Understanding minimum CPC requirements?

[Octopus]

Most of have 10mm and 16 mm to hand .... 10 mm nearly every time for me

 

[telectrix]

as a dedicated scouser, the min size should be 50mm, bare copper preferred.anything less just aint worth taking to the weigh-in.

 

[Gavin John Hyde]

I see you are with Stroma @happyhippydad I havent had this conversation with the local NICEIC assessor, but when ever I question what the assessors or other such folk say, I say can you show me where that is in the books so I can read up on it later. They quickly move on! Similar things happens with building control poking there noses in when doing visits.

 

[Deleted member 26818]

Yes, minimu CSA is 2.5mm2 if provided with mechanical protection. In other words, a sheathed single.

 

[Deleted account]

I said I'd be back with reg no

Yet again a contradiction.

On site guide table 4.4(iii) states the 4mm

Under neath in notes the contradiction :
The main protective bonding conductors shall have a cross sectional area not less than half that required for the earthing conductor and not less than 6mm.

So the main protection bonding conductors have to be min6mm and its ok for earthing conductor to be 4mm or even 2.5mm.
Shirley the earthing conductor should have the path of least resistance.

Have I interpreted that correctly?
I hope not.

 

[D Skelton]

Yes Pete, you have.

The earthing conductor and bonding conductor serve completely different purposes.

The former is there to carry current and is sized accordingly, the latter is there to equalise potential and is sized accordingly.

It's perfectly reasonable to expect that on many TT installations the bonding conductor/s will be larger than the main earthing conductor.

 

[Deleted member 26818]

Yes that is correct.
The CSA of the earthing conductor with both TN-S and TT can be less than that of the bonding conductors.

 

[Octopus]

Yes that is correct.
The CSA of the earthing conductor with both TN-S and TT can be less than that of the bonding conductors.

Yup - shame the muppets who are assessing people don't seem to understand this

I blame the pretty pictures in the front of the OSG

 

[Deleted member 26818]

Yup - shame the muppets who are assessing people don't seem to understand this

I blame the pretty pictures in the front of the OSG

There was one edition of the OSG which said the minimum CSA for the earth in TN-C-S was 6mm2.
I think line and neutral were listed as 25mm2, so it could have been a mis-print for 16?

 

[Deleted account]

I have got to admit I didn't know this. Though with the explanations given I totally understand why.

I don't know why I didn't know it.

Anyone else out there didn't know it also? Go on admit it.

Or is it just me and the assessors?

Thanks

 

[Deleted account]

Just me then.