal use.

 

[premierfc]

thanks for all your replies.i will speak to him again and let you know

 

[Norv]

If the CU would accept it, would it be possible to fit an RCBO to give the circuit some earth protection ?

 

[pcboffinuk]

If the CU would accept it, would it be possible to fit an RCBO to give the circuit some earth protection ?

Sorry Norv, but while a RCBO might be a good idea (step forward JohnD ) They don't give a circuit 'some earth protection'.

They are useful in places where the earth fault path is not good enough to trip a breaker/fuse quickly enough to satisfy the regs. But they are not a replacement for an earth if metal fittings are present.

Consider that there was a fault within a metal fitting with no earth - the only fault path would be the poor sod holding onto it while changing a bulb - and 30ma could easily cause very serious injury or even death in the elderly, infirm etc.

Gavin

 

[pcboffinuk]

the only fault path would be the poor s** holding onto it

I can't believe the rude word filter doesn't allow s-o-d - what happens in the gardening forum?

 

[IJWS15]

If he doesn't have an earth on the lighting circuit he may also have rubber insulated cables (bad) and Neutral fuses (dangerous).

I would guess the house does not have many sockets!

Suggest you post some pictures of the wiring.

 

[RobFurn]

this isnt a bad link on the subject:

http://www.niceic.org.uk/downloads/BestPracGuideJan07secure.pdf

 

[securespark]

Not sure that 30mA would cause injury or death - that level was chosen as the upper limit above which injury or death may occur.

 

[pcboffinuk]

Not sure that 30mA would cause injury or death

For a fit and able adult maybe, but for a child? or a pensioner? I'm guessing that controlled trials have never been carried out

I wasn't saying that an rcd might not be a good idea to improve safety (although there is the argument about the lights tripping while up a ladder changing a bulb hazard), just that its not imo a solution for a lighting circuit with no earth but metal (non class 2) fittings.

With an rcd fitted even a poor earth gives a fault somewhere to go and (eventually) trip the rcd as opposed to waiting for someone to grab hold of the fitting and relying on the rcd to trip before the person takes a lethal dose....

Unless I'm missing something, in which case please put me right - I'm still learning what is accepted (and acceptable) practise in the 'wild'.

Gavin

 

[plugwash]

using an rcd as a substitute for adequate earthing on old installations is considered acceptable in much of the world but we brits have higher standards than that.