Earthing back boxes..

[mikeymoo]

A sparky told me today that you dont have to earth metal back boxes if they are RCD protected???? Right or wrong??

 

[adam.h]

I've always been taught to, so if there is an earth then yes I would.

 

[mikeymoo]

Thats what i told him. But he gave me the look of the devil
and snarled NO YOU DONT! lol i just walked away shaking my head.

 

[Spudnik]

You dont have to earth metal back boxes providing one of the plate fixing lugs is fixed.

Just be careful on singles as you have a choice of 2 adjustable, or 1 fixed and 1 adjustable.

Got nothing to do with RCD's.

 

[Bazspark]

A very useful piece of info i never heard before. In fact makes me wonder what else i dont know

 

[Spudnik]

Obviously if its a switch box, then all the earths get taken to the box and if a metal plate is used , a flylead to that.

 

[electro]

Its what your sparky mate doesn't know, that scares us...........

 

[mikeymoo]

If it scares you, how do you think i feel!

 

[Bazspark]

Did you know about the fixed lug Electro

 

[baldsparkies]

Its what your sparky mate doesn't know, that scares us...........

He is right in this instance though,
Its what my kitchen and bathroom fitter mates don't know that scares me.
And a lot more than another sparky.
I haven't come across a sparky that knows everything about our trade, and probably never will.

 

[Bazspark]

I Agree but i have certaintly come across a lot who think they know it all.

 

[electro]

Did you know about the fixed lug Electro

No I have never heard of that, sounds Good but possibly one of those things passed from sparky to sparky?, is it in the regs..?

 

[mikeymoo]

what if the insulations on the line conductor failed and the back box becomes live. The circuit protection device wouldnt trip? So i would say YES, earth the back box. I mean how long does it take..

 

[baldsparkies]

I Agree but i have certaintly come across a lot who think they know it all.

Yep, and those are the ones that truly give cause for concern. (Been in the trade since 1972 and still learning)

 

[Spudnik]

Come on fellas.

When the accessory is screwed back the earth connection to the box is provided through the fixing screw from the plate.

You will probably find the CSA of the screw is more then the 1.5 fly lead that would be connected.

 

[alexg]

What possible reason can there be not too?
Sounds like a "logical" interpretation of a regulation with regrd to unfixed equipment?

 

[baldsparkies]

Come on fellas.

When the accessory is screwed back the earth connection to the box is provided through the fixing screw from the plate.

You will probably find the CSA of the screw is more then the 1.5 fly lead that would be connected.

Nice, Jason, a practical common sense approach to the situation, your a thinking mans electrician.

 

[mikeymoo]

Ive seen rusty and painted plate screws stripped threads etc. I would rather just connect 4 inch of cable and be done with. I think leaving it off is relying to much on the person that removes it at some point to put it back properly.

 

[Spudnik]

Ive seen rusty and painted plate screws. I would rather just connect 4 inch of cable and be done with.

Indeed and there is no reason why not.

However, i bet if you tested that screw with the plate still on, it would still be continuous to earth.

I would be more concerned as to why the screw is rusty!!!!

 

[baldsparkies]

Don't think I will lose sleep on this one, every man to his own.

 

[mikeymoo]

I would be more concerned with someone getting hurt.

 

[stretchyboy]

Jason is perfectly correct, the important use of this knowledge is not so much when you are fitting your own jobs(as that is often personal choice) , but when you are testing someone elses work. It is really imprtant to know the regulations inside out in order to have all the answers to give to anyone who disputes the faults that you are picking up in an installation.

Good post all

 

[stevo09]

just taken a look on the NICEIC website and somebody asked the question ""

"Could you please tell me if it is neccasary to earth a metal back box if it has one fixed lug" The reply from the niceic was "Where an accessory has an earthing terminal incorporated, the protective conductor should be connected at the earthing terminal

Myself i would go with that.

 

[Mr Mark Sparks]

just taken a look on the NICEIC website and somebody asked the question ""

"Could you please tell me if it is neccasary to earth a metal back box if it has one fixed lug" The reply from the niceic was "Where an accessory has an earthing terminal incorporated, the protective conductor should be connected at the earthing terminal

Myself i would go with that.

the truth is there are a few instances where the nic take a safer stance than others
ie they say max ze on tt 100 ohms but the regs say 200

i fly lead but its my choice i agree that with a fixed lug there is no need, when doing r1r2 tests i often test to the screw and its fine (flylead or not)

when doing a p i r if there are no flyleads on fixed lug boxes i dont write it down

 

[stretchyboy]

Ditto Mark Sparks, I usually fly-lead but will not put it on a PIR if someone else hasn't unless there is two adjustable lugs.

I always think that it ought to be done as a sparky may have the socket front off and if the cable is damaged at the entry to the box, then it may touch and liven the box. In that instance if the box wasn't fly leaded it could become live as the earth would be connected to the socket and the socket seperated from the box at the crucial moment.
Having said that, we can only go by the regulations as they stand today and only use our knowledge, guidance and best judgement. We cant fail things for not looking 'nice' .................. unfortunately

 

[mikeymoo]

This is what makes this forum invaluable to me. Great posts and sound advice.. Cheers guys

 

[Spudnik]

.... may have the socket front off and if the cable is damaged at the entry to the box, then it may touch and liven the box. In that instance if the box wasn't fly leaded it could become live as the earth would be connected to the socket and the socket seperated from the box at the crucial moment.

Thats you on the naughty step then as you should not be working live.

Therefore if the socket front was removed and the above happened, then only you would be to blame if the inevitable happened.

Work safe guys

 

[stretchyboy]

Thats you on the naughty step then as you should not be working live.

Therefore if the socket front was removed and the above happened, then only you would be to blame if the inevitable happened.

Work safe guys

Very true, but if you were trying to get a Zs at a light switch ................

 

[Spudnik]

Very true, but if you were trying to get a Zs at a light switch ................

If thats the case then normally the CPC's are connected to the box as there is nowhere else for them to go, with a flylead to the metal accessory if fitted.

Even so, Zs should be taken at the fitting.




i LOVE splitting hairs

 

[stretchyboy]

Ok a "T" earth socket then, where you cant get your standard plug from your meter into it and you haven't got an adaptor

 

[Notsosmart]

Ok I'll throw my thought grenade into the night (& lend myself to being shot-down!)

How about the requirement now for taking each leg of the ring to twin Earth lugs on socket faces; should we earth to the back-box from each of those? or how about taking one leg back to the back-box & then flylead to the socket face.

INCOMING

 

[Gravid]

Ha Ha, the thought grenade, i like it. I always double one leg back to the back box, thats what i was trained to do, so its kind of auto pilot. If theres two lugs on the socket face i connect one to each of them, mainly because i was told that at least if one does come loose or snap the face is still earthed.

 

[YTSOxford]

I was told about not having to earth the back boxes when there is a fixed lug but still fly earth the box just incase.

Although I have had another spark give me a headache over what should be earthed first! I always go straight into the earth lug on the socket then fly to the box, but he does it the other way round. Whats preferred???? Still got the headache from it!

 

[Spudnik]

There is no specific regulation with regards to this subject, however it is good practice to go to the socket terminals first as this is where the CPC should go, to protect the appliance/end user.

Earthing of the box is purely supplementary.

 

[YTSOxford]

Okay thanks, good to know!

 

[Mr Mark Sparks]

i also would go outlet first
if going to the box first dont cut the cpc those terminals are ****

 

[Lou7]

No need to earth back of box if you have one fixed lug is correct according to Niceic engineer. what about the reg that says all socket earths in separate terminals if they are to be used for computers, even at the DB!!