earthing for tt system

[pactrol]

min size if buried unprotected

 

[IQ Electrical]

min size if buried unprotected

Are you asking a question?

 

[pactrol]

No was answering one

 

[IQ Electrical]

min size if buried unprotected

How is that an answer?

 

[holte end74]

What about supplementary bonding what size cable and do you have to do it in a TT ?

 

[SimpleSimon]

What about supplementary bonding what size cable and do you have to do it in a TT ?

Think you've gone a little off topic on this one mate! If he doesn't do TT he would than have to contact the DNO to provide an earth (if they can) and than he could be waiting weeks, even months. Besides if he sets up a decent TT system what's the need to change!!

 

[pactrol]

Beause this was your Question

Quote Why would you run a 16mm to a TT earth electrode?

 

[telectrix]

Beause this was your Question

Quote Why would you run a 16mm to a TT earth electrode?

the answer to that, pactrol , is you wouldn't as it's a waste of 16mm. when it's unecessary overkill

 

[NMc]

There is a lot of different point being raised here not sure if it is answering the question posed. We appear to be discussing the main earthing conductor, the protective bonding conductor, supplementary conductors and any other earthing conductor

The main bits from the regs

542.3 Earthing conductors
542.3.1 Every earthing conductor shall comply with Section 543 and, where PME conditions apply, shall meet the requirements of Regulation 544.1.1 for the cross-sectional area of a main protective bonding conductor. In addition, where buried in the ground the earhting conductor shall have a cross-sectional area not less than that stated in Table 54.1. For a tape or strip conductor, the thickness shall be such as to withstand mechanical damage and corrosion

Table 54.1 – Minimum CSA of a buried earthing conductor say
Protected against corrosion by a sheath & mechanical protection – 2.5mm² if copper
Protected against corrosion by a sheath BUT no mechanical protection – 16mm² if copper
NOT protected against corrosion by a sheath BUT mechanical protection – 25mm² if copper
NOT protected against corrosion by a sheath & no mechanical protection – 25mm² if copper

543 Protective conductors
543.1 Cross-sectional areas
543.1.1 The cross sectional area of every protective conductor, other than a protective bonding conductor, shall be:
i) Calculated in accordance with Regulation 543.1.3 [S=√I²t/k]
or
ii) Selected in accordance with Regulation 543.1.4

543.1.4 Where it is desired not to calculate the minimum cross-sectional area of a protective conductor in accordance with Regulation 543.1.3, the cross-sectional area may be determined in accordance with Table 54.7

​

Table 54.7 say
CSA of line conductor ≤ 16mm² protective conductor same size

CSA of line conductor ≤ 16mm² ≤ 35mm² protective conductor 16mm²
CSA of line conductor ≥ 35mm² protective conductor half the size of line conductor

Protective Bonding Conductors
544.1.1 Except where PME conditions apply, a main protective bonding conductor shall have a cross-sectional area not less than half the cross-sectional area required for earthing conductor of the installation and not less than 6mm². The cross-sectional area need not exceed 25mm² if the bonding conductor is of copper or a cross-sectional area affording equivalent conductance in other materials

544.2 Supplementary bonding conductors
544.2.3 A supplementary bonding conductor connecting two extraneous-conductive-parts shall have a cross-sectional area not less that 2.5mm if sheathed or otherwise provided with mechanical protection or 4mm if mechanical protection is not provided, except that where one of the extraneous-conductive-parts is connected to an exposed-conductive-part in compliance with Regulation 544.2.2, that regulation shall apply to the conductor connecting the two extraneous-conductive-parts

 

[pactrol]

Hi while it may well be overkill I was simply stating the Bs7671 wiring regs
Eg 542.3.1 Table 54.1