10mm earthing conductor

[Stormflex]

Changed CCU in my house and am completing the paperwork.

It appears that the earthing conductor is only 10mm. The main protective bonding conductors are also 10mm.

Am I obliged to upgrade this (will be no easy task!) or can I put this in the comments section on Form 1 and in the Deviations from Wiring Regulations box on the schedule of test results?

 

[telectrix]

what earthing system?

 

[Stormflex]

Sorry, TN-C-S

 

[telectrix]

10mm for main bonding is fine. what's the problem getting a 16mm from the CU to the MET.? that's all you need.

 

[Guest123]

I would point you to reg 131.8 in BS 7671.

You could then use the adiabatic equation to check wether the existing 10mm is sufficient, precluding a TN-C-S earthing system of course where is must be sized in accordance with the supply neutral conductor.

 

[i=p/u]

ruke of thumb is same up to 16mm but could be less if you do your sums

 

[telectrix]

i can't see the problem unless the CU is remote from the head

 

[i=p/u]

amp x amp x disconection time squared rooted / installation method numbers,

 

[telectrix]

amp x amp x disconection time squared rooted / installation method numbers,

ands that makesas much sense as tea squared minus biscuit

 

[i=p/u]

your too old to understand new tricks,

 

[Stormflex]

ok - looks like i'll have to go and buy some 16mm earth cable then.

telectrix - it'll just be a pig to route. CCU is in the top of a kitchen cupboard, MET is below worktop height right in the back corner of a cupboard on the wall at 90deg to CCU wall. They've basically wired it all up and then built the kitchen infront/around it. Just trying to get the end of the cable into the MET will be a challenge:



But, I am sure I will overcome

 

[pennywise]

ok - looks like i'll have to go and buy some 16mm earth cable then.

telectrix - it'll just be a pig to route. CCU is in the top of a kitchen cupboard, MET is below worktop height right in the back corner of a cupboard on the wall at 90deg to CCU wall. They've basically wired it all up and then built the kitchen infront/around it. Just trying to get the end of the cable into the MET will be a challenge:

View attachment 3510

But, I am sure I will overcome

You'll do that easy looks like a pain but once you get cracking it'll be a breeze.

 

[Stormflex]

I've got to climb in here first



And I'm not what you'd call petite

 

[telectrix]

if the 10mm main earth is behind cupboards, maybe you can use it as a drag to pull the 16mm thru. good bit of practice for you here, sort of thing we have to do a lot of, or try a fish tape or rod alongside the tails. remember, for every problem there is another one round the corner.

 

[telectrix]

I've got to climb in here first

View attachment 3511

And I'm not what you'd call petite

that's why we have skinny apprentices