No voltage on live-neutral but voltage on live-earth

[Ellsa100]

Hi there

I recently replaced the downlight fittings in my bathroom so they are now GU10 LEDs (previously they were MR16s). The lights are IP65 and connected to a 30mA RCBO.

The light was working fine until recently. I was fiddling with the light fitting to correct the ceiling which had been damaged in the swap over - which involved taking out the fitting and replacing it - and now the LED isn’t working. I used a multimeter to check the voltage and there is 240v between live and earth but 0v between live and neutral. It seems like the neutral has been disconnected somehow.

The wiring is difficult to access as It is in the ceiling void - so it would be tricky to figure out the issue with the neutral wire. Would it be OK to use the earth wire to complete the circuit given thedownlight is double insulated?

thanks!

 

[buzzlightyear]

When I explained my original issue to a builder (who holds himself out as a qualified electrician) - that on the downlight that wasn't working there was a voltage between Live and Earth but no voltage between Live and Neutral - it was his suggestion that I use Earth instead of Neutral to complete the circuit.

what right minded spark told you that ,or i sould say a clown spark .

 

[stevethesparks]

Get a qualified electrician in

 

[telectrix]

Think I've heard it all now.......By the way anyone know if I can use the gas pipe for my shower feed?

only if it's a gas shower.
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what right minded spark told you that ,or i sould say a clown spark .

OPsaid a builder told him... nuff said.

 

[buzzlightyear]

Think I've heard it all now.......By the way anyone know if I can use the gas pipe for my shower feed?

only if it's a gas shower

wow ,whistling shower ,quick patient it and get it on dragon death .lol .

 

[pc1966]

3. I assume running an earth loop impedance tester to check earthing of devices in my house is something left to the experts (i.e. I shouldn't buy a device off eBay and do it myself)!?

If you are doing live testing on a high energy system (like the mains, where you have the prospect of a massive fault current) you really want to know that your equipment is safe and not going to explode in your face if something goes wrong. Buying stuff of eBay, more so if you do not know exactly what you are doing, is not a route to that goal.

The typical Multi Function Tester that would do this is in the £500-1000+ price range when new, so even 2nd hand (if working...) is going to be more expensive than getting a sparky in to do the work.

4. Last stupid question...why can't you just use a regular multimeter reading to check the voltage between a Live and Earth wire to check if it is grounded (i.e. if it reads 240v, it is presumably grounded, if it reads 0v, it is not)?

It is not a stupid question, in fact it is a subject that often catches out trainee electricians and similar. A typical digital multimeter has an impedance of 10M ohm, so to get a reading of 240V when the supply is 241V (a difference most would ignore as implying any sort of error in the circuit) only needs 24uA through the meter.

If the impedance to the real 0V point is less than 41.7k ohm you won't see anything wrong. Depending on how a cable is used and any interference filters connected to it, etc, you can get comparable levels of current flowing between insulated conductors via capacitance.

But if there really is a fault then 41.7k will only cause 5.8mA to flow, that will not trip any normal (domestic) protection system. But then the metalwork is live and if someone were to touch that and another potential they may get a serious or fatal shock.

Also you must remember that a 30mA RCD is there to provide "additional protection" and you don't really want to rely on it saving your skin as the 1st defence. RCDs have much higher complexity that then typical MCB over-current trip that ought to go in a fault and so a higher chance of failing, also most folk do not regularly test them (using the test button) so any fault could be present for years. Even a non-fatal shock can lead to serious or even fatal injuries if, for example, it leads to someone falling off a ladder.

 

[Ellsa100]

thanks very much for your comments. i'm gonna get a registered electrician in to look at things. May also get a once over for all the wiring for peace of mind too, but i do appreciate learning things (and need to know my limitations lol).

 

[GBDamo]

When manoeuvring the one light fitting you have moved the cables.

This in turn has highlighted a poor termination at elsewhere that has failed.

Two things a proper electrician would have ensured.

1, All terminations are secure.

2, Where practicable cables are clipped so as to relieve stresses.


How many of these lights are in this room?

How many are still working?

There's a good chance the loose neutral lies in the last working fitting = easy fix, or in a junction box = pain in the proverbial.

 

[Ellsa100]

When manoeuvring the one light fitting you have moved the cables.

This in turn has highlighted a poor termination at elsewhere that has failed.

Two things a proper electrician would have ensured.

1, All terminations are secure.

2, Where practicable cables are clipped so as to relieve stresses.


How many of these lights are in this room?

How many are still working?

There's a good chance the loose neutral lies in the last working fitting = easy fix, or in a junction box = pain in the proverbial.

Thanks - there are 5 lights in the bathroom. 4 lights are not working. OMG you made me realise what is wrong with the circuit!!!! I checked the one light that is working - and the other lights are working parallel off that - and the neutral there had come out. Hey presto!!!!!!!!!! pushed the neutral back in and now all 5 lights are working. thank you so much!!!
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Thanks - there are 5 lights in the bathroom. 4 lights are not working. OMG you made me realise what is wrong with the circuit!!!! I checked the one light that is working - and the other lights are working parallel off that - and the neutral there had come out. Hey presto!!!!!!!!!! pushed the neutral back in and now all 5 lights are working. thank you so much!!!

I find the junction boxes can get so busy with wiring that wires can flick out of their termination points when you try to squeeze everything in....

 

[telectrix]

I find the junction boxes can get so busy with wiring that wires can flick out of their termination points when you try to squeeze everything in....

that's why wagos are best thing since inside bogs.

 

[Ellsa100]

I find the junction boxes can get so busy with wiring that wires can flick out of their termination points when you try to squeeze everything in....

that's why wagos are best thing since inside bogs.

I'm tempted to go round putting the original junction boxes - which seem way more secure and spacey - than the small ones that came witht he light fittings, just to stop this issue happening again.

 

[telectrix]

I'm tempted to go round putting the original junction boxes - which seem way more secure and spacey - than the small ones that came witht he light fittings, just to stop this issue happening again.

even better, use wagoboxes and wagos.

or maybe click connectors.

https://cpc.farnell.com/c/cable-leads-connectors/connectors/click-connectors/click-flow-connectors

View: https://www.youtube.com/watch?v=DDoxf4Yxq2s

 

[snowhead]

Ask the "Qualified Electrician" what effect using Live and Earth for the light will have on the RCBO for that circuit.

And politely suggest to him that he removes the Phrase "Qualified Electrician" when describing himself and just keep to Builder, for which there are no formal qualifications.

 

[HappyHippyDad]

I find the junction boxes can get so busy with wiring that wires can flick out of their termination points when you try to squeeze everything in....

You do love your wago's don't you Tel
I'd have to agree though. I started electrics at around the time wago's were coming out so that's what I've mainly used. However, I come across screw junction boxes all the time and by golly they're a pain in the backside when you've got a few cables to get in.
The screw/bolt often doesn't go in straight.
It can take bloody ages.
Terminations come loose over time.
The lids often seem to be broken or not attached well.
Holes in the side where they have not been fitted properly.
If there's a few conductors in one terminal you're not completely sure they are all in properly as it's a right jumble.

On the plus side, on the very rare occasion when you have to hide a connection under a kitchen wall cabinet they come in handy

 

[KennyKen]

The OP clearly has DIY by their name which justifies asking this type of question.

Right ok, Next we’ll have someone asking about a Flux capacitor. I know it’s got DIY by her name mate. But sometimes I often wonder the legitimacy of these posts.
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How childish a dislike... Opinions differ. Maybe Chris has a point about soft women on this site.

 

[James]

I have given out over 2000 likes and agrees
Just 12 dislikes.
I have no interest in getting in a debate about it but I do actually dislike the post.