Main bonding

[Deleted member 9648]

Evening all,
Have kind of over thought this one until I'm not sure any more! Input welcome.
Have been installing a supply to a machine, and gathering the necessaries for the EIC today I noted that the bonding is undersized. It's a 400a incomer with 185mm tails into an MCCB panel DB. TNCS....and main bonding to water,gas and steel is in 25mm. Table 54.8 gives a minimum CSA of 50mm where the supply neutral is over 150mm. Where I've started to doubt my initial assessment is that I've taken the tails as the benchmark for the supply neutral size....or should it be the DNO incomer neutral CSA which I cannot confirm? Been a long day and I'm not thinking straight.
It matters because it is an installation newly constructed 5 years ago, and a recent EICR by another contractor didn't flag any issues with bonding. Don't want to look a dick and flag up a non-issue.

 

[davesparks]

In the UK, I believe ESQR requires all distributed TN-C-S supplies to be PME.

Can you be a bit more specific about what you mean by distributed?
A single point TNCS supply will be PNB, which this could quite possibly be at 400A

 

[happysteve]

This is an interesting discussion. I'm learning stuff. I'm grateful when those with knowledge spread it around a little.

 

[ruston]

This is an interesting discussion. I'm learning stuff. I'm grateful when those with knowledge spread it around a little.

Just for you then.

http://www.cablejoints.co.uk/upload/Earthing___Guidance_Notes__Central_Networks.pdf

Go to the bottom first for PNB.

 

[happysteve]

Just for you then.

http://www.cablejoints.co.uk/upload/Earthing___Guidance_Notes__Central_Networks.pdf

Go to the bottom first for PNB.

Cheers Ruston

 

[ruston]

You are welcome. I hope you find it useful.