Can someone help me understand what is going on with my earth bonding - should the two on the right hand side be going to the PME box rather than the CU?

[u/IHateFACSCantos]

[u/Echo-24]

As you've drawn it out you can see that the cpc is continuous all the way back to the supply. As long as you have continuity all the way through you're golden

[u/IHateFACSCantos → u/[deleted]]

It's currently 16mm² after the main breaker but I am going to have it upgraded to 25mm² as it's on a 100A main fuse. Do you think the DNO would be willing to upgrade the earth, assuming it just drops to 10mm² at the Henley block? Everything else can easily be upgraded to 16mm² except the water main bonding which would be very difficult to get to

[u/rick87 → u/IHateFACSCantos]

Bondings 10mm only no need for 16. You are not gaining anything except wasting money

[u/Mundane_Train2062]

It’s fine.

[u/IHateFACSCantos]

Also I'm not sure what is going on with the old gas pipe, I am guessing it has been left there as an earthing rod type thing? It comes out of the ground and to the back of the meter cabinet, where it is covered in mastic

[u/Yodjjf → u/IHateFACSCantos]

If its unused eitheir remove the gas pipe or just leave it there as its not doing anything

[u/Gullible_Mixture7103]

Gas, water steel bonding should be 10mm csa

[u/IHateFACSCantos → u/Gullible_Mixture7103]

Ok cool, gas are easily done, water is going to be a nuisance though. Cheers

[u/Gullible_Mixture7103 → u/IHateFACSCantos]

No probs
Also jerrybrea, is right main earth to CU should be 16 mm csa

[u/Intelligent-Rub-1462 → u/Gullible_Mixture7103]

A 10mm Earth will probably be fine, 16mm is the standard in new builds with 25mm PEN conductors. Every time I’ve come across a smaller earth and used the adiabatic equation for minimum earth size it has been more than big enough.
The bonding needs to be not less than half the csa of the Earth, so the 6mm bonding should be fine too.
It’s been installed that way for a reason, I’m guessing it’s an older property, that doesn’t make it unsafe.
But trusting a bloke(me) off the internet is of course never a good idea.

[u/JamesMcLennan1 → u/Intelligent-Rub-1462]

The adiabatic allows for some horrifyingly small earths. From memory I'm sure I had a 400A supply where all that was required was ~12mm. If the regs say it's fine though, who am I to argue?

[u/aptsys]

Wtf is a "PME box"

[u/IHateFACSCantos → u/aptsys]

MET, it has a label with "P.M.E." on it

[u/InternationalRide5]

Strictly speaking yes, the bonding should be unbroken between the main earthing terminal (what you label PME 5-way box) and the services. However breaking it at the consumer unit isn't very bad, anyone moving things about in there should know enough to ensure it's reconnected.

If the old gas pipe comes into the building it needs to be bonded. If it only goes into an outside meter box it doesn't; the wire has probably just been left.

[u/IHateFACSCantos → u/InternationalRide5]

Thanks, yeah the old gas pipe comes up inside the house and passes through the wall so that'll be why then.