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Howdi this is probaly a really stupid question but can you use 2 2c+e cables instead of 1 3c+e? 
yes
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Do what 
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Thanks for answering my stooopid question securespark and 1john tata
Do you mean for a two way switching arrangement, or for a 3 phase circuit?
yes but make sure you connect both earths.
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Mr Lighting it's for adding a third switch to a 2 way by changing 2nd switch to a 2g intermediate then adding a third switch using 2 x 1.5mm 2c+e
kevindgas yep indeed matey always
kevindgas yep indeed matey always
Oh ok, thats fine then 
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Mr Lighting aren't 3 phase circuits only used in electric generator plants?
Three phase is standard in all industrial installations, and all but the very smallest of commercial installations.
It is sometimes used in big houses too, but it would be unusual to find in a 'normal' house.
It is sometimes used in big houses too, but it would be unusual to find in a 'normal' house.
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Oh right I didn't know that businesses used it I thought only massive beast generator plants used it
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Single phase is used more now since the introduction of HF (High Frequency) florescent units. But because of the stroboscopic effect of discharge lamps three phase was the norm for anywhere with rotating machinery.
As to splitting feed and return that can produce EMC problems with mains hum found on all sorts. So although you can use separate cables they need to run in the same path and if there is any ferrous metal work must go through same holes or transformer effect can heat things up.
There is also a problem with earths. Unless to earth runs in same cable as lives they have to be 4mm so as already said both cables need earths connecting.
Years ago it was common to use two core cable for two way switching and used twin switches and "Borrow" the line feed. However this caused interference with modern equipment and it was all too easy for those "borrowed" lines to become "borrowed" neutrals and so the practice was stopped.
I would assume what you are contemplating would be OK but I would be wary of just saying it was OK in case you were going to do something which would fall foul of the odd cases. So the two cables should take the same route and use all the same holes and you should be OK.
As to splitting feed and return that can produce EMC problems with mains hum found on all sorts. So although you can use separate cables they need to run in the same path and if there is any ferrous metal work must go through same holes or transformer effect can heat things up.
There is also a problem with earths. Unless to earth runs in same cable as lives they have to be 4mm so as already said both cables need earths connecting.
Years ago it was common to use two core cable for two way switching and used twin switches and "Borrow" the line feed. However this caused interference with modern equipment and it was all too easy for those "borrowed" lines to become "borrowed" neutrals and so the practice was stopped.
I would assume what you are contemplating would be OK but I would be wary of just saying it was OK in case you were going to do something which would fall foul of the odd cases. So the two cables should take the same route and use all the same holes and you should be OK.
Mr Lighting it's for adding a third switch to a 2 way by changing 2nd switch to a 2g intermediate then adding a third switch using 2 x 1.5mm 2c+e
kevindgas yep indeed matey always
You could leave the two way switch where it is and run the two 2cores to the new position.....and fit the intermediate there
It would use all 4 cores. Have a think about it
If you only three of the four possible cores, do not commit the sin and cut the spare core - terminate it in a terminal block leaving the core the same length as the others (and not as short as all DIY'ers seem to do!).
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Okay thanks eric very informative, will do as you said keep 'em together okay thanks
Thanx Lectrician I was unaware I could do that would be much easier to keep same second switch and would have cut 4th core but won't now on your advice thanx
Thanx Lectrician I was unaware I could do that would be much easier to keep same second switch and would have cut 4th core but won't now on your advice thanx
Connect your spare core to earth (after sleeving it with some g/y)
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