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Topic Title: Light Fitting Earthing
Topic Summary: Fitting GU10 lamp-holders to replace existing MR16 installation. What are the earthing requirements
Created On: 19 November 2012 03:21 PM
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 19 November 2012 03:21 PM
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lawrenceshort

Posts: 6
Joined: 03 January 2003

I have a large number of MR16 halogen light fittings. Each of these has a transformer in the above-ceiling space, therefore the fitting is supplied with low voltage and is isolated from the mains by the transformer thus requiring no earthing.

I am planning to replace these lamps with GU10, LED types, powered directly from the mains. The GU10 lamp holders fit into the existing ceiling fittings currently housing MR16 lamp holders.

The question is, do the ceiling fittings now need earthing as the lamp holder now has mains fed directly to it. The ceiling fittings have no provision for an earth wire attachment? Are the GU10 lamp holders double insulated, possibly negating the need for earthing the fitting?

To avoid any doubt, the transformers will of course, have been removed.

Manufacturers web-based literature does not appear to address this issue.
 19 November 2012 03:33 PM
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AJJewsbury

Posts: 10964
Joined: 13 August 2003

The question is, do the ceiling fittings now need earthing as the lamp holder now has mains fed directly to it.

According to BS 7671, yes (presuming the lamp holders aren't suspended from a ceiling rose or similar). 411.3.1.1 - A Circuit protective conductor shall be run to and terminated at each point in wiring and each accessory except an lampholder having no exposed-conductive-parts and suspended from such a point.
- Andy.
 19 November 2012 08:19 PM
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lawrenceshort

Posts: 6
Joined: 03 January 2003

Andy - I should have explained that they are flush mounted ceiling fittings as used in bathrooms and of metal construction. Because the fittings originally held MR16 (low voltage and mains isolated) lamps, the fittings have no provision for connecting an earth wire. The new GU10 lamp holders have live and neutral wires only - no earth.
 19 November 2012 08:24 PM
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hifly

Posts: 649
Joined: 06 November 2005

but there should be an cpc (earth wire) at the transformer.

however as your fitting has no cpc connection i suspect they are class 2 so won't require a cpc to be connected, check the instructions as the info you need should be in there.

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Vince

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 20 November 2012 01:12 PM
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AJJewsbury

Posts: 10964
Joined: 13 August 2003

Andy - I should have explained that they are flush mounted ceiling fittings as used in bathrooms and of metal construction. Because the fittings originally held MR16 (low voltage and mains isolated) lamps, the fittings have no provision for connecting an earth wire. The new GU10 lamp holders have live and neutral wires only - no earth.

Even if the fittings are class 2 (double insulated) you still need to run an c.p.c. to them - I gather it's in case they're replaced by class 1 fittings in future (generally accepted as a DIY-able) - a suitable c.p.c. must be available.
- Andy.
 20 November 2012 05:06 PM
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lawrenceshort

Posts: 6
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Thanks again Andy. I think the only safe thing to do is to run a cpc to the ceiling housings or to buy complete new GU10 ceiling fittings and replace the existing MR16 ones. The lighting feed to the existing MR16 transformers does have a cpc available.
Lawrence
 20 November 2012 08:35 PM
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hifly

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sorry i miss-read your original post and thought you were fitting a whole new fitting not using your existing fittings.

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 21 November 2012 08:01 PM
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koicarpus

Posts: 35
Joined: 14 June 2010

Hi
I fit a certain type of fire rated downlight which are gu10 and don't need an earth, i,e, class 2.
The gu10 lamp holder does seem to be chunkier than normal, maybe this is why the downlight itself doesn't need earthing.
I personally can't see a problem with what you are imposing.
Regards
Dave
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