After some advise please- Tn-s earth arrangement

[Deleted member 9648]

The purpose of the 'continuous guidance' is to prevent loss of bonding downstream where a single conductor loops from one service to another should it be partially disconnected. There is guidance somewhere, I cant remember where, and that guidance also states that a durable maintenance free joint is acceptable, such as a non insulated crimp ferrule. But none of the above is a requirement of Bs7671

 

[oracle]

Show us the regulation that stipulates earthing and bonding conductors have to be one continuous cable segment.

SC I did say clearly its Not in the Regs but stated in the GN8.

By way of an example... consider an SWA supply from the meter to a consumer unit some way away. There are various joins in that connection, this is acceptable. I find it hard to believe a correctly made join (say a crimp or a service terminal block) would not comply.

A soldered connection or single MET are deemed acceptable

So its not a reg then.

End of.

We all know the Regs are not statutory, but they are the only code of practice we have. Guidance notes are supportive, like the Parts 1 to 7 of the Building Regulations

If you've got access to the NIC's technical manual, it's in part B37-21, section 7.

 

[Octopus]

We all know the Regs are not statutory, but they are the only code of practice we have. Guidance notes are supportive, like the Parts 1 to 7 of the Building Regulations

If you've got access to the NIC's technical manual, it's in part B37-21, section 7.

But you are stating them as if they are 100% regulations which they are not ........... so please stop.

Do a survey on how many sparks have the BBB or BYB plus all the guidance notes ................. I suspect it won't be many...........

As for the NIC manuals - no I don't and as they don't write the regs, its not relevant ......... they could be promoted as NICEIC "best practice" but the NICEIC still couldn't pick members up on assessments for things like this................... they can't be arsxd to follow up on poor practice of their members either ........... yet dare to use their logo and not be a member - you'll be up in court ..... misplaced priorities IMHO

 

[westward10]

You don't mind perusing the Best Practice Guides though do you?

 

[Upton Sparks]

What Conductor did you think you were following?

If that is the main earthing conductor, then you have a problem and would need to call out the national Grids local sub contractor to your area ( possibly UKPN)to look at fixing a new earthing point to the SWA of the Sub main cable. They will charge for this service.
If they cannot do this, you would need to look at changing the earthing system to a TT system or having the supply cable replaced with a TN-C-S

I would Inform the customer of the bad news, its not something which can be ignored even if you're getting a good Ze reading

 

[Jimmer84]

That looks suspiciously like a copper pipe... gas or water maybe, so my guess from afar would be that's bonding not the main earth.

Yea it’s the gas pipe, the meter is to the right of the photo

 

[Jimmer84]

That’s not pretty.

What’s the Ze like?

0.18

 

[Jimmer84]

What Conductor did you think you were following?

If that is the main earthing conductor, then you have a problem and would need to call out the national Grids local sub contractor to your area ( possibly UKPN)to look at fixing a new earthing point to the SWA of the Sub main cable. They will charge for this service.
If they cannot do this, you would need to look at changing the earthing system to a TT system or having the supply cable replaced with a TN-C-S

I would Inform the customer of the bad news, its not something which can be ignored even if you're getting a good Ze reading

It’s the ONLY “earth” cable going to the cu. There was no earth clamp at the top of the supply cable so I thought maybe for some reason the connection was under the floor board as that is where the “main earth” was coming from to then enter the cu. Upon lifting the board that is what I found! Pulled on the bare cables and they didn’t budge, all head off slightly different angles!!

 

[Jimmer84]

 

[Jimmer84]

Thought people might like to see the nest of tails accompanying the dodgy earthing system too

 

[Deleted member 26818]

Guidance notes are written by the EIT to help you interpret the Regs correctly and the fact that people do a Regs course, usually at a college that simply prepares you to pass, doesn't mean that you are not responsible for studying it further.

How would you have managed 2391,2,4,5 or 6 without GN 3? Do you ever read it or quote it here, or just use the OSG like any domestic install, r?

Just because people can't be asked to study doesn't mean they can substitute opinion for fact.

No the GNs are not written by the EIT, or even the IET.
They are written by members, sometimes with input from other members, and are the opinion or interpretation of that member.
Yes, I have supplied input in the past for a GN3 (think it was the last time it was re-written).
I rarely read any of the GNs, and only read the OSG when looking for specific examples of errors.

According to your interpretation, connecting bonding conductors to an earth bar in a CU, then running a main earth to the main earth terminal in a PME cut-out would not comply.

 

[oracle]

No the GNs are not written by the EIT, or even the IET.
They are written by members, sometimes with input from other members, and are the opinion or interpretation of that member.
Yes, I have supplied input in the past for a GN3 (think it was the last time it was re-written).
I rarely read any of the GNs, and only read the OSG when looking for specific examples of errors.

According to your interpretation, connecting bonding conductors to an earth bar in a CU, then running a main earth to the main earth terminal in a PME cut-out would not comply.

OK, point of order. All the books published by the IET, including BS7671, are written by the contributions from the members.

That said, the IET seal of approval is on these guidance books.

My understanding of main protective bonding is that it must be >=10mm, resistance not >0.05 Ohms, that it is run from the MET or Earthing bar in a CCU to extraneous and/or exposed conductive parts.

Where there is a connection between the MET and earthing bar it is normally provided from the MET to the Earthing bar it is usually to minimise the number of 10 mm conductors into the CCU.

The Earthing conductor is from the Earth electrode or conductor to the MET. This can be seen in Fig 2.1.

In your example, these are interconnections not joins in the length of the conductor so comply.

 

[oracle]

You don't mind perusing the Best Practice Guides though do you?

Not at all, I value the guidance that the best practice guides and other reputable books give. The declaration in the model forms uses "to the best of my knowledge and belief".

The reason I contribute to the debates is that my knowledge may be lacking in certain things and wrong in certain beliefs and I would rather be proven wrong here than in court.

 

[oracle]

What do you think ?

 

[telectrix]

My understanding of main protective bonding is that it must be >=10mm, resistance not >0.05 Ohms,

that is wrong.the 0.05ohm relates to the resistance between a bonding cable and the pipe to which it is attached.nothing to do with the resistance of the cable itself.

 

[oracle]

By way of an example... consider an SWA supply from the meter to a consumer unit some way away. There are various joins in that connection, this is acceptable. I find it hard to believe a correctly made join (say a crimp or a service terminal block) would not comply.

Have a look at Fig 2.1 .The local earthing arrangements may include interconnections between components like Meters, CCU's and MET's, but should not be joined in their length.

 

[oracle]

My understanding of main protective bonding is that it must be >=10mm, resistance not >0.05 Ohms,

that is wrong.the 0.05ohm relates to the resistance between a bonding cable and the pipe to which it is attached.nothing to do with the resistance of the cable itself.

The Regs don't give a maximum length of the main protective bond. One way in which the maximum length can be determined is to use the figure of 0.05Ω given in IET GN 3, 2.6.5. This gives the maximum resistance of a main protective bonding conductor measured from end-to-end when carrying out test method R2 on the bond.

 

[westward10]

Not at all, I value the guidance that the best practice guides and other reputable books give. The declaration in the model forms uses "to the best of my knowledge and belief".

The reason I contribute to the debates is that my knowledge may be lacking in certain things and wrong in certain beliefs and I would rather be proven wrong here than in court.

I wasn't aiming that at you. It was for someone who disregards the Guidance Notes in this yet happily makes reference to the Best Practice Guides in another thread.

 

[Octopus]

I wasn't aiming that at you. It was for someone who disregards the Guidance Notes in this yet happily makes reference to the Best Practice Guides in another thread.

Having a pop at me matey .................

The Best Practice Guides are simply that ............. in fact No 4 which I referred to is the only publication I'm aware of that gives some reasonably decent examples of the codes ...

Did I actually say I disregard the Guidance notes ......... no ............ I stated that they are not compulsory reading or owning and thus an NICEIC can't use them to give you a "black" mark on an assessment ..

 

[oracle]

If the Regs were statutory, written in English instead of Committee, we would be able to follow them properly without needing supportive documents.

Other countries, even in the so called 3rd World, get this right. Well, it's been interesting, but I think I'll go and have a nice lie down now.