Adiabatic equation help

[spud1]

Hi guys,

I had a brain fog on the adiabatic.
Trying to ascertain suitability of a 6mm bonding conductor in a domestic installation. Doesn't help that I forgot my regs book too!

I have a pefc of 1.17KA. Can anyone help please?

Thanks.

 

[spud1]

Quiet this morning!
My thoughts were that if I could prove minimum size of the main installation earthing conductor and then use the 50% rule for the main bonding conductor it might come out at <6mm. Although I have just noticed that the installation has TNCS earthing! Does this mean I can't calculate and have to select from table??

Any help please?

 

[Ian1981]

It needs to comply with table 54.8, the adiabatic is not for sizing protective bonding conductors

 

[spud1]

Thanks Ian. Yes I know that's why that's why I was using the equation to size the installation earthing conductor and using the 50% rule to then size my bonding conductor. But in the absence of any books I couldn't remember whether I could that for a tncs installation?

 

[telectrix]

Thanks Ian. Yes I know that's why that's why I was using the equation to size the installation earthing conductor and using the 50% rule to then size my bonding conductor. But in the absence of any books I couldn't remember whether I could that for a tncs installation?

on a TNC-S installation min. size for bonding conductors is 10mm.

 

[spud1]

Thanks guys!! Really appreciate your help.

 

[Ian1981]

As said, 10mm is the minimum bonding conductor size, an existing 6mm tho doesn’t necessarily make an installation unsatisfactory.
Your earthing conductor would also need to be 10mm minimum if it’s a combination of protective bonding conductor and main earthing conductor.

 

[spud1]

As said, 10mm is the minimum bonding conductor size, an existing 6mm tho doesn’t necessarily make an installation unsatisfactory.
Your earthing conductor would also need to be 10mm minimum if it’s a combination of protective bonding conductor and main earthing conductor.

We're doing remedials at this installation, including a consumer unit upgrade. The route for rewiring the bonding conductor is unbelievably difficult! Is there any way I can risk assess to get around rewiring this 6mm bonding conductor? ?

 

[spud1]

Off on a bit of a tangent, but an niceic tech rep told me once on the phone about a calc that is in either the iet design guide or e&b guidance note (can't remember which) that can be done using either R2 or IR reading between a service pipe and the MET to prove whether is a genuine extrenuous conductive part which needs bonding.

Dont suppose anyone knows what I'm talking about do they?...

 

[DPG]

Off on a bit of a tangent, but an niceic tech rep told me once on the phone about a calc that is in either the iet design guide or e&b guidance note (can't remember which) that can be done using either R2 or IR reading between a service pipe and the MET to prove whether is a genuine extrenuous conductive part which needs bonding.

Dont suppose anyone knows what I'm talking about do they?...

I think you are talking about the test to prove whether an item is an extraneous part or not.

 

[spud1]

I think you are talking about the test to prove whether an item is an extraneous part or not.

Yes I am. Could you remind me what that test is please?

 

[telectrix]

IR test. pipe to MET. if >22kOhms does not need bonding.

 

[spud1]

IR test. pipe to MET. if >22kOhms does not need bonding.

Yes! That's it! Thanks Telectrix! ?

 

[cliffed]

main bonding protective conductors are sized by the Relevant table in the IEE REGS, not by adiabactic equation.

 

[telectrix]

main bonding protective conductors are sized by the Relevant table in the IEE REGS, not by adiabactic equation.

i just use whatever i find first on the van. still got a roll of plain green. (imperial). think it still has the price on the 100 yard drum.... £1.10.,6d.