1940s Lighting Circuit in Steel Trunking


Postby Spankplanker » Mon Sep 07, 2009 9:43 pm

I'm in the process of fitting flushmount sockets and light switches in a 1940s ex-council lower villa.

The lighting circuit is armoured by steel trunking buried beneath the plaster and I've been having a real struggle trying trying to remove the old style, round switch mounts so I can replace then with modern boxes. The best technique I've come up with so far involves a hacksaw and vice-grips, but with my last effort, I managed to nick one of the cables and need to replace it.

I've traced the cable trunking up to a 5-way steel junction box in the ceiling void, above the ceiling rose and this is where I am at a loss!

Does anybody have a clue as to how to remove these junction boxes from below?

The easiest way would be to lift the floorboards from above and just thread through the new cable, but I don't have access to the upstairs villa.

Anybody had any experience with these?
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Postby kbrownie » Tue Sep 08, 2009 9:04 am

They metal conduit, used as containment for the cables. They may also be used as the earth for the circuits. Earth continuity must be maintained at all time.
The conduit pipes uasuall are fixed in by a nut at boxes you may be able to remove them that way.
You mention Villa, so I'd be interest if this was a UK project as certain standards need to be complied to:
www.diydoctor.org.uk/projects/partp.htm
Google "competentperson.co.uk"
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Postby bd3cc » Tue Sep 08, 2009 9:31 pm

Have rewired London flats with the same sytem. usually new cables can be tied to existing and pulld through at least one bend.
I would cut out the old switch boxes and replace with modern square, but as kb says you must mantain the integrity of the earthing system, and may need to pull a new earthwire through and ensure connection to the existing steel conduit.
It seems to me that all this work would come under Part P regulations, and would therefore need to be certified by a registered sparky.
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