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

 

[ezzzekiel]

using the adiabatic will result in a smaller size and the main bonding would need to be not less than half, if using 54.7 then pretty much 16mm required but as youre on tncs then the bonding conductor is sized to the neutral at 10mm which brings up another argument from work.

10mm earth on tncs with 6mm bonds and told to leave as is because the adiabatic will meet the earth requirements but the bonding wouldnt because of table 54.7 - cant win..

 

[Guest123]

I cant wait until theres a problem with the gas meter.......

 

[telectrix]

I cant wait until theres a problem with the gas meter.......

bit of a ballache to fiddle that gas meter

 

[Stormflex]

Tell me about it. Not so long ago they wanted to upgrade the electricity meter. I opened the cupboard and invited him to go ahead. He very quickly changed his mind and reported it as inaccessible.

 

[telectrix]

Tell me about it. Not so long ago they wanted to upgrade the electricity meter. I opened the cupboard and invited him to go ahead. He very quickly changed his mind and reported it as inaccessible.

what a wimp!

 

[Dave_]

You use the adiabatic or table 54.7

reg 543.1.1

table 54.7 is very broad and errs on the side of safety

so if it complies using the adiabatic then i dont see why it needs changing....

 

[cbw]

That looks like a 16mm anyhow???????????

Going to fetch my glasses

 

[cbw]

Yep even with my glasses on that looks similar in size to the 16mm tails.....Looks like 2*10mm and a 16mm.....BONUS!!!

 

[Stormflex]

You reckon? Would indeed be a bonus if that were the case.

The earth cable hanging down in front of the tails is going to the water pipes. The earth on the left in the MET is the earth up to the CCU. All three earths in the MET appear to be the same size. Hence my assumption that they are all 10mm.