Yet another bonding question

[jibjob]

Have been asked to quote for a re-wire of a 3 bed property, fairly standard stuff really except that the ground floor is a solid concrete floor with copper pipework to 4 radiators, a gas hob & a further 2 gas pipes up throught the kitchen. I've IR tested pipework from the MET & it comes up 0.00 Mohms, continuity gives a reading of approx 14 ohms. Thus, all pipework is extraneous & requires main bonding as far as regs are concerned.
Bonding pipework to the hob is not a problem although it'll need to be made accessible for inspection somehow. However, I'm not really sure how I'm going to loop a 10mm cable between 4 radiators in 4 different rooms while keeping it aesthetically pleasing to the eye bearing in mind that all bonding connections need to be made accessible for inspection. The supply is currently TT but Western Power have had a look & confirmed PME is present (earth terminal present on side of service head but earthing currently provided by rod sunk into the ground within what is currently the garage but is being converted into a downstairs bedroom).
I mention this because I could keep it TT & use a smaller sized MBC which might make life a bit easier. Originally I was going to use the available PME. I've never had to deal with this issue before so it's a new one on me. Any thoughts?

 

[ash_s3]

Have a look in your regs book/OSG all will become clear, OSG even has pretty pictures to follow.

 

[telectrix]

bond the water and gas mains, then you will find taht most if not all copper is bonded anyway through the pipework itself.

 

[kingeri]

You would need to bond the gas and water anyway, regardless of any tests you've done. I suggest ensuring that main bonding is in place first, then conduct any testing you feel is necessary on the pipework. Why are you considering bonding radiators together?

 

[i=p/u]

Maybe arms length apart

 

[telectrix]

farmers arms, or the foresters arms? both good pubs a few miles from me.

 

[amo]

Confirm the main bond then test. You may not have to supplementary bond because of the internal pipe work.

 

[i=p/u]

Been there once, no accessories matching , your left overs for pints and taxi home??

 

[jibjob]

You would need to bond the gas and water anyway, regardless of any tests you've done. I suggest ensuring that main bonding is in place first, then conduct any testing you feel is necessary on the pipework. Why are you considering bonding radiators together?

I would only (main) bond them if they were found to be extraneous. I guess I'll need to test again when main bonding to water & gas is in place. Hopefully all re-emerging pipework will be under 0.05 ohms.

 

[kingeri]

Wait a minute there chief.....is there main bonding present in this property or not? You absolutely must have main bonding in place if the incomers are metal, it's not optional! It is one of the most important parts of the electrical safety provisions in the property. You don't 'main' bond other pipework in the house.....that is supplementary equipotential bonding, and it is this that can be omitted these days providing certain criteria are met.

Once main bonding is in place, you usually find that supplementary bonding in special locations isn't needed, as the pipework is continuous.

 

[44ALLAN]

I've IR tested pipework from the MET & it comes up 0.00 Mohms, continuity gives a reading of approx 14 ohms.
Thus, all pipework is extraneous & requires main bonding as far as regs are concerned.

Nahh..............main bond the incoming gas/water etc and that covers all your 'pipework' in the 'zone' mate

 

[jibjob]

Wait a minute there chief.....is there main bonding present in this property or not? You absolutely must have main bonding in place if the incomers are metal, it's not optional! It is one of the most important parts of the electrical safety provisions in the property. You don't 'main' bond other pipework in the house.....that is supplementary equipotential bonding, and it is this that can be omitted these days providing certain criteria are met.

Once main bonding is in place, you usually find that supplementary bonding in special locations isn't needed, as the pipework is continuous.

Not at present but there will be when I'm finished, property is currently empty.

 

[Engineer54]

Jesus wept, just get the Gas and Water services main bonded as per the regulations, ....then come back if you're still encountering any problems!!

Why would you even be considering leaving this installation as a TT system when a PME Earth is currently available from the DNO??

 

[diditrain]

I vaguely remember someone raising this issue the other week, where pipework was bonded, buried and then re-emerging at various locations. Can`t remember who it was but i think that his assessor had suggested additional bonding where it re-emerged.

 

[Deleted member 9648]

I vaguely remember someone raising this issue the other week, where pipework was bonded, buried and then re-emerging at various locations. Can`t remember who it was but i think that his assessor had suggested additional bonding where it re-emerged.

If the pipework is buried in concrete within the building it is unlikely to 're-gain' an earth potential IMO as it will be above the DPM.If you assume the pipework is becoming extraneous through being in dry concrete then the entire floor will be 'earthy' and there would be no point in bonding anything at all. The OP's test readings are almost certainly the result of parallel paths.I would main bond services at the point of entry as normal.

 

[Engineer54]

If the pipework is buried in concrete within the building it is unlikely to 're-gain' an earth potential IMO as it will be above the DPM.If you assume the pipework is becoming extraneous through being in dry concrete then the entire floor will be 'earthy' and there would be no point in bonding anything at all. The OP's test readings are almost certainly the result of parallel paths.I would main bond services at the point of entry as normal.

That would depend very much on how old the property/building is. Older buildings won't have a DPM course. Either way, the pipework will be undoubtedly be ''earthy'' and as you say won't normally require any additional bonding other than the main bonding at point of entry...