Strange Voltages

[ericmark]

The point is the electrical safety council although they say you should try and persuade the owner to re-wire still give instructions on how to live with lights without any earths.

However much I personally think it is wrong we still have a major player in the house wiring electrical scene advocating that one can continue to use pre-1964 wiring today.

So with non metal light fittings and plastic switches with insulated bungs covering the fixing screws or similar one can continue to use non earthed lights. One can only maintain the lights one can't add to them or use metal fittings.

With pre 1960's light switches they were often fitted on squares of wood and made of Bakelite. There was no back box as such and the fixing screws went in to the plastic so there was no way the cover fixing screws could become live. But where a metal back box is used then there is a possibility a wire can touch back box and so the fixing screws could become live. Some switches come with plastic plugs which cover the fixing screws and the LAP grid switches are plastic and have a cover which clips on covering the fixing screws.

So what it means until rewired one has very little to choose from, you have to use fittings and switches which have very little metal in them.

Twin and earth was around in the 1950's but electricians just did not connect the earth. I have tried to connect the earths but so often you find some where there is a hidden junction box and after hours of work you still can't get the earths connected.

In wiring post 1964 then we are looking at a completely different situation it clearly should be earthed. There is nothing in "Guardamar"'s post to say what age the wiring is.

So from the readings given clearly what ever he thought was earthed clearly is not bonded to earth although finding a true earth may mean he gets correct readings it does not really help in getting an earth to the lamp.

When Guardamar gives us an approximate date for last re-wire then we can start giving real advice but until that point we don't really know if this is normal (for age of wiring) or not so can't really comment on what should be done.

 

[JohnW2]

However much I personally think it is wrong we still have a major player in the house wiring electrical scene advocating that one can continue to use pre-1964 wiring today. ... So with non metal light fittings and plastic switches with insulated bungs covering the fixing screws or similar one can continue to use non earthed lights. One can only maintain the lights one can't add to them or use metal fittings.....

I think there is a lot of wild speculation going on here. The OP referred to measured L-E and N-E voltages at a JB on the lighting circuit. Although it is not inevitably the case, this seems to make it very probable that there is a earth/CPC at the JB, and hence in the lighting circuit in general - so I don't really understand all this talk about pre-1964 installations without an earth/CPC in the lighting circuit.

Kind Regards, John