Advice on regulation 521.5.1

[davesparks]

dave,
I never mentioned bonding conductor, only referencing a cpc as an "earth" using the term "earth" as it had been used in an earlier post.
A bonding conductor is not part of the circuit that the SWA is supplying.

How exactly does one inform that bonding conductor that it is not to be a cpc? Regardless of what it gets called it will still be a part of the earth loop and carry it's share of the fault current.

 

[andyb]

They don't allow it to enter through a different point, never have.

'Read and understand the regulation number quoted in the OP and all will become clear.'

Your words.

 

[netblindpaul]

Yes, as I said, read and UNDERSTAND the reg.
Where it is REQUIRED.
If it is not REQUIRED then it is NOT ALLOWED.
So, if you can generate a scenario where it is REQUIRED, then it is ALLOWED.
However, I doubt you can actually prove a reason to install a separate cpc.
Look it up do the calcs, and then come back and show where a seperate cpc is REQUIRED, considering that the SWA must act as an adequate CPC for the circuit anyway else it is not acceptable.

 

[netblindpaul]

'Read and understand the regulation number quoted in the OP and all will become clear.'

Your words.

Yep my words, so go back, read and UNDERSTAND the regulation.

 

[netblindpaul]

How exactly does one inform that bonding conductor that it is not to be a cpc? Regardless of what it gets called it will still be a part of the earth loop and carry it's share of the fault current.

It's a bonding conductor, NOT a circuit CPC.
They are different items, they, can be combined, however a cpc is a cpc, and it must act as a cpc.
If you want it to be a bond as well then that is something different.

Remember BS7671 only considers a single fault.

 

[spadge47]

i'll reword the question.

does a main earthing conductor have to go through the same holes as the main tails in a metal wylex board?

the tails come straight out the meter into a metal board through a wylex gland..

and if so then why does the tt wylex gland only have 2 holes and not 3.

 

[netblindpaul]

i'll reword the question.

does a main earthing conductor have to go through the same holes as the main tails in a metal wylex board?

Yes.
Though what Wylex has to do with it I don't know.
Also remember there is no requirement to fit metal boards until 01/01/16.
Until them flammable and dangerous boards are quite acceptable regardless of what is said on the internet.

 

[Deleted member 26818]

All conductors of a circuit should enter a ferrous metallic enclosure through the same hole.
I don't know why there has been a relaxation of this requirement in recent years, it may be because it has become industry standard?

 

[spadge47]

Unfortunately, my employers have decided to do away with plastic boards last month, can only fit metal.

 

[davesparks]

It's a bonding conductor, NOT a circuit CPC.
They are different items, they, can be combined, however a cpc is a cpc, and it must act as a cpc.
If you want it to be a bond as well then that is something different.

Remember BS7671 only considers a single fault.

How does the conductor know that it is a bond and not a cpc? the armour as cpc and the seperate bond are effectively connected together at each end, so any flow of current is going to split between them proportionally.

 

[andyb]

Yep my words, so go back, read and UNDERSTAND the regulation.

Paragraph 3

These requirements do not preclude the use of an additional protective conductor in parallel with the steel wire armouring of a cable where such is required to comply with the the requirements of the appropriate regulation in chapters 41 and 54.It is permited for such an additional protective conductor to enter the ferrous enclosure individually.

 

[davesparks]

Yes, as I said, read and UNDERSTAND the reg.
Where it is REQUIRED.
If it is not REQUIRED then it is NOT ALLOWED.
So, if you can generate a scenario where it is REQUIRED, then it is ALLOWED.
However, I doubt you can actually prove a reason to install a separate cpc.
Look it up do the calcs, and then come back and show where a seperate cpc is REQUIRED, considering that the SWA must act as an adequate CPC for the circuit anyway else it is not acceptable.

I have already mentioned the situation where a seperate protective conductor is required, that of needing a main bond. The regulation states protective conductor not circuit protective conductor. Bonds are protective conductors.

 

[netblindpaul]

Paragraph 3

These requirements do not preclude the use of an additional protective conductor in parallel with the steel wire armouring of a cable where such is required to comply with the the requirements of the appropriate regulation in chapters 41 and 54.It is permited for such an additional protective conductor to enter the ferrous enclosure individually.

Like I said, read and understand, REQUIRED is the relevant word.
If REQUIRED, it's OK, when is it REQUIRED?
If it's not REQUIRED, then it's NOT OK, just like I said.

 

[netblindpaul]

How does the conductor know that it is a bond and not a cpc? the armour as cpc and the seperate bond are effectively connected together at each end, so any flow of current is going to split between them proportionally.

In which case as the fault current WILL be split equally then it is a requirement that the armour WILL take the full fault current, thus the additional wire is not required.
The fault current will NOT split proportionally between the two conductors, at least not according to the research undertaken by the independent body that is the ERA.
Thus the SWA & the additional "cpc" must be capable of carrying the full fault current, thus, there is no need for the additional cpc.
QED.

 

[shanky887614]

states within the same enclosure not entry point so whats wrong.

L+N dont need to go through together if you slot it, or use paxolin/similar