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Topic Title: Lighting circuit without an earth
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Created On: 18 March 2013 09:33 AM
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 18 March 2013 09:33 AM
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ebanner

Posts: 48
Joined: 18 January 2003

Hi

I have a 1964 lighting circuit which does not have an earth. I want to replace the light switches as some of them look old and worn. There is just a wooden box behind the switch which raised countersunk screws go into. You can get plastic caps that fit over the screws so was thinking of doing this to make it Class II. Does anyone have any ideas. I don't want to rewire as the wiring is good for another 50 years!

Ed
 18 March 2013 09:38 AM
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daveparry1

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If the screws go directly into wood there is no need to fit the caps, I have the same situation in my house! (1966)

Dave.
 20 March 2013 09:43 AM
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ebanner

Posts: 48
Joined: 18 January 2003

Thanks Dave.

I have another problem. I am fitting a new light that is not double insulated and requires an earth. The only options I think I have is to double insulate the mains wire going into the light. There is metal casings around the light bulb holders. I suppose I could lacque them?
 20 March 2013 09:55 AM
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AJJewsbury

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There is metal casings around the light bulb holders. I suppose I could lacque them?

From a safety perspective, paint, varnish, lacquer etc isn't recognised as basic insulation (see reg 416.1), so it's a bit dubious relying on it for a second layer of insulation.

I'd suggest either providing it with an earth (a 4mm2 G/Y single run to somewhere appropriate would do), or swapping it for a proper double-insulated fitting - there are plenty about - even metal framed ones - try google.

- Andy.
 20 March 2013 10:27 AM
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Phased

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Coo 1964! I was 6, we had some great Summers back then!

Hoping for a good one this year.

Don't forget to put the warning stickers on or near the CU (lighting circuit without cpc no class1 fittings blah de blah).
 23 March 2013 02:44 PM
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ebanner

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The other option, which is not a good one, is to connect the earth terminal of light to the neutral wire. The neutral wire is around earth potential so should not be a shock hazzard. The fuse will blow if any part of the light becomes live. I know this does not sound very good but I am just thinking of ways around. I believe the neutral is connected to earth at the local step down transformer.
 23 March 2013 02:49 PM
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ebee

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Never Never Never Never (& Never) ever do that!

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 23 March 2013 03:12 PM
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daveparry1

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I can't believe Ebanner said that Ebee!!

Dave.
 23 March 2013 04:15 PM
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dbullard

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I wasn't sure I read that comment right .....I had to read it twice !!!!

D

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 23 March 2013 08:35 PM
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DR2366

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And the reg for that solution is?

How about rewire it and change the box for a metal KO one, someone has to do it at some point? The wooden box when broken out leaves a whole the right size so no extra chopping out.
 23 March 2013 11:32 PM
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geoffsd

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Originally posted by: DR2366
And the reg for that solution is?

543.4.1 (esp) NOTE

ESQC 8(4), Q&CR 2002
 24 March 2013 04:19 PM
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Testit

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Some of the guidance stipulates when inspecting that non earthed metal lamp fittings can have a judgement call if away from extraneously conductive parts.e.g not in arms reach of a radiator, on a 30ma RCD and that the lamp has good L/N to casing insulation test readings..... at your own risk if you actually install one new though....

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 24 March 2013 05:03 PM
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DALEC

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i ran a seperate earth to the fitting and put the lights on a rcd spur unit , thats about as safe as you can get without rewire .....

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 24 March 2013 05:04 PM
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DALEC

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i also filled the plate screwholes ith white silicon....

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 24 March 2013 08:49 PM
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daveparry1

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I'd say you've done as much as can be reasonably expected Dalec,

Dave.
 02 April 2013 04:51 PM
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ebanner

Posts: 48
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After all this I have persuaded er-in-doors to change to a double insulated fitting even if she was in love with that light!

My theory about neutral is it is connected to earth so why not connect it? I AM JUST THINKING OUT OF THE BOX HERE and not really going to do it but can anyone tell me?
 02 April 2013 05:22 PM
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AJJewsbury

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My theory about neutral is it is connected to earth so why not connect it? I AM JUST THINKING OUT OF THE BOX HERE and not really going to do it but can anyone tell me?

Because all it needs is a single break in the N somewhere upstream and the metalwork becomes live via connected loads.
- Andy.
 05 April 2013 04:50 PM
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Bluesmeister

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Originally posted by: ebanner

The other option, which is not a good one, is to connect the earth terminal of light to the neutral wire. The neutral wire is around earth potential so should not be a shock hazzard. The fuse will blow if any part of the light becomes live. I know this does not sound very good but I am just thinking of ways around. I believe the neutral is connected to earth at the local step down transformer.


My god man you are not only dangerous but bonkers.
 07 April 2013 01:20 AM
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jimmyoneball

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Originally posted by: DALEC

i ran a seperate earth to the fitting and put the lights on a rcd spur unit , thats about as safe as you can get without rewire .....


Is it just me? Whats the point of RCD protecting unearthed lights? RCDs only detect earth faults which will never be a problem on unearthed lights!
 07 April 2013 02:06 AM
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alancapon

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Originally posted by: jimmyoneball
Is it just me? Whats the point of RCD protecting unearthed lights? RCDs only detect earth faults which will never be a problem on unearthed lights!

Really? I suggest you do some research into how RCDs operate. You also need to think about what sort of fault a person coming into contact with a faulty light would give.

Regards,

Alan.
IET » Wiring and the regulations » Lighting circuit without an earth

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