Old lighting circuit without earth

bam

I am adding an extractor fan to an existing lighting circuit. The existing wiring is all 2 core (Red & black) with NO earth. 1960s build. The fan is double-insulated and has no earth terminal. Is it ok to add the spur, FCU etc. without any earth connection OR is it necessary to add a new earth cable from the CU to the new spur OR is it necessary to replace all the wiring from the CU? Thanks.

davy_owen_88 · Posted: Tue Mar 06, 2007 4:41 pm Post Subject:

If the fan doesn't require an earth and assuming you are not connecting a metal FCU/switch then there is no point in replacing the cable only to leave the earth disconnected.

Having no earth in the lighting circuit though does indicate an aged installation so it would be a good idea to get the circuits integrity checked out.

Is this fan going in the bathroom or kitchen? If so it is notifiable work.

Davy

plugwash · Posted: Tue Mar 06, 2007 4:44 pm Post Subject:

personally i'd say wire the fan with 2 core flex, earths that aren't actually connected to earth are a bad thing.

and make sure you use plastic boxes or screwcaps

bam · Posted: Tue Mar 06, 2007 4:54 pm Post Subject:

Thanks.
I've chosen an in-line timer fan that is mounted in the loft above the bathroom ceiling to avoid the notification requirement. I'm using all plastic SW & FCU with 3A fuse to isolate both the fan and bathroom light and pull-switch (the latter is required by the fan) and 1.5mm twin & earth.

I concur that it could be misleading to someone in the future if the new cables' earth is not connected to anything. I've already done the wiring though so I'd rather not replace it all at this stage. I have run T&E from an existing rose to the SW-FCU. The earth connects to the rose earth terminal, that has no other connections.

Is having unconnected earth ok legally? What is good practice?

Reg_Prescott · Posted: Tue Mar 06, 2007 10:35 pm Post Subject:

plugwash wrote:

personally i'd say wire the fan with 2 core flex, earths that aren't actually connected to earth are a bad thing.

and make sure you use plastic boxes or screwcaps

Plugwash or anyone

where can I get hold of screw caps for plastic light switches, or even plastic light switches with screw caps included? I am in a simliar position having moved into a 1960s house with no earth on the down stairs lighting cct. I have replaced all the light fittings and switches with plastic, but the back boxes are metal and I appreciate the possiblity the screws could become live in the event of a fault. Sorry to hijack the thread

Regards,

Mark

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bam · Posted: Wed Mar 07, 2007 8:42 pm Post Subject:

Thanks for your comments everyone. I decided that installing a new spur, or any new circuit, needs to follow modern conventions regardless of the existing wiring. I also decided that it is unacceptable to provide a "false" earth because that could be mistaken for a true earth in the future.

Fortuitously, an electric shower spur (unused) ran via the loft and is T&E and is earthed at the fuse box. I used a terminal box to terminate this spur in the loft. I then ran a single earth wire (green/yellow sleeve) the short distance from this box to the new fan spur.

I am happy that the new fan/light spur for the bathroom is now safe. The rest of the lighting circuit is earthless as before but the task of replacing all the wiring is onerous. I suppose that one should avoid using any light fixtures that are not double-insulated and, for complete safety, put those aforementioned screw caps on the light switches. Having said that I don't believe there have been any electrocutions in the house since it was built in the 1960s!