16mm T&E sub-main question

[jimmer]

I have been asked to price for a db change in a flat above a veterinary centre that the nurses on call stay in. The supply to the whole building is a TN-S 2 phase. It has a 16mm main earth conductor, 25mm tails and 10mm's to services.
The flat above is supplied with a piece of 16mm T&E on a 60A switch fuse on a seperate credit meter to a wylex re-wirable board. Is the 6mm cpc in the 16mm T&E allowed if it is ok with the adiabatic equation? or does it have to be upgraded to 16mm for me to be allowed to fit the new db? As usual to route a new cpc is a pig of a job!
Any help much appreciated

 

[marksparky]

no i dont think it would sufficce the earth conductor should be at least half the size of the line conductors 16/2=8 so therefore i wouldnt av thought the 6mm cpc wud do but i will stand corrected as usual

 

[andyb]

no i dont think it would sufficce the earth conductor should be at least half the size of the line conductors 16/2=8 so therefore i wouldnt av thought the 6mm cpc wud do but i will stand corrected as usual

No Mark, you definately cannot use half the line conductor size for your earth size with 16mm cable.

You either use 16mm earth or do the adiabatic equation, so Jimmer could use the 6mm intergral if the calculation allows.

 

[marksparky]

i personally always use split concentric for sub mains, occasionally il use armoured, obviously u cnt use 8mm but i thought i read sum wer if it was bein used as a sub main the earthing conductor wud have to be greater than half that of the phase? not disagreein with u andy genuine intrested

 

[andyb]

Its the same size as the line conductor up to 16mm,
then it's 16mm up to I think 35mm ( I need to check this in the regs, it might be 50mm but I'm fairly certain it's 35mm)
Then 1/2 the size of the line conductor after that.

 

[lewlec]

hi

i would have though you need a minimum of 10mm for main bonding in the flat.

 

[superd25]

hi

i would have though you need a minimum of 10mm for main bonding in the flat.

Hi also
I agree 10mm earth is fine!

 

[Sintra]

The minimum csa of the main earthing conductor must be determined by the adibiatic equation or selected from Table 54.7 543.1.1.
If the adibiatic equation is used, the minimum csa of the main earthing conductor must be 6mm 544.1.1.

 

[Amp David]

544.1.1 is for main protective bonding conductors.

 

[andyb]

This is a sub main, reading the op I would assume the main bonding was at the intake.

 

[bugsy]

10mm cpc - you've obviousley brrn distracted by the uniforms

 

[Forde]

I think it's a minimum of 10mm as Bugsy has said above. Table 4.1 in the osg. So looks like your running that separate single core earth cable for the new cu or let some other sod do it.

 

[andyb]

I think it's a minimum of 10mm as Bugsy has said above. Table 4.1 in the osg. So looks like your running that separate single core earth cable for the new cu or let some other sod do it.

Table 4.1 of the osg is for when the csa is not calculated as per 543.1.3 of the regs.

 

[aaelectric]

this is a sub main and not the main earth which is 16mm so only has to comply with the fuse zs

 

[Engineer54]

Bit late with that little gem, over 3 years too late to exact!!