Main Bonding issues. Help!

[dellboy78]

I want to try and keep this short so i'll do my best! I was recently doing some work for an electrical and building firm who were fitting new kitchens to council flats. We were basically altering kitchen circuits and/or installing new ones if needed and issuing the relevant certificates. We were told that if we found the main bonding or earthing was not adequate that we were not to rectify it, but report it to another firm who have the maintenance contract for them to deal with. I have done this and held back the certs for these jobs. The maintenance firm are now disputing the presence/adequacy of the main bonding and before I take it further I wanted to guage opinion here to make sure that I am in the right. I wont go into all the details just yet but a lot of the issues are with the bonding being done in communual areas but not locally to the flat. I am of the opininon that it should be done in each flat as well as communal areas. Other times a 10mm bond has been taken from the flats consumer unit but the consumer unit is only supplied with a 6mm earth via its submain. On some occaisons where I have not seen any evidence of bonding they are saying they have done a long lead test to prove the bonding is in place but I think they are testing between the m.e.t. and the actual pipework without actually seeing a bonding cable! Surely any number of parallel paths could be giving false readings here?
Opinions please! I can give more info if needed. Thanks guys!

 

[malcolmsanford]

Personally I'm for once in the agreement with the NICEIC on this one, each flat should have it's own bonding Earth Marshaling Point (EMP) and therefore be bonded back to either that point an earth block or the CU main Earth Bar.

If you happen to have or get hold of a copy of the NICEIC Earthing Snags and solutions it gives you clear and precise illustrations on it.

As for the bonding conductor size that will be relaint on the earthing system involved. For TNC-S it would be to the neutral on the DNO incoming cable and bear no resemblance to the sub main CPC size.

For TN-S and TT it is in relation to the size of the main earthing conductor in the installation, in this case the sub main CPC, and so 6mm would be adequate

 

[Engineer54]

Totally agree with Malc, Each apartment should be considered as a separate installation, and therefore have it's own bonding arrangements connected to that apartments EMT be it a separate connector block or the earth bar of the apartments CU... Bonding on PME/TNC-S should be a min of 10mm. Sub main min CPC size can be determined by adiabatic calculation, though length of run on high rise apartments needs to be taken into consideration, depending on how the power distribution has been installed. (ie, rising main systems) ...

 

[Guest123]

If you happen to have or get hold of a copy of the NICEIC Earthing Snags and solutions it gives you clear and precise illustrations on it.

It's in GN8 too, I think thats where they get their dagram from.

 

[dellboy78]

Thanks for your replies. Is there actually a regulation that says each flat should have its own main bonding or is it just a recommendation? These people want the absolute minimum done and at the moment are saying that as it is done communally that it is sufficient?

 

[sedgy34]

It Seems what you were told originally is down to money and by doing what they wanted you to do may have left you wide open.
based on regs YOU should be telling them whats required not other way round.

 

[PC Electrics]

Snags and Solutions - a Practical Guide to Everyday Electrical Problems: Earthing and Bonding Pt. 1: Updated to IEE Wiring Regulations 17th Edition, BS 7671: 2008 Niceic: Amazon.co.uk: Electrical Safety Council, National Inspection Council for Electr

See if you can borrow a copy from someone or else try your library?

You're quite correct as others have said, but if you want to persue the matter you really need to get hold of the relevant books (incl GN8) and reference these. You'll get nowhaere simply offering your (or our) "opinion".

 

[PC Electrics]

It Seems what you were told originally is down to money and by doing what they wanted you to do may have left you wide open.
based on regs YOU should be telling them whats required not other way round.

I'd have to agree with Sedgy here. YOU have carried out work which requires earthing and/or bonding to be upgraded. YOU are responsible for making those upgrades as part of the work. OR YOU must have a watertight contract that states this work will be carried out by others. AND, as I see it, YOU are the competent person and so YOU should be stipulating those flats where remedials are required. On what basis (other than money) are this "maintenance crew" disputing YOUR requirements? What competency level do they hold?

 

[Guest123]

411.3.1.2 states "In each installation, main protective bonding bonding conductors must connect all the extraneous conductive parts to the main earthing terminal (MET).

The above reg would apply to each flat which has it's own supply & metering equipment, under the definition of an electrical installation as defined in part 2 of BS 7671.

Therefore, main protective bonding conductors should be selected in accordance with section 544, if none are present, they do not comply with this section.


Essentially, main incoming services should be bonded at the point of entry to the actual building & the point of entry to each seperate flat in accordance with the above regulations.

 

[sedgy34]

you could end up doing the additional works free of charge to cover your arse being the competent person you RODNEY

oh sorry your dellboy arnt you!!!! :smilielol5:

 

[dellboy78]

Thanks again. I do have the snags and solutions book and have held off getting GN8 until the updated version comes out next month. I am willing to stand by my opinions but just wanted to make sure there aren't any 'loopholes' that the other firm could trip me up on. Apparently one of their blokes works part time for the NIC so would have thought he would know his stuff.
What are your thoughts on long lead tests from the pipework to the met? I cannot see how they can use this to say the bonding is sufficient, and if they have had to use this method, even if there was some hidden bonding connection then am I not right in saying it has to be visible/accessible?
Cheers

 

[sedgy34]

Thanks again. I do have the snags and solutions book and have held off getting GN8 until the updated version comes out next month. I am willing to stand by my opinions but just wanted to make sure there aren't any 'loopholes' that the other firm could trip me up on. Apparently one of their blokes works part time for the NIC so would have thought he would know his stuff.
What are your thoughts on long lead tests from the pipework to the met? I cannot see how they can use this to say the bonding is sufficient, and if they have had to use this method, even if there was some hidden bonding connection then am I not right in saying it has to be visible/accessible?

firstly NIC are not always correct as ive proved in the past!!Yes the bonding is supposed to be accesible for inspection as your doing kitchen refurbs, i assume the bonding will be readily accesible for inspection when that maintanance company send that part time NIC bloke to have a look.
i think if they want to they can make this very difficult for you, are you niceic?

 

[dellboy78]

I'm not nic sedgy, so even if i sign these certs the QS for the firm I was doing the work for will have to sign them as well. I just want to do the right thing and not be made to look like a t*t about it. As you say, they have been to look at these jobs and now it has been put back on me to comment and i'm sure they could make it difficult for me if they wanted to. I am however under pressure to hand over the certs I have held back.

 

[sedgy34]

I'm not nic sedgy, so even if i sign these certs the QS for the firm I was doing the work for will have to sign them as well. I just want to do the right thing and not be made to look like a t*t about it. As you say, they have been to look at these jobs and now it has been put back on me to comment and i'm sure they could make it difficult for me if they wanted to. I am however under pressure to hand over the certs I have held back.

the best thing to do is say they sort the earths as agreed and you will inspect before handing over the certs

 

[LukeBuckaz]

Surely when carrying out a long wonder lead method of testing they should be disconnecting at least one end of the bond to eliminate parallel paths. The reading should 0.05ohms or less. If I remember rightly this equates to about 27 metres of 10mm.