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Black, Grey Brown

Posted: Thu Nov 08, 2018 11:49 am
by tonk
Opened a junction box in my bathroom to find and earth cable, black, grey and brown cable. Confused me as expected to find earth, brown, blue.
Electricians have left it there (new Build). With the bathroom lights on, from memory brown and black are live.
The is a fan in the same room
Any early thoughts, as I would like to install a bathroom light.
Thanks Tonk

Re: Black, Grey Brown

Posted: Thu Nov 08, 2018 3:20 pm
by wine~o
brown/black/grey is the "harmonised" 3 core, one will be permanent live, one switched live and one neutral. Without a multimeter impossible to tell which is which.

Re: Black, Grey Brown

Posted: Thu Nov 08, 2018 10:04 pm
by tonk
Thanks Wino..
Got me thinking, will get back to you if this is ok.

Re: Black, Grey Brown

Posted: Sat Nov 17, 2018 9:28 am
by ericmark
Three core and earth is used to supply bathroom fans and two way switches, pre-harmonisation it was red, yellow, blue UK, brown, black, black Europe, grey was used when we harmonised it replaced the blue, so some electricians used the grey as neutral others used black as neutral either way the wire should be over sleeved so you should have one wire brown over sleeved and other blue over sleeved for a fan, and two brown over sleeved for a two way switch.

However there is no law forcing over sleeving and to be frank easier to trace with three colours so over sleeving is being a little pedantic. Again we should produce plans showing every junction box, socket and light fitting, but never seen it done with domestic.

I wonder why there is a junction box in the bathroom? I will guess down lighters? problem with a bathroom is unless over a set height (2.25 meters) there are special regulations as to what can be fitted, I know my bathroom has a pendent light, but that was fitted 1980 and at that time there was no shower fitted.

Pictures are always good.