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.

 

[SJD]

The earth on the incoming cable(s) may not actually be connected to earth, but could be floating somewhere between 0 and 240V depending on the loading. If you are going to connect the earth to the fitting, you need to be sure the incoming earth actually is connected to earth, otherwise you would be leaving the fitting as potentially dangerous.

You can test this - with the power to the installation turned off - for example with the aid of a long lead back to the main earth terminal and a multi-meter set to measure Ohms.

I also agree that with the wiring as photographed, it should not be class II - you have single insulated cables inside the ceiling rose, that might touch the metal casing - and if you accidentally caught one e.g. by a sharp edge or screw, it could pierce the insulation. It is difficult to install it to meet class II with the loop in/out extra wires, unless you also double insulate these and the connector block.

 

[123]

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.

Apologies but from the offset I have felt this is a windup. We have what now appears to be a Class II fitting, with a now doctored earth point. The instrument of choice to check all of this is a Volt Stick...

The OP has some electrical knowledge, and at the end of the day it's merely a light fitting. It's Class II according to manufacturer, if you disagree take it up with them.

Someone in auto sparking will at the very least have a multi metre, not my instrument of choice, but far better than a Volt Stick.

Maybe you should look at all of the posts rather than one in particular though. I still feel its a windup, and still to see good reason as to why anyone would butcher a light fitting.

On this thread, I'm out

 

[Deleted member 9648]

Metal class 11 fittings are very common now and are a real headache with UK wiring systems. They are only practical with one twin cable present which can be terminated in the block provided without any exposed basic insulation. When faced with these I have either terminated the cables in the void above the fitting if accessible and dropped a short twin flex into the fitting,or done as the OP has done and earthed it.

edit.....re-the above post I cant see that connecting an earth to the bracket has in any way 'butchered' the fitting?

 

[drevyluk]

I just wanted to thank everyone for their help.

I've dug out my multi-meter and it's confirmed there is nothing at all wrong with the light fitting.

Clearly I've made an amateur mistake assuming that a cheap mains voltage tester is up to the job while some of my tools were boxed up, it's been binned and lesson learned.

The entire wiring in the property is both new and certified, so hopefully I can assume the earth works as intended and safely earth the fitting without additional testing.

I am checking with the local building control to see if I need a minor works certificate under Part P regulations. I have a qualified electrician coming out to run a 20 Amp cable to the cooker point soon anyway and can get him to perform any additional testing if needs be.

Thanks again for taking the time to look over this and point me in the right direction.

 

[westward10]

Metal class 11 fittings are very common now and are a real headache with UK wiring systems. They are only practical with one twin cable present which can be terminated in the block provided without any exposed basic insulation. When faced with these I have either terminated the cables in the void above the fitting if accessible and dropped a short twin flex into the fitting,or done as the OP has done and earthed it.

edit.....re-the above post I cant see that connecting an earth to the bracket has in any way 'butchered' the fitting?

Totally agree and as he has used taped up block connector as opposed to a suitable insulated enclosure he did the right thing by earthing it.