Leave 6mm Bonding on TT?

[cyberjunction]

Hi All

Can someone please clarify for me? I have installed a circuit on a TT system but the gas and water only have 6mm bonding. Does this mean I have to upgrade it or just note it on the cert and advise the customer?

Many thanks

 

[Sintra]

If your main earthing conductor is 10mm then 6mm is fine for the main protective bonding conductors and would not need to be noted.

If your main earthing conductor is >10mm then note it on the cert it will only need replaced if it shows evidence of thermal damage.

 

[andekoch]

I thought the main earth (ie to the rod) only needed to be 2.5mm (4mm if no mech protection) for TT so 6mm main bonding is ok.

 

[pushrod]

I thought the main earth (ie to the rod) only needed to be 2.5mm (4mm if no mech protection) for TT so 6mm main bonding is ok.

It is as Sintra said -The main protective bond on a TT must be a min of 6mm² and not less than half the size of the main earth. You are correct in saying that the min size of an above ground main earth is either 2.5mm² or 4mm² depending on mechanical protection, but if someone has unnecessarily installed a 16mm² that would take the MPB up to 10mm² - in which case you would do a risk assessment checking for overheating of the MPB and note on the cert if you wanted to stay it as 6mm²

 

[cyberjunction]

thanks everyone main bonding is 16mm so technically is should be so 10mm then as I thought as half the size, the meter is outside - will have to upgrade i guess to be safe after i do a a risk assessment of course - thanks again all

ps not sure why they used 16mm as its only 2 meters from the meter!

 

[telectrix]

or replace the 16mm with 10mm. it's overkill at 16mm.

 

[pushrod]

could be cheaper to just reduce the size of the main earth lol maybe the last guy only had 16mm² on board or didn't know the regs for a TT


Edit - i really must type faster eh Tel? lol

 

[telectrix]

think your camshaft is getting worn , mate.

 

[pushrod]

think your camshaft is getting worn , mate.

Completely knackered mate - i need a rebuild

 

[telectrix]

i've just had my head skimmed. now my lug-oles are freezing

 

[topquark]

i've just had my head skimmed. now my lug-oles are freezing

Now you know how I feel .... all the time

 

[cyberjunction]

or replace the 16mm with 10mm. it's overkill at 16mm.

was thinking that

cheers - again thanks to all

 

[Octopus]

Do a search on "main protective bonding" there was a thread in the last couple of days which should help you.

 

[Deleted member 26818]

The actual size of the earth conductor doesn't matter.
It's the size that is required that matters.
So if after applying the adiabatic equation, it is determined that only 10mm² is required, but someone has installed 16mm². You still only need 6mm² for the bonding.

 

[Spudnik]

What he said^^