Light switch mounting box has no earth terminal/screw.

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Hi,

I am replacing all the light switches in my house from metal switches to plastic ones. All the mounting boxes are metal.

I have a couple which have no earth terminal or screw but all the cable is two core and earth.

What should I do with the earth cable? Some people have said I should tape it off, others say I should try to connect it to the mounting box. Any suggestions of how to do this?

Here is a photo .... http://i.imgur.com/kuRtW.jpg

Look forward to your responses.

Nick
 
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Don't use tape. It comes unstuck after a while.

Put the loose earth conductor in a small piece of insulated "choc block".

You'll need the smallest one as that box is very shallow.
 
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Don't use tape. It comes unstuck after a while.

Put the loose earth conductor in a small piece of insulated "choc block".

You'll need the smallest one as that box is very shallow.

Thanks for your reply. Is it not worth hooking the earth around one of the little hooks in the corners of the box? There are two small hooks of you can see?
 
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It looks like that particular K/O box has nylon lugs, so it doens't *have* to be earthed, however as you have an earth bext to connect it. I usually drill and tap a hole in the back of the box (taped to M4 works well), crimp an eyelet crimp on the earth, clean the paint from round the hole and attach with suitable machine screw

Looks like there is some degraded di-isoctyl phthalate (the green liquid) on that cable, the plasticiser in the PVC is breaking down through contact with the copper, its a known issue on late 60's early 70's cable... it will eventually be necessary to re-wire the installation, the amount you have there though is small, so you should clean it up (wash hands afterwards, it can cause sickness and may be linked to longer term fertility issues), a periodic inspection of the installation might be advised, this should give an indication of the severity of the issue and whether its affecting insulatation resistance
 
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It looks like that particular K/O box has nylon lugs, so it doens't *have* to be earthed, however as you have an earth bext to connect it. I usually drill and tap a hole in the back of the box (taped to M4 works well), crimp an eyelet crimp on the earth, clean the paint from round the hole and attach with suitable machine screw

Looks like there is some degraded di-isoctyl phthalate (the green liquid) on that cable, the plasticiser in the PVC is breaking down through contact with the copper, its a known issue on late 60's early 70's cable... it will eventually be necessary to re-wire the installation, the amount you have there though is small, so you should clean it up (wash hands afterwards, it can cause sickness and may be linked to longer term fertility issues), a periodic inspection of the installation might be advised, this should give an indication of the severity of the issue and whether its affecting insulatation resistance

Thanks for this reply and your observations. I didn't notice that green but that is quite worrying. I will get it checked when my electrician visits next and consider the options - hope it doesn't need a re-wire! That would be pretty annoying!!
 
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Its likely the new 3.5mm screws that come with your new switches are a different thread to the old boxes, have you tried them yet.

If you keep them boxes then you may need to reuse the old manky screws.

If they are different thread then now may be the ideal time to change the boxes
 
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