Earth overkill

[conrad]

Recently started with a firm and have been put on new build apartments which is late into 2nd fix stage. I terminated an MK 12 way split rcd board today, the supply is a 3 core SWA 25 mm glanded at each end and banjos bolted and starpped. I was arguing with 2 sparks, one who has ran the job, as to why there was a seperate 10 mm earth ran to the board... No its not a bond. I said "is that not overlill as you already have one of the 25mm cores and the armour". They both said the main boss wasnt happy they had only put 10 mm in and wanted 16mm in??? They then went onto say its a new reg.... I didnt want to argue as only recently started so not wanting to step on toes etc... Surely theres no reg stating a sepereate conductor needs to be ran in as they have here?

 

[shanky887614]

Recently started with a firm and have been put on new build apartments which is late into 2nd fix stage. I terminated an MK 12 way split rcd board today, the supply is a 3 core SWA 25 mm glanded at each end and banjos bolted and starpped. I was arguing with 2 sparks, one who has ran the job, as to why there was a seperate 10 mm earth ran to the board... No its not a bond. I said "is that not overlill as you already have one of the 25mm cores and the armour". They both said the main boss wasnt happy they had only put 10 mm in and wanted 16mm in??? They then went onto say its a new reg.... I didnt want to argue as only recently started so not wanting to step on toes etc... Surely theres no reg stating a sepereate conductor needs to be ran in as they have here?

i would use the internal 25m core.

the 25mm core is way overkill for the bonding anyway

 

[Darkwood]

Depends what is on this board ...are any of the mcb's type C or D and high current rated where maintaining a low zs would be needed to comply?
Does the installation have a high ze?
Has the DNO requested extra earthing arrangements due to network layout?
Is this a TNCS set-up where equipotential bonding is been connected to the Sub-mains and requires a larger earth du to size of supply?

I would be careful arguing your case until you ask the reasons behind the extra earthing.

Edit - you say they said regulations call for it, in my experience, any electrician worth their salt should be able to point you to the regulation as appose to try bluff their way out of explaining if your arguing with 2 of them then tell them to provide back-up for their claims.

 

[davesparks]

Being new build apartments I assume its basically the same as blocks of flats with multiple apartments fed from a larger DNO supply? In these cases you would normally expect the bonding to be bigger than the standard 10mm.
But one 25mm core of the SWA will satisfy this requirement and could normally be expected to fulfill the role of a CPC.

This does have all the hallmarks of someone who doesn't know what they are talking about passing off their nonsense as fact, usually very loudly to anyone who happens to be in earshot.

 

[conrad]

Depends what is on this board ...are any of the mcb's type C or D and high current rated where maintaining a low zs would be needed to comply?
Does the installation have a high ze?
Has the DNO requested extra earthing arrangements due to network layout?
Is this a TNCS set-up where equipotential bonding is been connected to the Sub-mains and requires a larger earth du to size of supply?

I would be careful arguing your case until you ask the reasons behind the extra earthing.

Edit - you say they said regulations call for it, in my experience, any electrician worth their salt should be able to point you to the regulation as appose to try bluff their way out of explaining if your arguing with 2 of them then tell them to provide back-up for their claims.

Just new apartments with standard cicuits youd expect, 7 cicuits in this one all type b mcb. Not sure on system type, havnt looked at mains. Cant see there being any requirements for low zs or there being a high...

 

[conrad]

Your assumptions are correct... I wasnt sure if there may have been a new reg id missed stating a seperate cable to a core within swa etc must be ran in... Which makes no sense to me but like i say didnt want to argue about it ... I didnt install just terminated.

 

[Deleted member 26818]

The new Reg, now allows a separate earth to be run along side the SWA.

 

[shanky887614]

The new Reg, now allows a separate earth to be run along side the SWA.

then why didn't they use 2c swa?

 

[Deleted member 26818]

I'm saying that the new Reg now allows a separate earth, as opposed to requiring a separate earth.
Who knows why they used a 3 core SWA and ran a separate earth?
Perhaps they know?

 

[davesparks]

The new Reg, now allows a separate earth to be run along side the SWA.

Which reg is this?

 

[conrad]

I'm saying that the new Reg now allows a separate earth, as opposed to requiring a separate earth.
Who knows why they used a 3 core SWA and ran a separate earth?
Perhaps they know?

You dont need a reg to allow you to run a seperate earth as this would mean before the reg you couldnt?

 

[Guest77]

Recently started with a firm and have been put on new build apartments which is late into 2nd fix stage. I terminated an MK 12 way split rcd board today, the supply is a 3 core SWA 25 mm glanded at each end and banjos bolted and starpped. I was arguing with 2 sparks, one who has ran the job, as to why there was a seperate 10 mm earth ran to the board... No its not a bond. I said "is that not overlill as you already have one of the 25mm cores and the armour". They both said the main boss wasnt happy they had only put 10 mm in and wanted 16mm in??? They then went onto say its a new reg.... I didnt want to argue as only recently started so not wanting to step on toes etc... Surely theres no reg stating a sepereate conductor needs to be ran in as they have here?

Well whats the problem?

 

[Deleted member 26818]

You dont need a reg to allow you to run a seperate earth as this would mean before the reg you couldnt?

No, it means that before the new Reg, running a separate earth did not comply.

 

[Deleted member 26818]

Which reg is this?

The one requiring conductors of a circuit to all be run within the same ferrous magnetic enclosure.
Which now has an exception allowing a separate earth to be run along side an SWA cable in certain circumstances.

 

[Leesparkykent]

Edit...