Outside Lamp and Earth

[Kroma]

Hi,

I've just bought my Dad a motion/nighttime sensing outside coach lamp from B&Q. The problem is, he now tells me that the power supply to the location where it will be fitted doesn't have an earth connection - just live and neutral.

He already has a simple on/off light in place and he seems to remember that he simply stuffed the earth wire into the brick wall!!! Is this safe? Is this legal???

Anyway, any ideas on what to do if there really IS no earth connection from the house? Should I try the 'stuffing the earth wire into the wall' trick?!

Thanks in advance,

Daz

[Sparks]

Does the new light need an earth? (as in, does it have an earth terminal)

If the existing fitting needs an earth (Generally if the fitting is metal) then no, this is not safe nor complant with the regs.

If there isn't an earth, you need to do one of two things...

1 - Install an earth wire 2 - Get a fitting that does not requre an earth, generaly a plastic one.

Sparks... (Not an electrician)

[Kroma]

Yes, the new fitting has an earth terminal.

Oh dear.

What's the easiest way to fit an earth wire?

Daz

[meow2222]

Metal fittings outdoors must always be earthed. Indoors it just protects against insulation failures, but outdoors youve got condensation, running water, spiders, insects and dirt that generally get onto the electrics, so earthling is particularly important outside.

I thought you already had one. The easiest way is to run a wire to the nearest light or socket and connect to the earth there, but this isnt compliant, as removing one circuit could leave your light unearthed. The proper way is fish that earth wire back out.

NT

[Kroma]

Ah - I think I was a bit vague with this bit.

His *current* light has an earth wire which he has poked into the brick wall as there is no earth wire coming from within the house (he was told - in the

1960s - that this would be an adequate earth)!

Fitting an earth wire will be very tricky from the location of the lamp (*):

---------------------------- | | | | | | | | | | | -------| | | | | | *|

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Daz

[Andrew Gabriel]

If there's really no earth available, you are restricted to using a double insulated luminare (which are usually plastic).

[meow2222]

I'm not entirely sure if that makes sense. Also I would not consider relying on second hand comments from 40 years ago. You need to find out whether that earth works or not.

It would have been far easier to fit a separate (plastic) motion detector and either keep the existing light or fit a plastic one. In fact that may still be your easiest option. You can reasonably expect a refund since the metal fitting is not suitable for the purpose for which you bought it.

why?

NT

[Dave Plowman (News)]

Simplest way would be to change it for one which doesn't require an earth.

Something like these:-

[Kroma]

OK, I know I need to take off the old lantern but from what my Dad has said is that he attached the current lantern's earth wire to a screw which is screwed into the brick wall. However, we may find that there is an earth wire after all as memories can be funny things!

Whatever I find... how can I check to see that any available earth works adequately?

Thanks,

Daz

[Dave Plowman (News)]

It could be there is an earth wire in the feed cable (TW&E) which is 'made off' under one of the lamp to wall fixing screws - I've seen this before.

If you can be sure no one else is in the house, wire a light between live and that earth. If it lights normally, the earth is at least connected.

(The reason to make sure no one else is around is that if the earth wire is connected to something which isn't correctly earthed doing this trick will make it live.)

[Frank Erskine]

Realistically, if the "lantern" goes faulty and a "live" connection touches the casing, you need to ensure that if you are in contact with the lantern, sufficient current flows through the "earth" wire to prevent you from being killed. Current will divide proportionately depending on the conductance of the path - either through the perhaps-damp bricks or through you! As others have said, if you can't get a "pucka" earth connection to the lantern, you really should be looking at an all-insulated (plastic cased) or double-insulated fitting. In theory you could provide an earth rod near the fitting, but the bother of ensuring that you have an adequate and permanent good earth would be outweighed by replacing the supply cable by a proper T+E supply. If the rest of the house's wiring doesn't support an earthed supply throughout the system, you _really_ should be looking at a rewire - seriously!

[Sparks]

But if you have an RCD in your consumer unit, this will (should!) trip. An RCD will have 30mA or 100mA written on it somewhere - But if it hasn't been touched since the 60's then you won't have an RCD!

Sparks... (Not an electrician)

[Dave Plowman (News)]

I sort of assumed somewhere where they're not sure about earthing isn't likely to have an RCD fitted. Unless a 'board' one due to overhead supply.

[manatbandq]

Please explain. The fitting is perfectly suitable for the purpose for which it was sold (an exterior light). If the purchaser bought something that isn't suitable for their particular situation then it's their mistake and there is no legal right to a refund. Under the sale of goods act "fit for purpose" means capable of doing what it's meant to do, not neccessarily what the purchaser wants it to do.

If it was described and sold as being suitable for installation where there is no earth available (there's no evidence of this in the OP) then obviously that's a different matter and it isn't fit for purpose.

MBQ

[meow2222]

AIUI if sales staff say its fit for your specific purpose then you can demand a refund if it isnt. Whether that will run in practice is another question, but it often does.

NT

[meow2222]

I wouldnt recommend this to someone with little electrical knowledge as the gotchas are so easy to miss. Also it only partially addresses the problem.

If theres an RCD, the supply will trip if 30mA flows, and the wire could be connected to a rained on wall etc to get 30mA.

With no RCD, if the lamp lights we know the wire can sink 1/4A, but again that doesnt imply it will sink a few times the fuse rating, ie well over 10A, which is necessary to break the supply in a fault with an older installation, or a newer split CU with no RCD on lights.

Finally it can make all sorts of unexpected objects live, thus represents a danger to the novice. This is why I just didnt answer. The best solution is a plastic fitting imho. Not an unearthed metal double insulted one, which wont really be safe in outdoor conditions.

NT

[manatbandq]

There's no evidence the OP explained that his specific purpose was to use a light requiring an earth in a location where there is no earth available. In the absence of such, the light must be deemed to be fit for it's intended purpose.

If I choose a light fitting and pay for it with no other interaction with the store staff, can I demand a refund if I later realise it's not suitable for use in Zone 1 in a bathroom? No, because the fitting is obviously suitable for it's purpose (ie it's designed and sold for use in other zones) but there is a mismatch between that and my desired purpose.

Obviously, many shops _will_ give a refund and we should praise them for that but I do not think there is any legal right in this case.

MBQ

[Dave Plowman (News)]

I sort of assumed no RCD reading between the lines.

It's a pretty unlikely scenario - an earth that will light a bulb but not be correct elsewhere, although I grant it's just possible.

That's why I added the note in brackets.

The best solution would be to have the earth tested properly. If it's faulty others in the house may be too. But a plastic fitting addresses the immediate problem. That's why I supplied a URL for a supplier.

[Kroma]

An update:

I still haven't been able to get to my Dad's to take the current light off the wall but he has just told me that he is *certain* that there is no proper earth wire leading to the current light and that the earth lead

*from* the light is attached to a screw in the wall.

The current light is also metal!!! Eek!

However, he has also told me that there is an RCD fitted to the house's electricity supply. He believes that this was fitted when an electric shower was installed.

Does this make any difference?

Daz

PS If all is no good, the back of the receipt (B&Q) states that there is a

28-day money back guarantee if unused.

[Owain]

I'm afraid I would be inclined to run a new earthed cable and not bodge about relying on plastic fittings, especially outside.

Do you love him, or would you rather have the inheritance?

Not necessesarily, quite likely the shower was installed to a new mini-CU with MCB and RCD for the shower only, not protecting the rest of the installation.

Owain