Earthing a back box

Spoon · Nov 17, 2015

Hi people.
I was talking to one of the guys at work about taking a wire from the earth on the socket to the metal back box. I know this has been discussed before but I can't find it in a search or in the regs. (must be having an off day).
I remember reading in a thread that as long as the back box has a fixed lug then there is no need for a separate earth but most see it as 'good working practice' to add one.
Clarification is needed. Is a separate earth from the socket to the back box required?

Richard Burns · Nov 17, 2015

You have answered your own question.
Back boxes are defined as an exposed conductive part (not sure why!) and must be earthed, the fixed lugs of a back box are an earth connection and so an earth tail is not required, however it is good practice. If there is no fixed lug then a tail is required.

Farmelectrics · Nov 17, 2015

if it has an earth connection on the back box use it its there for a reason

Spoon · Nov 17, 2015

Richard Burns said:
You have answered your own question.
Back boxes are defined as an exposed conductive part (not sure why!) and must be earthed, the fixed lugs of a back box are an earth connection and so an earth tail is not required, however it is good practice. If there is no fixed lug then a tail is required.

Thanks Richard. I thought I'd read it somewhere. Is there something in the BYB or OSG that states this?

Risteard · Nov 17, 2015

Spoon said:
Thanks Richard. I thought I'd read it somewhere. Is there something in the BYB or OSG that states this?

BS7671 only refers to connecting exposed conductive parts to Earth - it doesn't go into detail about any specific products.

It is dealt with in more detail in the Guidance Notes, which does mention backboxes.

malcolmsanford · Nov 17, 2015

543.2.7

The only time you need as per the regulations to fit a fly lead to a back box if the trunking, conduit etc is used as the CPC, and only then.

There is no regulation saying that a back box flush in a wall needs to have a fly lead, if above does not apply. The same as a back box does not need a grommit, but both cases are deemed "best practice"

happysteve · Nov 17, 2015

It's in Guidance Note 8.

- 2 fixed lugs: earthing tail is not essential although for best practice is highly desirable.
- 2 adjustable lugs: earthing tail is essential.
- 1 fixed and 1 adjustable: always desirable to provide an earthing tail. Some accessories only have one earthing strap and eyelet, so essential (in this case) that the earthing eyelet is located at the fixed lug position. If not (in other words, if your accessory has only one earthing stap and eyelet, and it lines up with the adjustable lug), then earthing tail is required to be provided.

malcolmsanford · Nov 17, 2015

happysteve said:
It's in Guidance Note 8.

- 2 fixed lugs: earthing tail is not essential although for best practice is highly desirable.
- 2 adjustable lugs: earthing tail is essential.
- 1 fixed and 1 adjustable: always desirable to provide an earthing tail. Some accessories only have one earthing strap and eyelet, so essential (in this case) that the earthing eyelet is located at the fixed lug position. If not (in other words, if your accessory has only one earthing stap and eyelet, and it lines up with the adjustable lug), then earthing tail is required to be provided.

I haven't the GN 8 to hand, but every guidance note will have the relevant reg to hand next to the note steve, what is that reg number that states the 2 lugs mate

happysteve · Nov 17, 2015

That's the weird thing. It doesn't state a reg. It mentions 543.2.7 in the preceding text (which is about providing an earthing tail to the accessory from trunking/conduit where the cpc is provided by the containment). But on the subject of the lugs: nothing.

It starts that section by saying: "A metal back box of a surface-mounted accessory is an exposed-conductive-part [no argument there!], and a metal back box for a flush-mounted accessory is deemed to be an exposed-conductive-part. Back boxes, like all exposed-conductive-parts, are required to be earthed."

In my original post #7 I was pretty much quoting GN8. They are making the point that for 2 fixed lugs "the box can be considered adequately earthed through the earthing straps and eyelets of the accessory."

malcolmsanford · Nov 17, 2015

Thanks Steve, not trying to be a smart a*** but please do use the GN notes as they are written, guidance, and unless they quote a regulation then they are pure guidance.

I'm not saying that they are not good guidance but I get really annoyed sometimes with the IET about this. There argument is that anything in the GN notes that are regulations, will have the relevant reg to refer to. All the rest is guidance.

Use them like any tool mate, but it's the BYB that is what we should go to for the regulations

Risteard · Nov 17, 2015

malcolmsanford said:
Thanks Steve, not trying to be a smart a*** but please do use the GN notes as they are written, guidance, and unless they quote a regulation then they are pure guidance.

I'm not saying that they are not good guidance but I get really annoyed sometimes with the IET about this. There argument is that anything in the GN notes that are regulations, will have the relevant reg to refer to. All the rest is guidance.

Use them like any tool mate, but it's the BYB that is what we should go to for the regulations

Absolutely. I'm sick of seeing quotes from Guidance Notes / On-Site Guide quoted as "Regulations" or "Requirements" - they are an opinion and nothing else. Only BS7671 contains the Wiring Regulations.

happysteve · Nov 17, 2015

malcolmsanford said:
Thanks Steve, not trying to be a smart a*** but please do use the GN notes as they are written, guidance, and unless they quote a regulation then they are pure guidance.

I'm not saying that they are not good guidance but I get really annoyed sometimes with the IET about this. There argument is that anything in the GN notes that are regulations, will have the relevant reg to refer to. All the rest is guidance.

Use them like any tool mate, but it's the BYB that is what we should go to for the regulations

No argument from me, I'm with you all the way.

My original post was aimed at the thread original post, along the lines of, "I'm sure I've seen this somewhere..." well, that somewhere is GN8.

As someone just starting out, the guidance notes are an invaluable source of knowledge, in terms of interpreting the regs and stating what [the IET thinks] is best practice. If you can't cite a source for a statement, it's pretty low value.

They even teach you about this sort of thing on the level 2 course...:

[ElectriciansForums.net] Earthing a back box

It continues... "This will lead to the statutory enforcement system and criminal courts. For example, a breach in the non-statutory IET Wiring Regulations may have a significant effect on safety and ultimately result in a breach in statutory legislation.

Even if a breach in non-statutory regulations is not a legal issue, the consequences can be far-reaching. The industry may lose faith in the offending organisation's ability to perform, resulting in a loss of customers and tenders. In the case of the rules of trade and similar organisations, breaches may result in expulsion from the relevant organisation."

Quoting what someone said on an internet forum (unless they cite a suitable source) is off the bottom of the triangle

Risteard · Nov 17, 2015

Good post happysteve.

Mark Wright · Apr 26, 2020

happysteve said:
No argument from me, I'm with you all the way.

My original post was aimed at the thread original post, along the lines of, "I'm sure I've seen this somewhere..." well, that somewhere is GN8.

As someone just starting out, the guidance notes are an invaluable source of knowledge, in terms of interpreting the regs and stating what [the IET thinks] is best practice. If you can't cite a source for a statement, it's pretty low value.

They even teach you about this sort of thing on the level 2 course...:

View attachment 30703

It continues... "This will lead to the statutory enforcement system and criminal courts. For example, a breach in the non-statutory IET Wiring Regulations may have a significant effect on safety and ultimately result in a breach in statutory legislation.

Even if a breach in non-statutory regulations is not a legal issue, the consequences can be far-reaching. The industry may lose faith in the offending organisation's ability to perform, resulting in a loss of customers and tenders. In the case of the rules of trade and similar organisations, breaches may result in expulsion from the relevant organisation."

Quoting what someone said on an internet forum (unless they cite a suitable source) is off the bottom of the triangle

it seems questionable how the Regs could hold up in court with Regards to bonding and Earthing when so much of it is so unclear with Hundreds and Hundreds of Questions on bonding and earthing on the Net another hundreds and hundreds in the classroom, surprised someone hasn't considered taking action the other way round.

davesparks · Apr 26, 2020

Mark Wright said:
it seems questionable how the Regs could hold up in court with Regards to bonding and Earthing when so much of it so unclear with Hundreds and Hundreds of Questions on bonding and earthing on the Net.

The regulations aren't really very unclear, their language is usually pretty precise.

The biggest problem is people reading the regs who don't understand the correct/proper meaning of the words used, or who have a preconceived idea of what they think should be written there so they try to force what is written to fit their ideas.

Earthing a back box

Spoon

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Richard Burns

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Farmelectrics

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Spoon

-

Risteard

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malcolmsanford

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happysteve

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malcolmsanford

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happysteve

-

malcolmsanford

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Risteard

-

happysteve

-

Risteard

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Mark Wright

davesparks

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