New Light Fitting - Earth?

oneillk

I have a new light fitting with an earth cable. my existing lighting does not have an earth. I have 3 cables connected into the existing block and two of them inserted together.

What do i do with the earth on the new fitting?

thanks

10-10-20

The earth should have been brought down with the wiring - it was a mistake if it wasn't.
Pull the cables out from the ceiling as much as possible and have a look to see if the earth is bonded into the insulation of the live-wire from the wall-switch. It should physically be part of this.

Antenna

there would usually be no earth conductor on old lighting circuits.

oneillk

Its would be an old lighting circut. i.e.around 1980 houseing estate. Do i need to install and earth! if so, how do you do that?

cheers

Stoner

Back then only the lights downstairs needed to be earthed, or sparks got away with not earthing upstairs, it is very possible that you will need to get an earth from somewhere, either at the board or from somewhere else you could pick one up, back to the boards with a 2.5sq.mm earth would be best.

RoundyMooney

Stoner wrote: »

Back then only the lights downstairs needed to be earthed, or sparks got away with not earthing upstairs

I never knew that. There are quite a few houses built in the eighties with no earthing for lighting circuits whatsoever.

The good old pre RECI days...

fishdog

The good old pre RECI days...

I remember those days. I helped rewire many houses and larger buildings with my farther. We would then go to the ESB offices and pick up a completion cert (for free!).

The ESB then came out and inspected an installation and went through it with a fine toothed comb. You either complied or they would not connect! How times have changed!

RoundyMooney

Even when I was metering around the place, just prior to the trialling of isolators, ESB's involvement in installation inspections was dwindling.

As of '94, we were (just!) checking polarity in one or two random sockets, checking PSC, and earth loop impedance. Actually it's just as well that isolators came out when they did, as I can't imagine ESB completing the level of connections that they did during the housing boom, if they had to vet every one of them

I'm getting a little off topic here (mainly because the original query has been answered) but do any of you guys use "online" completion certs yet?

Hoagy

RoundyMooney wrote: »

I'm getting a little off topic here (mainly because the original query has been answered) but do any of you guys use "online" completion certs yet?

Oh yes, very satisfactory too.

fishdog

As of '94, we were (just!) checking polarity in one or two random sockets, checking PSC, and earth loop impedance.

I guess it depended on who you got and how much time they had. Anyway I was mainly talking about the eighties.

oneillk

So do i really need to get an earth installed?

Stoner

oneillk wrote: »

So do i really need to get an earth installed?

the best safe advice to give you is yes, it's up to you at the end of the day.

Mr Magnolia

You only need an earth on a light fitting if there are exposed metal/conductive parts.

oneillk

http://www.diy.com/diy/jsp/bq/nav/nav.jsp?action=detail&fh_secondid=9197460&fh_start_index=12&fh_eds=%3f&fh_location=%2f%2fcatalog01%2fen_GB%2fcategories%3c%7b10099%7d%2fcategories%3c%7b8960079%7d%2fcategories%3c%7b8960080%7d%2fspecificationsProductType%3dCeiling+Lights%2fstyleStyle%3e%7bcontemporary%7d&fh_refview=lister&ts=1197977976394&isSearch=false

This is the fitting.

Its a lot of work to put in an earth!!! How do you get the cables accross the ceiling/rooms and into the board with out wrecking the place.?

Mr Magnolia

That fitting should really have an earth. I've seen them installed without though.

You can take an earth from a number of places, you don't have to go back to the board. Is there an attic above the ceiling?

Stoner

looks stainless steel or some sort of conductive material, so yes it would require an earth.

However with a risk of being hammered here, you could always try to get an earth from your hotpress (if the hotpress has an earth going to it) then you could connect onto the eatth strap that has a cable going back to the board. It's not ideal but its better than nothing


edit, dont do this I got the hammering i predicted

Mr Magnolia

I wouldn't go that route Stoner. Could the hot-press pipework not then become the fault-path?

oneillk

The light is centered in the sitting room on ground floor which corresponds to the ceneter of bedroom floor (carpet and floorboards) above. The board (old fuse type, not the trip) is only about 3.5m away but there are two blovk walls between, one of which runs the full height to the attic.

Mr Magnolia

If it was me I would put the light up without an earth then.

Note that this is what I would do, I'm not advising you from a professional perspective. You could always get an electrician in for a look or a quote?

You should also consider getting your consumer unit replaced, any good electrician will advise you of this anyway.

Stoner

Mr Magnolia wrote: »

I wouldn't go that route Stoner. Could the hot-press pipework not then become the fault-path?

I agree with Mr Magnolia, I'd get a new board (and earth rod) you may need to get a sparks to visit to check out your wiring as you may have bigger issues then one unearthed light.

fishdog

Well as you know there should be a 4, 6 or 10sq earth from the hotpress connected to the pipes at the earth strap, this goes directly to the earth bar on the consumer unit , this is connected to the earth rod.

This is for equi-potential bonding (Spelling?) keeping the voltage between the pipes and between the pipes and earth at zero. Should an earth fault current flow down these cables the copper pipes with now have a potential difference across them with respect to earth (not advisable). If the light fitting developed a fault the fault current should go directly to the earth bar not through bonding of pipe work. I would be nervous of this.

Stoner

ok I'll edit my post, but just to make the point again, I was not talking about earthing to the pipes, I never said that, if you read the post I said to connect to the earth strap in the hotpress as this goes back to the main earth bar directly and everything is connected at the earth bar anyway, so if the path of least resistance is throught the pipework it will be taken by all fault currents as the pipework has a connection to the main earth and if this was the case a lot of the fault current would flow from the main earth bar through to the pipes as they are all connected anyway.

Mr Magnolia

I knew what you meant stoner and in theory it would have been fine. It's just if there was a problem with the earth anywhere in the loop-to-ground the pipe-work may become the path of least resistance, which was my main point. Even if you didn't bond to it directly as you explained. Nothing like constructive friendly debate

fishdog

I was not talking about earthing to the pipes, I never said that

I know that. I did not suggest that you ment that.

just if there was a problem with the earth anywhere in the loop-to-ground the pipe-work may become the path of least resistance

Well put. I have often seen plumbers making alterations removing "those useless f***ing cables"

Or one pipe may become a higher potential than something else that is earthed.

The earth cables in the hotpress is connected to the earth bar, but it is not there to carry fault currents, it is there to keep conductive pipes etc. at the same potential relitive to each other and earth. The earth in the light fitting is there to carry a fault current to earth without that current flowing through the bonding, that is why they are kept seperate.

Sparky

If you really have to use that fitting, try and get an earth to it even from say a socket on the landing/bedroom etc. All earths are common. Although I dont like robbing earths for lights from socket circuits, it still is a safe path back to earth.

Otherwise you could go on a search for a double insulated light fitting that doesnt need an earth by looking for this symbol and save some headwreaking.

I have 3 cables connected into the existing block and two of them inserted together

Probably giving the time of the house, 1 red and 2 blacks, the 2 blacks are together as these are loop neutrals.
If you happen to be changing this fitting remember to pull the fuse or knock down the breaker.