High integrity earthing.

[GBDamo]

i understand the need, as I see it any circuit with a likelihood of more than 10 mA earth leakage should be subject to high integrity earthing.

This requirement can be achieved by many methods and I can see the sense in some.

Using RFCs instead of radials gives two paths so in the event of a break in the CPC it is still unlikely that the earth leakage will achieve mains potential. But why does it stipulate a 4mm CPC?

Is the use of 10mm simply a fudge so that distribution circuits can be classed as high integrity eathed?

Must admit to finding this confusing but interesting.

 

[Andy78]

Are you reading the OSG section on high integrity earthing ? If so the referenced regs should help.
10mm is the minimum conductor size for an independent protective conductor ..... unless it's made of copper, then it's 4mm.

I think that's right. I'm up to my cerebral cortex in certificates right now so please do check.

 

[Ian1981]

I think it’s to do with the robustness of the conductor.
It’s worth pointing out that the 4mm would need to be mechanically protected if used for high integrity earthing say in a radial circuit

 

[Nigel]

10mm is only required when there is no ring.

4mm is required when there is a ring.

2.5mm is required when there is a CPC and an earthed metallic conduit for example.

 

[Nigel]

I think it’s to do with the robustness of the conductor.
It’s worth pointing out that the 4mm would need to be mechanically protected if used for high integrity earthing say in a radial circuit

If it is a single protective conductor then it would need to be 10mm.

 

[Ian1981]

If it is a single protective conductor then it would need to be 10mm.

Not if used for high integrity earthing ran as a ring in a radial socket circuit.
4mm as long as mechanically protected is allowed

 

[Nigel]

Not if used for high integrity earthing ran as a ring in a radial socket circuit.
4mm as long as mechanically protected is allowed

Then it would not be a single protective conductor so yes.

 

[Ian1981]

Then it would not be a single protective conductor so yes.

A single copper protective conductor having a CSA of not less than 4mm complying with regulations 543.2 and 543.3.
The protective conductor being enclosed to provide additional protection against mechanical damage
If not mechanically protected then the minimum CSA is 10mm
543.7.1.203 indent (ii)

 

[Deleted member 26818]

Yes there’s does seem to some confusion.
10mm2 if not enclosed in a wiring system, 4mm2 if enclosed.
Minimum CSA is 1mm2.

 

[Ian1981]

I don’t know why there’s any confusion, it’s in black and white written in bs7671, gn8 ,gn1 and even the on site guide