Minor works and bonding

[liam b]

when you do a job which is say a spur off the ring in the living room but the customer wont have there earth bonding upgraded what do yous do?

cheers

 

[ezzzekiel]

Earthing and bonding are two seperate things, if carrying out a minor works there is no need to upgrade main bonding although a recomendation should be given

they were installed to a earlier edition of Bs7671 and were compliant then, however they should be proved to be adequate

 

[Sav]

Hi,
I always go the saying my old boss used to say.
" Earthing limits the duration of touch voltage...Bonding limits the magnitude of touch voltage"

regards,
Sav

 

[Johno]

Hi Liam, the way I have always understood it is that the addition has to comply with regs and if the main bonding is not there then the addition won't comply. So to sum up, I would insist on installing bonding. Though having said that, if the bonding was there but in 6mm2 I would just make a note on the minor cert.

 

[TPES]

To confirm...

Main bonding must be in place before any work is carried out, Minor Works or other..

If TN-CS then any electrical work must comply to BS7671 (17th ed) & requires the bonding to be 10mm (if the neutral conductor is less than 35mm, Table 54.8) So if 6mm, this needs upgrading what ever the type of work in any location...

If TN-S or TT then any electrical work must comply to BS7671 (17th ed) & requires the bonding to be not less than half the CSA of the earthing conductor and not less than 6mm. So if you had a 6mm or 10mm earthing conductor then a 6mm bonding conductor would be acceptable...

An example..

A customer would like new downlighters installed to the bathroom.
It is a TN-CS supply
bs3036 rewireable Fuse board
They have a 6mm main earth and 6mm bonding to gas and water services..

The solution to this would be to provide 30ma RCD protection to the addition/alteration or the whole circuit.
Upgrade the Bonding to 10mm....

If a TN-S or TT this situation would of only required RCD protection, earthing and bonding fine as is...

 

[Benny_Boy]

Earthing conductor and main bonding conductor(s) to current regs.

If not, tell the customer they must have them brought up to current regs before you do anything.

If customer refuses, walk away.

That's the official line.

that said, I think you can get away with undersized main bonding conductors provided they''re present and perform adequately.

 

[Markc]

I'm asking to confirm...

Main bonding must be in place before any work is carried out, Minor Works or other.. Correct?

If TN-CS then any electrical work must comply to BS7671 (17th ed) & requires the bonding to be 10mm (if the neutral conductor is less than 35mm, Table 54.8) So if 6mm, this needs upgrading what ever the type of work in any location...Correct?

If TN-S or TT then any electrical work must comply to BS7671 (17th ed) & requires the bonding to be not less than half the CSA of the earthing conductor and not less than 6mm. So if you had a 6mm or 10mm earthing conductor then a 6mm bonding conductor would be acceptable... Correct?

An example..

A customer would like new downlighters installed to the bathroom.
It is a TN-CS supply
bs3036 rewireable Fuse board
They have a 6mm main earth and 6mm bonding to gas and water services..

The solution to this would be to provide 30ma RCD protection to the addition/alteration or the whole circuit.
Upgrade the Bonding to 10mm....correct?

If a TN-S or TT this situation would of only required RCD protection, earthing and bonding fine as is.....Correct?

That is exactly how I understand it.

 

[Markc]

No matter what size of works if bonding and main earthing is lacking or insufficient then its got to be addressed. Reg's require it. NICEIC require it and so should you. Its up to you as the competent person to educate the client as to the importance of earthing and bonding. If they still refuse then I have to agree with a previous post you need to walk away. If you carry out the works it could possibly come back and bite you.

 

[Benny_Boy]

No matter what size of works if bonding and main earthing is lacking or insufficient then its got to be addressed. Reg's require it. NICEIC require it and so should you. Its up to you as the competent person to educate the client as to the importance of earthing and bonding. If they still refuse then I have to agree with a previous post you need to walk away. If you carry out the works it could possibly come back and bite you.

yep, gotta cover one's behind.

 

[TPES]

An apprentice has shown me this from esc.org website questions and answers

Can anyone else confirm 6mm is ok on PME, when you look at the regulation in the book it doesn't say anything at all about 6mm can stay, I've always upgraded to 10mm on PME, and this apprentice is telling me I don't need to...Look at this he says... (Contradicts its self to me)

Q2.12
When carrying out electrical work on an installation forming part of a TN-C-S system, is it necessary to upgrade existing 6 mm² protective equipotential bonding to 10 mm²?
Not necessarily. If the existing 6 mm² bonding connects all the extraneous-conductive-parts to the main earthing terminal, has been in place for a significant time and shows no signs of thermal damage, then it may not require to be upgraded.

Regulation number(s) 132.16 544.1.1

 

[sjm]

An apprentice has shown me this from esc.org website questions and answers

Can anyone else confirm 6mm is ok on PME, when you look at the regulation in the book it doesn't say anything at all about 6mm can stay, I've always upgraded to 10mm on PME, and this apprentice is telling me I don't need to...Look at this he says... (Contradicts its self to me)

Q2.12
When carrying out electrical work on an installation forming part of a TN-C-S system, is it necessary to upgrade existing 6 mm² protective equipotential bonding to 10 mm²?
Not necessarily. If the existing 6 mm² bonding connects all the extraneous-conductive-parts to the main earthing terminal, has been in place for a significant time and shows no signs of thermal damage, then it may not require to be upgraded.

Regulation number(s) 132.16 544.1.1

Your apprentice is correct, I've seen this on their website myself.
I can't see how it contradicts itself, 1st sentence is the question and the rest is the answer.

 

[TPES]

Ha ha, I get that, I mean contradicts its self with the regulation it states in the regs book (not esc) where does it state 6mm is fine on a PME

 

[sjm]

My reading of it is that earthing and bonding should be adequate for the alteration or addition according to 132.16.
544.1.1 does, as you say, state that where PME conditions exist the bonding conductor must be min 10mm. However I would say that this is intended for new installations.

Therefore if you consider that the existing 6mm conductor is adequate for the alteration/addition then it can be left in place and not upgraded.

I guess it depends on what the alteration/addition consists of.
It another situation where we're the experienced and qualified people so it's up to us to decide.

 

[TPES]

Any scenarios where you'd change to 10mm then on a PME? or are there none?

 

[sjm]

Any scenarios where you'd change to 10mm then on a PME? or are there none?

I'd upgrade if I were making major addition to the installation. New shower, new kitchen with extra sockets etc, that sort of thing.

 

[Engineer54]

Another What was a 4 year old thread!!

All to bring to our attention, one of the many contraditions to be found in BS 7671....

 

[TPES]

I agree, old thread, just wondered at what point different electricians would say a bonding should be upgraded on a PME, as some say there's no written rule its just down the the individual person, at what point would some of you say "right.. That bonding needs upgrading" or "leave that 6mm in it will be fine" and for what reason when the regs would require a minimum of 10mm.