543.7.1.203 - what does this reg mean in practical terms??

[rewireIT]

Can anyone shed some light on this in practical terms? Seems to say if earth leakage is over 10mA you need to run a 10mm cpc?

 

[Pretty Mouth]

I believe a ring final meets indent (iii).

 

[rewireIT]

I believe a ring final meets indent (iii).

So what about radials? Doesn't this basically say the cpc must be at least 4mm?

 

[nicebutdim]

Can anyone shed some light on this in practical terms? Seems to say if earth leakage is over 10mA you need to run a 10mm cpc?

It would only appear to state that if you were to give up reading a short way through the regulation.

Specifically this regulation deals with high integrity earthing - a subject inadvertantly raised in one of your recent threads.

I'm only a trainee, so couldn't begin to explain this regulation in great detail, but a post from @pc1966 in the aforementioned thread brings some relevance to this discussion.

Any tips on wiring 3x 2.5mm cpc's into a 13a socket?

Hi what do you mean by IT? Racking my brain here and can't think what you mean. Here "Information Technology" the idea being often that stuff has high leakage currents compared to common domestic loads. I think some of the rules might have been deleted with AM2

www.electriciansforums.net

 

[rewireIT]

It would only appear to state that if you were to give up reading a short way through the regulation.

Yeah you're right the regulation is clear as crystal, not sure how anyone could be at all confused by it.

 

[nicebutdim]

Yeah you're right the regulation is clear as crystal, not sure how anyone could be at all confused by it.

Regulation can very easily cause confusion - especially to those of us who haven't spent a great deal of time in this industry.

I quoted the post from @pc1966 as the link provides some helpful context. I would recommend reading it.

 

[davesparks]

Yeah you're right the regulation is clear as crystal, not sure how anyone could be at all confused by it.

Yes the regulation is very clear.

I think a lot of the confusion comes from people not reading it properly or reading what they think it says/what they think it should say rather than what it actually says.

The regulations are written in very specific, clear, technical English and unfortunately a lot of people just don't seem to understand this these days or want to take the time to learn.

 

[davesparks]

Can anyone shed some light on this in practical terms? Seems to say if earth leakage is over 10mA you need to run a 10mm cpc?

Running a 10mm CPC is one of the options for a circuit which is likely to supply equipment with a protective conductor current greater than 10mA.

There are 5 options for complying with this regulation and you need to comply with at least one of them but can use more than one at the same time.

Options i, ii, iii are going to generally be used for everyday/regular situations such as IT installations.
Options iv and v are more complex and so more likely to be used for specialist installations.


Option i is to have a CPC of at least 10mm, there is no mention of how it is to be installed or what material the conductor should be.
By not specifying the material or protection this creates a catch-all situation for pretty much every possible circuit that isn't a standard socket circuit.
This option is best suited to submains or final circuits feeding larger equipment and not well suited to standard socket circuits.

Option ii is to have a single copper protective conductor of at least 4mm which is mechanically protected.
This option is well suited to final circuits supplying sockets or for your average server rack etc.

Option iii is to have two protective conductors, each of which complies with section 543.
Having 2 CPCs effectively gives you a backup should the first become disconnected, if each one complies with section 543 then it is suitable to be the CPC of the circuit in such a situation.
Cable armour or conduit may be used as the second CPC (as long as it fully complies as a CPC for the circuit if it was being used as the only CPC for the circuit)

Further to this for option iii if both CPCs are in the same cable then the combined CSA of all conductors (L, N and CPC) in the cable must not be less than 10mm. This does not mean you need a 10mm conductor.
Whilst the purpose of this requirement may not be immediately obvious I think it is designed to ensure that the cable used is physically big enough to be more resistant to mechanical damage and less likely to suffer from incidental damage.