Earth to Neutral Continuity - Advice Needed

[Conan The Librarian]

Hi all.

Reasonably competant non electrical engineer homeowner here. I have a question for the experts:

I recently replaced a horrible above-ceiling downlight connection with a proper Hager junction box. Whilst checking things generally I found my multimeter was reading a continuity between neutral and earth on one side of the lighting circuit loop. This was with the circuit isolated at the board obviously.

What's going on here? Is this indicative of a fault? I'm reluctant to turn the circuit back on as it feeds some suspended metal track lighting in the lounge.
Advice would be welcomed.
Thanks

 

[timhoward]

You would see this if your house has TN earthing (like many do).
Turning off an MCB wouldn't isolate the neutral, so strictly speaking the circuit isn't properly isolated.

If you turn off the main switch of your consumer and you observe that there is now no continuity, then this proves it is the supplier-side link between N and Earth that you are measuring, and it doesn't constitute a fault.

 

[Conan The Librarian]

Hi all.

Reasonably competant non electrical engineer homeowner here. I have a question for the experts:

I recently replaced a horrible above-ceiling downlight connection with a proper Hager junction box. Whilst checking things generally I found my multimeter was reading a continuity between neutral and earth on one side of the lighting circuit loop. This was with the circuit isolated at the board obviously.

What's going on here? Is this indicative of a fault? I'm reluctant to turn the circuit back on as it feeds some suspended metal track lighting in the lounge.
Advice would be welcomed.
Thanks

You would see this if your house has TN earthing (like many do).
Turning off an MCB wouldn't isolate the neutral, so strictly speaking the circuit isn't properly isolated.

If you turn off the main switch of your consumer and you observe that there is now no continuity, then this proves it is the supplier-side link between N and Earth that you are measuring, and it doesn't constitute a fault.

Thanks for the advice!
I just did as you suggested, and after turning off the main switch the continuity disappears. So it seems all is well, and I'm grateful for your help.

I'll now go and educate myself about different earthing systems. One thing I don't understand though is how an earth to neutral connection can be safe. If you were to touch an earth bonded metal object, are you not effectively touching a conductor that has an electron flow whizzing through it?

 

[timhoward]

I'll now go and educate myself about different earthing systems. One thing I don't understand though is how an earth to neutral connection can be safe. If you were to touch an earth bonded metal object, are you not effectively touching a conductor that has an electron flow whizzing through it?

This is an excellent video that will probably tell you all you want to know, and more:

 

[Conan The Librarian]

Every day's a school day - brilliant video!

 

[oscar21]

Thanks for the advice!
I just did as you suggested, and after turning off the main switch the continuity disappears. So it seems all is well, and I'm grateful for your help.

I'll now go and educate myself about different earthing systems. One thing I don't understand though is how an earth to neutral connection can be safe. If you were to touch an earth bonded metal object, are you not effectively touching a conductor that has an electron flow whizzing through it?

Yes you are touching a live cable that has 230v wizzing through it exactly the same as if you touched the live wire, its just that there isn't a flow through you because the neutral is earthed, so the difference between N-E is 0V.

 

[Conan The Librarian]

Yes you are touching a live cable that has 230v wizzing through it exactly the same as if you touched the live wire, its just that there isn't a flow through you because the neutral is earthed, so the difference between N-E is 0V.

Several years ago I noticed that by moving my finger tips lightly over the metal cases of mains powered appliances, I can detect if they are switched on or off. This includes lamp stands and the top of my MacBook that I'm typing this message on.

If the appliance is disconnected it feels smooth. If it's turned on, the surface has a different feel - slightly rough and buzzy, as if I'm feeling a micro current in my fingers. Only works if you move your fingers though. There must be a technical explanation for this, and I'm thinking it's related to the topic above. I'm also wondering if anyone else has noticed the same, or if I'm just a freak of nature...

 

[DPG]

Several years ago I noticed that by moving my finger tips lightly over the metal cases of mains powered appliances, I can detect if they are switched on or off. This includes lamp stands and the top of my MacBook that I'm typing this message on.

If the appliance is disconnected it feels smooth. If it's turned on, the surface has a different feel - slightly rough and buzzy, as if I'm feeling a micro current in my fingers. Only works if you move your fingers though. There must be a technical explanation for this, and I'm thinking it's related to the topic above. I'm also wondering if anyone else has noticed the same, or if I'm just a freak of nature...

Yes, this is leakage current due to filter capacitors connected between live, neutral and earth. Not dangerous - the current available is tiny.

Obviously you don't get this on appliances where the metal case is earthed.

 

[oscar21]

The best one is when people that are fault finding don't understand this and the first circuit they check has a live-earth fault because all the neutrals are still connected. They spend hours looking for a fault on that circuit that doesn't exist.