New Extension Earthing Questions

[digitrac]

Hi,

I am currently wiring (first fix) an extension and I have the following questions regarding earthing.

1) I have run a separate 16mm earth from the main earth connector block to a Utility Room, En-Suite Bathroom & Kitchen. I have done this to bond any pipes, radiators etc to earth. However upon reading threads on this forum it seems that this may be wrong and the cross bonding should be connected to the cpc of an adjacent light fitting. Could someone clarify?

2) A Combi-boiler has also been installed in a storage room with many pipes coming out the bottom. Do these need bonding together and to earth?

3) The Gas supply point has been moved - Is the best place to connect an earth as near to the house side of the gas meter as possible? I think the Gas companies side of the meter is plastic pipe into the ground

4) The water supply is also going to be moved and is again in plastic pipe into the ground. Do I connect an earth to where it becomes copper pipe?

Cheers

digitrac

 

[andy]

1) I have run a separate 16mm earth from the main earth connector block to a Utility Room, En-Suite Bathroom & Kitchen. I have done this to bond any pipes, radiators etc to earth. However upon reading threads on this forum it seems that this may be wrong and the cross bonding should be connected to the cpc of an adjacent light fitting. Could someone clarify?

bond the main water and gas services to the MET. ignore radiators

2) A Combi-boiler has also been installed in a storage room with many pipes coming out the bottom. Do these need bonding together and to earth?

cross bond each pipe coming out of the boiler. no need to connect to MET

3) The Gas supply point has been moved - Is the best place to connect an earth as near to the house side of the gas meter as possible? I think the Gas companies side of the meter is plastic pipe into the ground

not sure, but wether the gas/water company uses plastic or not, you must still bond if copper is used inside. also, how does your combi work since there is no gas?

4) The water supply is also going to be moved and is again in plastic pipe into the ground. Do I connect an earth to where it becomes copper pipe?

bond it where it enters the house. this to to be done regardless if the main supply is plastic or metal

 

[mapj1]

The CPCs of all circuits in the bathroom should be bonded to each other and to piping thast can be touched. no need if plastic pipes mean resitance to tru earth is >20K ohms or so. In kitchens (no naked bodies) this is not required.
Combi boiler should be effectively earthed through service earths, but if there is any doubt about pipe resitances, jointing compound or whatever, bond it - no one will fail you.
You are right about the gas, as near as possible to the meter, or as near to where enters house if meter is outside, all metal pipe that goes to fittings using the gas should form an electrically continuous earthed structure.

Water, earth the metal sections if they form a metallic loop with somewthing you can touch - taps or whatever, near entry point, or first exposed metal, is recommended (but on house side of any main isolator.)
hope that helps M.

 

[digitrac]

Thanks for the replies.

I think I know what I require but I'm still a bit unsure about point 1

To recap the four points and how I understand them:

1) Kitchen - Crossbond water and gas pipes together and connect to the MET

Utility Room - Crossbond water pipes together and connect to the MET

Bathroom - This is where I am unsure, do I either:

a) crossbond all pipes and towel rail together to all the cpcs in the room (namely lights and 2 shaver sockets)

b) crossbond just the pipework and connect to MET

c) some other solution?


2) Straightforward - Crossbond all the pipes going into the bottom of the boiler but do not connect to earth

3) Straightforward - Connect incoming gas supply from the point of entry to the house to the MET

4) Straightforward - Connect incoming water supply from the point of entry to the house to the MET

Please correct any of my assumptions!!!

also, how does your combi work since there is no gas?

The supply has been moved not disconnected

Many thanks,

digitrac

 

[mapj1]

As regards bath room, the idea is to cross-bond to CPC of all circuits that enter the bathroom. NOT THE MET, during fault circuit CPC (and so case of something you might touch like elcetric towel rail or metal light fitting bracket or whatever) will be higher voltage than MET, and pipes should be at the same voltage s metal work in the bathroom not necessarily same as MET. (4mm cable if exposed, 2.5mm if protected from mechanical damage by trunking/conduit etc.)

No special requirement for utility rooms or kitchens to be bonded, either to MET or local CPC, but you can do what you propose, if it is what you wish, and no-one will complain.
regards M.