Security Light earth

[wrighty263]

Hi all,

I have a outside security light that is fed by a twin and earth on the downstairs lighting circuit.

There is an additional 4mm earth that runs from a nearby socket, through the wall and is clipped on an external wall with a disused co-axial/telephone cable.

After investigation, i can see why the previous owner has done this - the earth on the feed twin and earth has disintegrated, with no length to terminate. i have investigated the possibility of re-running the cable, however dont believe this is viable (Cable routed under varnished finish floor boards, and no chance of fishing through).

My question is, can you take an earth from a different circuit and if so is the earth ok to be directly clipped to an external wall (No mechanical protection)

Many thanks for your help

 

[Chri5]

Buy a plastic security light, most don't need an earth.

 

[dhutch]

See 'Double insulated appliances'

http://www.diyfixit.co.uk/electrics/wiring-a-plug.html


Daniel

 

[Scoby_Beasley]

After investigation, i can see why the previous owner has done this - the earth on the feed twin and earth has disintegrated, with no length to terminate.

More than likely been cut back as the old/present fitting was/is double insulated. ^^^^^

 

[wrighty263]

The switch that isolates said security light has a metal faceplate and back box. Do I have to replace the metal faceplate with plastic?

 

[Chri5]

The switch that isolates said security light has a metal faceplate and back box. Do I have to replace the metal faceplate with plastic?

That will require an earth, so if there isn't one you will need to have a plastic face plate.

You could test running a flying lead from main earth point through a multi meter set on continuity. If the earth is connected you will have a beep and continuity.

 

[ban-all-sheds]

If there is no earth wire in the cable which you can attach to the faceplate OR if there is one but you cannot be sure that there's continuity back to the earth bar in the CU (remembering that your wiring has been fiddled with by a t**t who likes to cut earth wires away) then you have to replace it.

 

[wrighty263]

Thanks for responses. There is no way there is continuity back to cu.

When inspecting the cable bits of earth were crumbling away in my hands.

Will replace faceplate and backbox and outside light with a double insulated one. Then I can tidy away the borrowed earth as it looks dodge. Many thanks

 

[bernardgreen]

There is no way there is continuity back to cu.
When inspecting the cable bits of earth were crumbling away in my hands.

That is bad news,,

If the earth wire is so badly corroded to "crumble" away then it is likely the live and neutral wires will also ne corroded.

If that is the case then you have a potential hazardous situation. If ( or when ) the insulation fails there could be over a kilowatt of heating in the damaged cable ( 6 amps at 230 volts is 1380 watts ). With no earth wire there is probably no way the RCD ( if you have one ) could trip and the heat will continue for a long time.

IN short disconnect the cable at the source and replace it with new cable.

 

[ban-all-sheds]

When inspecting the cable bits of earth were crumbling away in my hands.

The copper was crumbling?

 

[Scoby_Beasley]

The copper was crumbling?

I thought that.