Wiring an Outside Light - no earth query

longtimelurker54

Hi,

We have just replaced an external/garden light. When doing so we noticed that the existing mains cable to the old light did not have any earth (just live and neutral wires) and are wondering if this is a problem (the light is plastic, not metal and does not have a label saying it must be earthed).

We have re-wired other lights inside the house and there was earth to those and it was easy to do a like for like switch. We just don't understand why there was no earth wire present in the mains to the outside light.

We have one more outside light to replace and haven't unwired that yet because we have a fancier light to put in its place which is metal and does have a sticker on it saying it "must be earthed". Would it be unsafe to use this light fitting if when we unwire the old one we find that that too has no earth cable in the mains supplying it?

Is there anything we can do to get around this as we have had this light ages now and can't return it to shop so would like to use it if we can.

Many thx.

macman

What circuit are these garden lights connected to?
Is the 'fancy' new light even suitable for external use?

shandypants5

Hello,
If the new fitting says it must be earthed, then it MUST be earthed or it may become live if there is a fault.

What sort of cable is used to feed the existing lights and is it buried underground or run along a fence or something similar.

Sometimes people use a type of cable that has a heavy metal armoured shield wrapped around it to protect it from spades etc.
This shield is sometimes used instead of an earth wire and "bonded" at each end.

ormus

if the fitting is all plastic then usually there is not even a facilty (tag or screw) for an earth connection.
plastic units are normally double insulated.

longtimelurker54

Hi,

Many thx for the replies and to answer some of the questions posed:

Assume it is on the ordinary lighting circuit but will check this by taking out that circuit and seeing if these lights remain off.

Can't do this today as it's pouring down here but basically the light is on the brick wall forming the rear of the house. The cable comes straight through the wall from inside and it looks to be an ordinary type of cable (not armoured).

There are two external lights. We replaced the other one and discovered that the cable to that had no earth, but it didn't matter at the time as the replacement fitting we used was all plastic and didn't need to be earthed.

The other fitting we're trying to put up is metal and says it must be earthed, hence our question posted here.

I suppose the earth could have been trimmed back if the existing fitting did not require earth - will need to check this when the weather clears up. Otherwise it just seems strange because the rest of the house wiring all has earth.

If it is the case that the earth has been trimmed back I guess we may have to join cable to lengthen it to be able to reach the new fitting - what's the best way to do this safely, given the cable is on an external wall?

Many thx.

macman

The lighting circuit itself may not be earthed-many older properties are not.

googler

If the cable goes straight through the wall from switch to light, then surely you can pull a length of 3-core through using the 2-core as a feeder?

You seem to suggest the feed wire from switch to light is 2-core - on inspection of the switch, is the supply to this a 3-core cable?

longtimelurker54

Hi there,

Sorry, I didn't explain that very well. The switch is inside on the kitchen wall but this light is on an opposite external wall - so it's not possible to see where/how the cable runs from it to the light outside - it goes to the other side of the kitchen somehow but I can't see its route as it's hidden behind plaster etc., etc.

I hope to take a closer look outside at the wiring when it dries up.

It is an Edwardian house but I think the lighting must have been rewired at some point because when we were replacing internal lights from recollection they were all earthed.

tartanterra

ormus wrote: »

if the fitting is all plastic then usually there is not even a facilty (tag or screw) for an earth connection.
plastic units are normally double insulated.

Even if the light fitting is double insulated and has no requirement for an earth, the supply cable must have an earth running through it's length in case it becomes compromised/damaged in some way.

As it is in an outside location, it should also be RCD protected.

If the cable is old it is also advisable to have the cable tested as they degrade over time.