Advice, please

Mike Smith01 · Dec 5, 2024

Our stairs has a light at the bottom of them and a light at the top. The two lights are not independent of each other but there is an upstairs switch and one downstairs. So the lights can be turned on or off from either switch. I've recently found there is a current going through the earth of this group of lighting. I've checked the lights and the switches are wired correctly, they seem fine but I'm no electrician, I just have basic knowledge.
I've changed the switches for new ones but the current is still passing through the earth. The only thing I haven't tried yet is changing the bulbs or light fittings, but as I said, the wiring for them looks correct.
Anything else I could check myself before I have to get an electrician in?
Thanks

ProDave · Dec 5, 2024

How did you determine there was "current going through the earth"? Clearly it is not fed from an RCD protected circuit then?

Mike Smith01 · Dec 5, 2024

ProDave said:
How did you determine there was "current going through the earth"? Clearly it is not fed from an RCD protected circuit then?

I have a multimeter.
Yes we had a new RCD unit fitted about 2 years ago when our electricity meter was moved from inside the house, to an electrical box on the outside of the house.

binky · Dec 5, 2024

What sort of figures are you getting, and why were you even looking?

All cabling will induce voltages in the earth, you may just be seeing that

Fleeting · Dec 5, 2024

Where are you measuring this live to earth?

SPECIAL LOCATION · Dec 5, 2024

Mike Smith01 said:
Our stairs has a light at the bottom of them and a light at the top. The two lights are not independent of each other but there is an upstairs switch and one downstairs. So the lights can be turned on or off from either switch. I've recently found there is a current going through the earth of this group of lighting. I've checked the lights and the switches are wired correctly, they seem fine but I'm no electrician, I just have basic knowledge.
I've changed the switches for new ones but the current is still passing through the earth. The only thing I haven't tried yet is changing the bulbs or light fittings, but as I said, the wiring for them looks correct.
Anything else I could check myself before I have to get an electrician in?
Thanks

Mike Smith01 said:
I have a multimeter.
Yes we had a new RCD unit fitted about 2 years ago when our electricity meter was moved from inside the house, to an electrical box on the outside of the house.

What made you even think about trying to measure anything on the earth?
What was NOT working that made you start your investigations?

How are you actually measuring this current ? (or are you measuring a voltage?)
i.e. where area the meter probes and what setting is it on ?
Ohms / AC voltage / AC current / DC voltage / DC current ?

My gut feeling is that you don't actually have any current anywhere...
you are just reading an induced voltage from either the feed or a strapper wires between the switches.

If the RCD CU was fitted and tested correctly 2 years ago, then the RCD would be tripping as soon as it detects a 30ma fault current in any of the earths..

I would never recommend changing any random parts during any fault investigations..
All it does is waste time and money..

Its far better to do correct testing and verify which part(s) is/are working and which part(s) is/are not..
Then fit replacements of known faulty items.

Richard-the-Ninth · Dec 5, 2024

@Mike Smith01 The average "DIY Multi meter" is high impedance, which in turn means that it can easily read "induced voltages" You will often get an induced voltage (also called ghost voltage) when you have a light(s) controlled by two switches (Typically on a landing, this is called two-way switching)
An electrician would use his Multi-function Tester (MFT) which has a low impedance and will not see the voltages you are seeing, also an MFT is made to be used on mains voltages, it has inbuilt protection that the average multimeter doesn't have, also the test leads on an MFT are made to a higher standard and also offer more protection should anything go wrong. (There is more to it, but that is a summary)

You really should not use an average multimeter on mains electricity, yes you can use it to figure out how a (not connected to anything) switch works, or does the switch on that gadget work, and yes they are great for electronics (What they were designed for) but keep it away from the mains, as we would all like to see you post again another day.

Nicky Tesla · Dec 5, 2024

If you used a volt stick and found the accessory screws to show up as live, there is probably no continuity back to the earth terminal back in the ccu. There will be a break somewhere.

UNG · Dec 5, 2024

Nicky Tesla said:
If you used a volt stick and found the accessory screws to show up as live, there is probably no continuity back to the earth terminal back in the ccu. There will be a break somewhere.

I wouldn't be relying a volt stick on the accessory screws to defintively tell me there is a voltage on the earth a single point voltage tester or neon screwdriver would be more useful

Nicky Tesla · Dec 5, 2024

I’m merely wondering how the thread poster come to realising there was a problem with voltage/current on the earth.
P.S. don’t knock volt sticks they are a very useful tool, I would not be without one.
A good tip for you. When tracing the cause of a nuisance rcd tripping, they are brilliant for finding where a nail has caught a cable embedded in a solid wall as the volt stick often thinks the wall is live within a foot or so from the nail.

UNG · Dec 6, 2024

Nicky Tesla said:
I’m merely wondering how the thread poster come to realising there was a problem with voltage/current on the earth.
P.S. don’t knock volt sticks they are a very useful tool, I would not be without one.

I don't recall knocking volt sticks they have their uses many people diss neon screwdrivers but they do have their uses

Nicky Tesla said:
A good tip for you. When tracing the cause of a nuisance rcd tripping, they are brilliant for finding where a nail has caught a cable embedded in a solid wall as the volt stick often thinks the wall is live within a foot or so from the nail.

A tip for you a good tone tracer puts you right on the nail head

Nicky Tesla · Dec 6, 2024

Thanks for the tip, but nails are not hard to find as they usually have a picture hanging off them.

UNG · Dec 6, 2024

Nicky Tesla said:
Thanks for the tip, but nails are not hard to find as they usually have a picture hanging off them.

Not always as I found out on a couple of CU swaps a few years back, the nails had broken and the holes had been filled and papered over to leave a hidden developing fault in the wall

Nicky Tesla · Dec 6, 2024

Ye I’ve found them too. A strong magnet from a magnaclean is good at finding those and the nails in plasterboard.

michael8554 · Dec 6, 2024

My Fluke volt stick thoroughly confused me when my EVSE stopped working, showing volts all the way.
There was in fact a poorly connected Wago that was charred as a result.
Not enough volts for the EVSE but enough for the stick.
But a useful tool nonetheless.

Advice, please

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