6mm Earth and Main protective bonding conductors

[westward10]

This may be off interest to you?

The Electrical Safety First best practice guide no 1. Changing a Consumer Unit.

States that 6mm main earth and bonding conductors don't need to be changed when "they have been in place for a significant time and show no sign of thermal damage".

A pdf version is downloadable from their website.

End of discussion, we have it it black and white from the idiots guide to electrical work.

 

[Ian1981]

An idiots guide put together by members of the iet, niceic, napit, beama, city and guilds,EAL, select,BSI
Yep all idiots with no electrical knowledge or background

 

[Andy78]

End of discussion, we have it it black and white from the idiots guide to electrical work.

The particular idiots guide you mention is endorsed by the same organisations involved with writing the regulations that you said you would blindly follow regardless of new or existing installation.
Is the regs an idiots guide of higher calibre ?

 

[buzzlightyear]

http://electrical.------.org/wiring-matters/16/earthing-questions.cfm?type=pdf
may be this will help.

 

[Octopus]

The BYB and OSG are there to confuse the masses

 

[westward10]

An idiots guide put together by members of the iet, niceic, napit, beama, city and guilds,EAL, select,BSI
Yep all idiots with no electrical knowledge or background

It is not relevant who put it together as it obviously not done by idiots, my views on it don't change.

 

[Ian1981]

It is not relevant who put it together as it obviously not done by idiots, my views on it don't change.

That's cool.
I meant no offence

 

[westward10]

That's cool.
I meant no offence

No offence taken Ian

 

[Gavin John Hyde]

Given BS7671 is not a statutory document or law but guidance can't we use our 'competent' knowledge and skill to make a informed decision to list all the departures and do as we see appropriate in the circumstances... after all there was a case recently where some office of officialdom took a case to court where a cowboy spark had been doing notifiable work and it went a bit wrong... the judge refused to allow the big yellow book to be used in the case as he said it has no legal basis its not a statutory document that must be complied with.

 

[westward10]

What did the judge allow.

 

[Gavin John Hyde]

@westward10 sorry case was actually a few years back now not so recent, but principle applies it seems..... British Standards/IEE Regulations and the Judicial System - Letter to the Editor - https://www.voltimum.co.uk/articles/british-standardsiee-regulations-and

 

[Michaelwgroves]

This may be off interest to you?

The Electrical Safety First best practice guide no 1. Changing a Consumer Unit.

States that 6mm main earth and bonding conductors don't need to be changed when "they have been in place for a significant time and show no sign of thermal damage".

A pdf version is downloadable from their website.

Good find, so it says;
A 6mm or 10mm earthing conductor used with an associated line conductor of 25mm could be considered adequate if the requirements of regulation 543.1.3 are met.

This is the good old adiabatic equation. I've tried to do this before but get stuck, anyone know how to do this?

 

[Ian1981]

Good find, so it says;
A 6mm or 10mm earthing conductor used with an associated line conductor of 25mm could be considered adequate if the requirements of regulation 543.1.3 are met.

This is the good old adiabatic equation. I've tried to do this before but get stuck, anyone know how to do this?

I've given you the formula from my first post or have you just ignored it?

 

[Michaelwgroves]

These are my figures (I think);
S=6 (6mm earth cable)
k=143 (70 degree thermoplastic)
t=0.03 (30ms)
I2=1.08 (Prospective fault current)

As a starting pint does this look correct?

 

[Ian1981]

These are my figures (I think);
S=6 (6mm earth cable)
k=143 (70 degree thermoplastic)
t=0.03 (30ms)
I2=1.08 (Prospective fault current)

As a starting pint does this look correct?

S is what you are trying to find.
It's not the 6mm already in place.
First find the fault current which by measuring ze , can be calculated.
So a ze of 0.10 gives a fault current of 2300 amps
I2 so 2300 x2300=
Then multiply by the disconnection times given for the OCPD in the cut out using appendix 3 tables.
If below 0.1 seconds the let through energy figure is to be used given by the manufacturer.
Square root the answer and divide by say 143 if the earthing conductor is a separate cable and not bunched with the live and neutral 'tails'
This will give you S which is your required CSA of the earthing conductor for compliance

In this example scenario ,Using a disconnect time of 0-1 seconds and a fault current of 2.3ka will give a CSA of 5mm rounded off so 6mm is adequate