School block Swa supply

[cliffed]

What code would you give for a Swa supply 3p/N,95mm.
Supplies remote school block,2 storey,no main earth conductor,using sheath,the main earth bonding originates from this Swa,for this block,@ Main Panel board,& is 16 mm
The main earth @ origin is 120mm,Main bonding 50mm.
Cheers

 

[Ian1981]

What code would you give for a Swa supply 3p/N,95mm.
Supplies remote school block,2 storey,no main earth conductor,using sheath,the main earth bonding originates from this Swa,for this block,@ Main Panel board,& is 16 mm
The main earth @ origin is 120mm,Main bonding 50mm.
Cheers

What do you mean no main earth conductor?
You’ve just stated earthing conductor is 120mm
Using the armour for a cpc is acceptable if sized correctly.
What is the earthing arrangement?
Using the armour as a combined cpc/bonding conductor could be acceptable if say it’s TNS

 

[cliffed]

Swa ,sheath used for main earth,the 120 mm Earth is at the origin intake of the school,this Swa is a sub main,to a remote block.
Tncs is the earthing system,185 mm Tails,120 mm Main Earth,50 mm earth bond.

 

[westward10]

Sheath is not the main earth, it is a cpc. I assume you are doing an EICR so you should know how to Code. What is your opinion.

 

[cliffed]

Correct a cpc,my opinion is a code 2.
A main earth should have been installed with this Swa,to provide an adequate earth,& Main earth bonding.

 

[Ian1981]

Correct a cpc,my opinion is a code 2.
A main earth should have been installed with this Swa,to provide an adequate earth,& Main earth bonding.

Your opinion is flawed unless inspection and testing revel otherwise.
Have you carried out the appropriate inspection and testing to verify that the current set up is potentially dangerous?

Again it’s a CPC not a MAIN earth

What is the earth arrangement?
Does the distribution circuit have adequate fault protection by ADS for its respective ocpd?

 

[westward10]

TN-C-S.

 

[cliffed]

Yea it’s a cpc the Swa is being used for Main Earth @ the Main Panel in the block.
It’s also being used for the Main earth bonding conductor.
The situation is not potentially dangerous,what are you going on about my opinion is flawed,
The earthing is Pme Tncs.

 

[cliffed]

TN-C-S.

Ha ha,someone’s got it

 

[Ian1981]

Yea it’s a cpc the Swa is being used for Main Earth @ the Main Panel in the block.
It’s also being used for the Main earth bonding conductor.
The situation is not potentially dangerous,what are you going on about my opinion is flawed,
The earthing is Pme Tncs.

I mean you can’t go on opinion, only by proof that it is potentially dangerous

 

[cliffed]

Ok,it’s been in place since early 70’s,so no it’s not potentially dangerous.
The nitty gritty here is,the sub main to the block.
My opinion is it’s not correctly installed.
The cpc would be ok in protecting the Swa,but not ok to support Main earth bonding.
Code 2

 

[Ian1981]

Ok,it’s been in place since early 70’s,so no it’s not potentially dangerous.
The nitty gritty here is,the sub main to the block.
My opinion is it’s not correctly installed.
The cpc would be ok in protecting the Swa,but not ok to support Main earth bonding.
Code 2

But if you believe it’s not potentially dangerous how can you then code 2 it?

 

[cliffed]

It’s also a Distribution circuit,thinking a main earth should be present,sized accordingly.

 

[cliffed]

But if you believe it’s not potentially dangerous how can you then code 2 it?

Reasoning cable not sized,to accommodate main earth bonding.
The other code then would be Either FI or 3

 

[westward10]

This is common in schools where new blocks have been put up.

 

[Darkwood]

I am guessing the OP is concerned more so about equipotential bonding in the block as this will need to meet the requirements of the size and nature of the supply and if my brain serves me correctly , you cannot utilise the SWA sheath to satisfy this, it would need to be a dedicated core or a seperate conductor.... this is all assuming that equipotential bonding is required in the block itself?

It doesn't help and only confuses matters when you get muddled up with your terminology of how you describe the layout - it is a sub-main therefore using the term 'main earth' is incorrect as that is your primary earth conductor at the origin.

 

[cliffed]

Agree,sorry about that,what code would you give it.
Main earth bonding would be necessary

 

[cliffed]

This is common in schools where new blocks have been put up.

What’s your coding on that

 

[Ian1981]

The PEN conductor and not the main tails would need to be 150mm or above for a requirement of a 50mm copper bonding conductor, so despite the fact it’s 50 mm in the main building could be down to an over specced original design and it maybe even larger than what is required.
It’s the PEN conductor which determines the required size of your bonding conductor however it’s most probably correct that your swa armour is going to be well undersized.
Sometimes you just have to assume it was designed correctly if you have no original design information, the existing building I mean and not the added block.

 

[Darkwood]

As above - you need to verify the requirements of the install and confirm them for us before we can comment, where required to be 50mm the equipotential bonding is there for safety reasons and is sized so to deal with network faults when associated with TNC based supplies, for example the N/E sheath of a PEN conductor suffers corrosion, this can lead to high resistance or even broken Neutral which can lead to high currents finding alternative paths through local installations.

EDIT- in answer, the SWA armour will probably be able to handle such a situation as it meets CSA compliance but falls short of regulations, this thus is not a safety issue but more so a compliance breach.