Live Light Fitting?

[drevyluk]

Hi,

I'm a little perplexed by a simple light fitting replacement that has turned unexpectedly interesting.

Replacing the fitting I linked the loop to a junction block and sealed it with insulation tape (as the new fitting didn't have any connectors as standard. I connected the live and neutral as normal and as there was no earth on the metal light fitting I connected the earth to it (with a screw and washer, basic but serviceable).

Upon switching the lighting circuit back on the light comes on as expected but my pen mains voltage tester seems to think the metal casing is live.

I've crawled into the loft just to make sure I didn't screw into any cabling when re-mounting the fitting and that seems all fine.

Am I doing something incredibly stupid or does it appear that the earth for this loop is live somehow?

I am an amateur and so any help would be extremely gratefully received.

 

[123]

Has to be a windup surely?

 

[drevyluk]

I wish it was ...

Is there something incredibly obvious, or stupid I've done?

 

[123]

Still think it's a windup...

But why butcher a light fitting by adding an earth point to it when manufacturer didn't add anything for it.

And why use a silly Volt Stick to try and determine that is was live.

 

[drevyluk]

The basic reason is that, not having any qualifications in mains housing electronics but being familiar with vehicle electronics I'm concerned about any un-earthed metal unit that is accessible externally. Like the casing.

I got the voltage pen tester to follow through with the above paranoia. As I'm not 100% certain of what I'm doing I'd rather be over cautious than otherwise.

It's why I have come here looking for assistance. Which I would be grateful of.

 

[snowhead]

Was The "Earth" wire you connected, in use on the old fitting?

Have you got a picture of the new fitting, it would be unusual for a metal fitting Not to have an earth connection.?

 

[123]

If used to vehicle electronics you are bound to have a multimeter ... better to use that to test than a volt stick but still not ideal.

You haven't by any chance nipped a wire when you installed your earth point to the fitting? Where did you buy this fitting from?

 

[Darkwood]

Still think it's a windup...

But why butcher a light fitting by adding an earth point to it when manufacturer didn't add anything for it.

And why use a silly Volt Stick to try and determine that is was live.

It appears as has been implied that the OP has limited knowledge in domestic electrics and has used some possible knowledge of automotive electrics that has given him some misguided confidence to dabble in household electrics, your comments are not helpful so please either try to help the OP out or don't comment further.
Maybe you could explain the dangers of the actions he has done and the issues of relying on volts sticks to verify the prensence of voltage.
Its clear the OP isn't an electrician so its understandable he will not be clued up on these matters.

 

[Richard Burns]

If the metal light did not have an earth terminal then it may be a class II piece of equipment and would be marked with this symbol.

If this is the case then an earth is not required.
A voltage tester pen could well pick up the power cable as well as the casing.
You would need to do contact testing with a two pole voltage tester, but there are risks inherent in this if the casing is actually live.
Get access to test points whilst the power is completely off, preferably by switching off the main house switch, then test without exposing yourself to danger.

 

[drevyluk]

See attached image of wiring.

There are two neutral coloured wires going into the sleeve entering light fitting junction box but the installing electrician has marked one up with a brown live sleeve, it's just not visible on the image.

I do indeed have a multi-meter but to be honest I'm right in the middle of moving (and decorating the new house) so it's in a box somewhere.

The previous fitting was a bog standard plastic one and the two earth cables were just fitted to a junction marked earth on that one.

The fitting was a Dunelm Mill one.

 

[drevyluk]

It is indeed a class II unit. It mentioned that in the instructions.

 

[Darkwood]

It is indeed a class II unit. It mentioned that in the instructions.

The fitting been classII would not require an earth, what makes me uneasy about this is the fact that the metal mounting bracket would not be affording double insulation against your connecting wirescoming through the ceiling, the fitting integral wiring will have 2 layers of insulation afforded to it thus not needed earthing but it depends if your fitting mounts to that ceiling bracket with plastic or metal - I see a poor designed fitting if this is the case and would leave the earth as you have done. Can you post a pic of the whole fitting.

 

[drevyluk]

Hi,

Please see picture of external of light fitting. It does indeed connect directly to a metal external casing without any additional protection. This is the main reason I was concerned and attached the earth directly.

I was careful not to cut into the insulation of any of the wiring when replacing the fitting, though I absolutely accept it is possible to have done so without being aware of it.

Am I detecting that mains voltage testers are unreliable? Not a surprise at the price.

I very much appreciate the advice and assistance being offered.

 

[Darkwood]

In my opinion the manufacturer has got it wrong which is scary, the top bracket and cup need earthing due to the single insulated joints it contains but as the copper/brass metal shade is classII insulated then no need to earth the shade.

 

[drevyluk]

In my opinion the manufacturer has got it wrong which is scary, the top bracket and cup need earthing due to the single insulated joints it contains but as the copper/brass metal shade is classII insulated then no need to earth the shade.

Understood. I'll leave the earth in place then, be even more suspicious of cheap light fittings in future, lol, and dig out my multi-meter to double check the cup and bracket as it's almost certain the pen is giving me a false reading?