Earthing wall lights
 

I have replaced the wall lights in an upstairs room in my house. The
new wall lights need to be earthed. Fortunately the supply is via a
twin and earth cable where the earth was shortened and taped up.

I have enough leeway to use the earth in the supply cable, so my
question related to where to earth these lights to.

In the loft I have water tanks with copper pipe down as far as the
ground floor stop cock where the pipes go out of sight.

Should I get an earth strap and earth these lights to the incoming
water supply pipe, or do the regulations / best practice say I should
do something else.

Many thanks

Phil

In message , Aardvark
writes

I have replaced the wall lights in an upstairs room in my house. The
new wall lights need to be earthed. Fortunately the supply is via a
twin and earth cable where the earth was shortened and taped up.

I have enough leeway to use the earth in the supply cable, so my
question related to where to earth these lights to.

In the loft I have water tanks with copper pipe down as far as the
ground floor stop cock where the pipes go out of sight.

Should I get an earth strap and earth these lights to the incoming
water supply pipe,

No.

or do the regulations / best practice say I should
do something else.

You use the earth in the cable - that it what it is for.

Just connect them up to the earth in the cable. I am assuming here that
the earth in the lighting circuit is all connected up properly back to
the consumer unit.
--
Chris French, Leeds

On Sun, 17 Oct 2004 20:41:48 +0100, Aardvark
wrote:

Should I get an earth strap and earth these lights to the incoming
water supply pipe, or do the regulations / best practice say I should
do something else.

Best way is to find the most convenient socket which has an earth to
it and bond it there.

Relying on water pipes is not ideal because however unlikely it may
seem a plumber (or whoever) could disconnect the pipe and thus break
the bond.

Using the incoming water mains as the bonding (earthing) point went
out a while back. Bonding arrangements using pipework is used for
something called equipotential bonding - to keep all the pipework at
the same potential (voltage if you will), and that might not
necessarily be ground.

The ideal situation would be to run the earth back to the consumer
unit. If you do run an earth wire any distance it's best to make it a
fair size (4mm or better).

Andrew

On Sun, 17 Oct 2004 22:03:15 +0100, chris French
wrote:

In message , Aardvark
writes

I have replaced the wall lights in an upstairs room in my house. The
new wall lights need to be earthed. Fortunately the supply is via a
twin and earth cable where the earth was shortened and taped up.

I have enough leeway to use the earth in the supply cable, so my
question related to where to earth these lights to.

In the loft I have water tanks with copper pipe down as far as the
ground floor stop cock where the pipes go out of sight.

Should I get an earth strap and earth these lights to the incoming
water supply pipe,

No.

or do the regulations / best practice say I should
do something else.

You use the earth in the cable - that it what it is for.

Just connect them up to the earth in the cable. I am assuming here that
the earth in the lighting circuit is all connected up properly back to
the consumer unit.

When I bought my house some 20 years ago I noticed that two (metallic)
wall lights in the living(!) room were wired with 2-core flex buried
diagonally in the wall directly from the back of a pair of 13A sockets
as a spur from a 30A ring main...

Needless to say these lamps have long gone!
Frank Erskine
OETKBC

In message , Frank Erskine
writes

When I bought my house some 20 years ago I noticed that two (metallic)
wall lights in the living(!) room were wired with 2-core flex buried
diagonally in the wall directly from the back of a pair of 13A sockets
as a spur from a 30A ring main...

Needless to say these lamps have long gone!
Frank Erskine
OETKBC

Creepy!!!!!!!
I had exactly the same 10 years ago. The 9KW shower was also wired with
2.5mm T&E via a 13A fused spur. Only noticed the shower wiring after a
couple of weeks when the 13A fuse blew. There was such a volts drop in
the cable that the fuse mustn't have been too much over its rating, nice
warm wall though!
--
Bill

In article , "Andrew McKay"
says...
On Sun, 17 Oct 2004 20:41:48 +0100, Aardvark
wrote:

Should I get an earth strap and earth these lights to the incoming
water supply pipe, or do the regulations / best practice say I should
do something else.

Best way is to find the most convenient socket which has an earth to
it and bond it there.

Until someone decides to rip out that socket.

Thanks for the replies. I have some follow-up questions.

One poster said to tie my earthing requirements back into the main
earthing system.

The cabling we are talking about here is all in the loft of the house
and I do not recall seeing any earthing cabling up in the loft at all.
The lighting circuits do not have any earth wires and there are no
power sockets in the loft. Only a single lighting circuit.

Should I look further for an earting system up there. This is a
1930's house with a wiring system from that era, although most cables
are of the newer (white PVC) type I suspect the wiring layout design
is of the 1930 era.

In message , Philip
writes
Thanks for the replies. I have some follow-up questions.

One poster said to tie my earthing requirements back into the main
earthing system.

The cabling we are talking about here is all in the loft of the house
and I do not recall seeing any earthing cabling up in the loft at all.

Well you wouldn't normally see any separate earth conductors.

The lighting circuits do not have any earth wires and there are no
power sockets in the loft. Only a single lighting circuit.

So you mean the cable that supplies the wall light points has an earth
conductor, but the circuit that it connects to presumably predates this
and does not have one?

In that case you need to add one back to the consumer unit. I don't know
if connecting to the earth on another circuit is allowable, but I
certainly wouldn't want to do it. While you could add a separate earth
cable back to it as suggested, I would look into rewiring the lighting
circuit with T&E (you could do this in bits as you decorate)

Should I look further for an earting system up there.

I would certainly want to check over the whole system

This is a
1930's house with a wiring system from that era, although most cables
are of the newer (white PVC) type I suspect the wiring layout design
is of the 1930 era.

We have a '30's semi, partly rewired in the 1960's. If our experience is
anything to go by you will end up rewiring the lot eventually anyway.
Lighting circuits won't have an earth, there won't be enough sockets -
don't assume a sensible ring main, ours was a total hotpotch of a a ring
but most of the sockets were pond various spurs all over the place.

I would want to check that there is no of the original probably 1930's
rubber cable - if so you want to get rid of it ASAP (look carefully,
some of our switches had PVC cable that connected to the original rubber
cables buried in the wall behind the switch)
--
Chris French, Leeds

In article ,
Philip wrote:
The lighting circuits do not have any earth wires and there are no
power sockets in the loft. Only a single lighting circuit.

That makes the lighting wiring rather old - although if PVC could still be
ok.

Should I look further for an earting system up there. This is a
1930's house with a wiring system from that era, although most cables
are of the newer (white PVC) type I suspect the wiring layout design
is of the 1930 era.

Don't think very much has changed in design, really.

If the wiring is as easy to get at as you suggest, I'd be tempted to
replace the lot with TW&E. Bodging an earth on here and there just as
absolutely necessary isn't good practice.

--
*If you can read this, thank a teecher

Dave Plowman London SW
To e-mail, change noise into sound.

" The lighting circuits do not have any earth wires"

If this is the case then you really need to be replacing the circuit with
modern cable.

You can then earth the wall lights through this

Will


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chris French wrote:

In that case you need to add one [CPC] back to the consumer unit. I
don't know if connecting to the earth on another circuit is
allowable, but I certainly wouldn't want to do it.

Unless the circuit is RCD protected (unlikely), Reg. 544-01-01 will
apply and dictates that the CPC (circuit earth) must be "incorporated in
the same wiring system as the live conductors or in their immediate
proximity."

So "no" is the probable answer, but a 'borrowed' earth (as a temporary
measure) is better than no earth.

I would want to check that there is no of the original probably 1930's
rubber cable - if so you want to get rid of it ASAP (look carefully,
some of our switches had PVC cable that connected to the original rubber
cables buried in the wall behind the switch)

Yours too! 1930s usually means cotton-covered VIR in conduit. Given
the OP's obvious lack of knowledge here an inspection and probably a
complete re-wire by a competent person would seem to be indicated.

--
Andy