Safety question re switch..

[Dooby]

Mate asked me to change a switch front for them, just like for like.
Now I did it but there are so many factors I'm confused as to how safe it is.
It was a flat in an old house conversion, wired black and red, no earth. There was a modern fuse board, RCD and MCB. The switch itself was a sort of metal plastic thing. I wasn't even sure if it was metal-effect plastic. Only thing I can't remember is was there a lug for earth on it.
My main concern too was that the switch back box was wood.

Now my understanding is you don't put metal accessories on an old un earthed system if there is corresponding rewirable fuses. But can if is MCB/RCD protected.

The only thing I did was change the front of the light switch but I'm really fretting now if it's unsafe.

 

[telectrix]

you don't fit metal switches if there's no cpc, RCD or not. go back and fit a plastic one.

 

[Dooby]

Thank you I'll do that. I'd checked with experienced sparks beforehand who'd said ok with RCD etc but I've not been happy about it..

 

[telectrix]

those "experienced sparks" are idiots. there's several threads on this forum about changing CUs when there's no cpc on lighting circuits. while there, i'd check to see if he has any more classII lights and/or switches and advise him to replace any with plastic ones. might make you look a pratt in his eyes for being wrong in the first place, but that's better than killing him and/or his kids. also, there should be a label on the CU stating that " lighting circuit/s have no cpc/s and class I fittings must not be used. the alternative is to rewire the circuits or run in separate 4mm cpc.

 

[Dooby]

Thanks again for that. I wasn't sure as other sparks seemed so confident about it and I'm totally neurotic and worry about every job I do that I'll kill people so wasn't sure if I was being over cautious! My mate isnt in the flat this week so glad I had time to come on here and check

 

[SirKit Breaker]

Thanks again for that. I wasn't sure as other sparks seemed so confident about it and I'm totally neurotic and worry about every job I do that I'll kill people so wasn't sure if I was being over cautious! My mate isnt in the flat this week so glad I had time to come on here and check

Dooby,

A bit of info for you.

RCD's work on earth leakage. It has to have the same amount of current passing through the Line and Neutral to work properly. If current leaks to earth, and it gets higher than the rating of the RCD (in your case it should be 30mA) then the RCD will trip off and disconnect the circuit/s it is protecting.

You have changed a light switch, and fitted a metal one, at your switch there is no connection to earth (no cpc), therefore when your switch basic protection (its construction) fails, the current will leak to the metal face plate, and because you have no fault protection (cpc), it will stay there until someone earths it with their fingers. If you have a cpc, then the fault current will go to earth, and the RCD will trip, because the line and neutral current of the lighting circuit will go out of balance very quickly

The RCD will never know.

Cheers............Howard