Type of earthing to sub-board

[Spark123]

I posted the bathroom stuff as the OP said about bonding baths etc in the post above, which made me think he is getting confused with supp. bonding.
I was under the impression he has a new water main rising into the extension which is why I questioned the main equipotential bonding and the issue.

 

[JohnD]

OldSpark, I'm not sure I understand your plumbing arrangements. Can you clarify, please?

The water pipe going into the extension - is it supplied direct from the street on its own water meter, as an additional main? Or is it supplied through the existing incoming water main that supplies the original house?

I find it difficult to understand why an extension room would have the former.

Ta.

 

[OldSpark44]

I am getting some what confused now. The room is a utility room. I currently have a water main rising in one corner to which I am going to connect dishwasher, sink unit and tumble dryer - I could use PVC pipe work although I don't like it.


On the other wall I have a gas boiler (elec supply is from the main house) The boiler has been moved from an ajacent room therefore the existing has been extended by about 3m in length. The programmer for this boiler and thermostats/Motor Valves and pump are at the other end of the house. The earth bond is still on the gas pipe at the gas meter position as before and running direct to the meter position. The utility room has a new radiator next to the gas boiler and all pipework has been bonded between radiator and boiler - although I don't think this was necessary.

 

[OldSpark44]

The Water main arrangement:

The main watermain from the street comes into the house at the rear (PVC) a second PVC watermain has been directed into the new extension (also PVC) both are controlled from one stop cock in the pavement at the front of the house. The two watermain rise into the building at around 7m apart. The second water main was previously used for an old WC that has been pulled down and this new extension replaces.

 

[securespark]

If a property has more than one mains water feed that comes into the property independently of each other, then each should be MEB'd back to the MET.

As for your original question, when running a sub-main like this, I would always run a seperate earth in 16mm or larger.

 

[OldSpark44]

Hi securespark, You said:- If a property has more than one mains water feed that comes into the property independently of each other, then each should be MEB'd back to the MET. Thats strange as the local supply company inspector told me earthing one water main was adequate as long as both had cross bonding.

Regarding:As for your original question, when running a sub-main like this, I would always run a seperate earth in 16mm or larger. I have already run a 3 core 10mm SWA cable could I use the armouring as an earth, I am using the 3rd core as my earth to the sub-board. It's going to be a very length job now to run another earth wire as all the carpets have been fitted.

 

[securespark]

It's not strange - that's how I interpret the regulations.

If you have two independent stopcocks, then the pipework is obviously not connected to each other, therefore you have no continuity from one side to the other. They should be bonded individually back to the MET, regardless of what the "supply company inspector" thinks!

Were you born in 1944? What edition did you last work under?


As for the earthing, I would not rely on the armour to provide a reliable earth path, and the core is not big enough. That is why I always run a seperate conductor. in your case, though, it may be too late!

 

[JohnD]

As regards the water mains, my mental picture is that the supply comes from the pavement into the house, and that is your incoming main. I am picturing the water supply to your other room as being a branch off this supply, so it seems to me that is is not an incoming main. Especially as it is controlled by the same pavement stopcock.

However I haven't come across the situation you describe.

 

[securespark]

I understand it as I have previously described - otherwise how can you protect one side (of the pipework installation) if it is isolated from the other?

As I understand 7671, you must bond the cold water pipe to the MET within 600mm of the stopcock. Now, if your installation has two rising mains, and two stopcocks, you must have two MEB's to the pipework, no?

 

[Spark123]

This is how I envisage the water mains setup:

 

[securespark]

Can you tell what it is yet....?

Yes, that's as I see it from OS44's description.

In which case, both pipes need bonding, don't they?

 

[OldSpark44]

Hi Spark123, yes your diagram is correct, I have started lifting all the carpets, I hope to get the extra earth wire in my Sunday night. Thanks guys for all your help/advise

 

[RF Lighting]

This is how I envisage the water mains setup:

Is there a wasps nest in that chimney?

 

[OldSpark44]

Sorry I should have said thanks to RF Lighting for the diagram.