Hi

I will be having some work done on the lighting in the bathroom.
I am told that in order to get a Part P certificate the circuit will need to have a RCD on it.

So the main fuse box will have the 'old style' fuse replaced with a RCD and as part of that the two earth wire (one going to the gas pipe and one going to the main water pipe) may have to be replaced .

There are already earth cable going to the two pipes, what size do that have to be and how do I measure them ?

The repalceing the one for the gas pipe is not a problem as the pipe right next to the fuse box, the main water pipe is not !

Thanks

Hi in general the circuit protective conductor (main bond) from utilities ie gas 600mm from the inlet tap is usually 10mm. the main bond from the supply company is usually 16mm. it has to be unbroken from pipe to consumer unit. and labelled accordingly.
best bet for measuring is get a sample from B&Q or somewhere like that.

Almost!

The bond on the gas has to be within 600mm of the outlet of the meter and before any pipes tee off OR at the point of entry inside property

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Thankyou to every one that posted a reply, I think I undersant the requirement now in terms the size of the cable.
I googled it and thought 10mm cable would be an iron rod !

Is there a requirement two bonds ! i.e. water and gas

Yes the regs state that you have to bond the gas and water , the cable can serve both but must be UNBROKEN at the earth clamp ie looped round the screw and not cut .

Nick

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If it isnt broke dont bloody touch it until it bloody well is and if it is broke then make drawing of the connections before you remove the broken one and replace with a new one LoL

I was going to ask about joining earth cables but I think you've answered it here. I can't extend an existing cable to go from the CU to the water can I?

no i'm afraid you can't.

just to add to the other posts: -

when connecting the wires to the clamps for cross-bonding or single connections to the water/gas service, it is advisable to use lugs with a ratchet crimping tool. people that splay the cores & cram them into the clamp are not doing it properly. if you wiggle them they come out, lugged they do not.

I think there are slightly different rules for TN (TN-C-S or TN-S) and TT supplies. If the earth comes from the supply then you should ignore me. For a TT supply it may be OK to keep the old 6mm² bonding as per Figure 2.3 in the OSG.

If all circuits will be protected by RCDs or RCBOs, I don't understand why it is required to upgrade bonding conductors on TN systems when it is not required for TT systems with a local earth. Sure, if you want to have circuits without any RCD protection on a TN system then I can see the need for a chunky bonding conductor.