Retrofitting earth wire to light socket

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mdf

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#251731 9-Jul-2019 13:23

I bought a Yeelink ceiling light from PB Tech over the weekend sale. The instruction manual states that an earth connection is required. Unfortunately the relevant ceiling socket and switch (unsurprisingly) has only two wires at each.

I watched the installation video on PB's website prior to purchasing, and that video only has live and neutral (no earth) so I thought I would be fine until it actually arrived.

I need to get an electrician in for some other work anyway, but wasn't planning on doing so for a couple of months while I wait for other things to fall in to place. I appreciate nothing in life is certain, but hoping for a steer as to whether adding an earth wire to a light socket is (a) relatively simple and straightforward (i.e. keep the light and wait for electrician to install) or (b) long, complicated and/or expensive (i.e. return the light).

I suspect some of this may relate to whether or not the earth wire also needs to connect to the switch, or if it is okay just to earth the light socket. Access in the roof above the relevant light is okay (if not great - apprentice work), but I suspect that if the earth wire needs to be pulled down to the switch that there will be further complications (I had a nightmare using some existing cat5 as draw wires for an ethernet cabling project. Why would you tie a knot in ethernet cabling!?)

frankv

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#2272391 9-Jul-2019 13:53

Complexity and cost will depend a lot on your house construction, where the light socket is, and where an earth connection is available. What's needed is to run another wire to the socket, probably from the switchboard.

The purpose of the earth is to save you from getting electrocuted if there is a fault that connects mains power to the metal parts of the light fitting, and you touch the frame.

I am not an electrician. I'd probably just leave the earth off.

sbiddle

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#2272401 9-Jul-2019 14:15

In many older NZ properties (and by old I'm only meaning 15+ years) it is also really common to wire lights so the neutral runs straight to the light fitting and the wall switch just switches the phase.

Rikkitic

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#2272403 9-Jul-2019 14:20

With light fittings in particular, earth connections are often pointless. If the fitting has a metal component and says an earth is needed, it is better to have one than not, but often it doesn't actually do anything. Any metal bits on a light fitting should not have any kind of electrical connection to either of the two power leads. Those should only connect to the light bulb itself. So under almost any conceivable normal circumstances, any metal bits should never be able to become live.

If some kind of unlikely manufacturing fault does connect an exposed metal part to one of the power leads (phase or neutral), this would be a very bad thing but it might go unnoticed for years. If the light is wired correctly (usually the case, but not always), the phase side is the one that gets switched, so any time the light is off, there would be no power on any metal bit, even if it was connected. But you might die if you tried to change the bulb with the switch on. If there was a fault that connected the metal to the neutral side, you would probably be okay unless you somehow managed to touch a live connection from somewhere else while also touching the metal. This is extremely unlikely.

There is a difference between old wiring without RCD protection where earth is connected to neutral, and newer wiring that does have RCD. In both cases you are very unlikely to be electrocuted by a light fitting. It is not something I would stay awake over.

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Bung

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#2272427 9-Jul-2019 15:16

1. the usual disclaimer IANAE(lectrician)

2. In my experience light fittings are more likely to be a source of electric shock than other fittings. The sockets are often loose or broken and the action of twisting a bulb winds up the wiring. Live phase at a common point at the fitting is not just an old thing. Some electricians still do it on new work. You have to switch off at the breaker or fuse to be certain. New lighting points must have an earth available. Sometimes it may be there but not connected through. If you have to retrofit the earth has to go back to the board.

nickb800

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#2272429 9-Jul-2019 15:27

Not sure if referencing another forum adds credibility , but https://www.electricalforum.co.nz/index.php?action=more_details&id=1351803544

It says that a 2.5mm2 stand alone earth back to the switchboard is suitable, don't need to go via the light switch

Bung

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#2272573 9-Jul-2019 18:33

Several of the frequent contributors to that forum are on the NZ technical committee for the electrical standard AS/NZS 3000. Often the advice is more correct than the Energy Safety site.

elpenguino

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#2272669 9-Jul-2019 22:54

That's from my 2008 copy BTW.

Earths are safety devices so you should be thinking 'I need this' unless the regs say otherwise.

I thought I had seen a reg that allowed you to have no earth if the fitting was over a certain height but I'm buggered if I can find that reference to it.

If you do need to run an earth, I'm sure a sparkie will know the easiest / cheapest way to comply with the regs e.g. running to the nearest hot point or whatever is allowed.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

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Yogi02

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#2272718 10-Jul-2019 01:29

All of the above is correct.

I would be wiring it with just the neutral and the phase from the existing fitting. (fuse off, of course)

When you eventually get the sparky in, get him to check it out and run an earth if you decide it's needed.

richms

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#2273802 10-Jul-2019 10:47

Friend had the same thing with their place when changing the 1950's recessed fluros to downlights. The end result was that a new earth had to be taken all the way back to the board to the first one in each group and then standard twin and earth between them. The sparky that he used from his work was more an industrial guy and wasnt happy with the idea of joins in the earth between the board and each group of lights so they ran several of them. I think they ended up using really thick stuff because that is what they could "aquire" easily.

Richard rich.ms

sir1963

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#2275492 12-Jul-2019 19:28

sbiddle:

In many older NZ properties (and by old I'm only meaning 15+ years) it is also really common to wire lights so the neutral runs straight to the light fitting and the wall switch just switches the phase.

"loop at light" is/was a bad idea, all that heat making the cables brittle.

It also takes longer to do the connections at the light from a ladder than down at the switch (Loop at switch).

LEDs remove the heat issue

However adding extensions with loop at light are easier, and if you have 6 switches on one plate is is a LOT less crowded but this situation is rare in domestic wiring

I have 99% of the time done loop at switch.

I also used T&E (Twin and Earth) just in case the owner wanted to change the light fittings to one that required an earth.

The one who REALLY P$$D me off were the ones who only left short tails at the light so when the wiring cooked its self it was almost impossible to fix, and I have been forced to rewire lighting circuits because of some tightwad sparky who was shaving a few cents on wire.

And yes, I am a registered sparkie though I have not done house wiring for 30 odd years.

sir1963

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#2275493 12-Jul-2019 19:32

elpenguino:

That's from my 2008 copy BTW.

Earths are safety devices so you should be thinking 'I need this' unless the regs say otherwise.

I thought I had seen a reg that allowed you to have no earth if the fitting was over a certain height but I'm buggered if I can find that reference to it.

If you do need to run an earth, I'm sure a sparkie will know the easiest / cheapest way to comply with the regs e.g. running to the nearest hot point or whatever is allowed.

Yeah IIRC if it was over 2M high, If I could find my regs book ( 1976 ?) I would look, or I could go back to my copy of the regs from about 1923 that I found in a 2nd hand book shop

pipe60

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#2275665 13-Jul-2019 09:23

You don't need a earth at the switch. Normally an easy job to run an earth back to the switch board(2.5mm). If your lucky you might even find a J box in the roof with a earth in it. If the fitting needs an earth its best to run one for it.

insane

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#2275703 13-Jul-2019 10:22

I'm surprised the new unit is not double insulated. Will have a small logo of a square inside of a square on the certification label. But yes running an earth wire from the fitting to the fuse board or another lighting earth point is the advise I got from my mate who's a sparky.

Tracer

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#2276443 14-Jul-2019 18:04

pipe60:

If your lucky you might even find a J box in the roof with a earth in it.

Do not use the protective earth from a cable associated with another subcircuit. That's basically setting a trap if anybody happens to be removing that subcircuit at a later date. It contravenes 5.5.2.2.1 of AS/NZS 3000:2007:

5.5.2.2.1 Circuits

The protective earthing conductor for a circuit that is incorporated in the same cable sheath or wiring enclosure as the associated live conductors for the circuit shall only be used for the earthing of equipment supplied from the circuit.

Exception: This does not preclude an unenclosed common protective earthing conductor being used for a number of different circuits.

gregmcc

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#2276463 14-Jul-2019 18:47

AS/NZS300 say if you are going to add an earth wire to an existing circuit that doesn't have one, it must be run back to the distribution board and it must be at least 2.5mm2.

Should a home owner choose to do it themselves, it must be checked by an inspector (not an electrician) an the home owner cannot put the wire in the distribution board, this must be done by an electrician, or the inspector checking the work