Earth wiring

[blondini]

On tracing my wiring I've found a few scary things. The main earth from the CU just connects (loosely!) to a cold water pipe. It's in the same room as the stopcock, but not directly 'near' the stopcock. (There is no supplier earth so I've already asked them if they can provide a PME but it's going to be weeks before I get an answer). The incoming water is on lead pipe and the stop cock is a soldered joint to the copper internal piping. I know I have to bond unbroken from CU back to the stopcock, but I guess there's probably a decent earth there anyway?

The question is, do I need to knock in an earth rod or is it ever ok to use the water main?

There's also an earth bond iacross all the piping to the combi. It's on an unbroken 16mm cable back to the CU. If I do need an earth rod, can I connect it directly to this cable, and should it be disconnected from the pipework bonding to leave that as supplementary? The combi is in a kitchen where the sub flloor is nice and damp so it's possibly a good spot for a rod.

 

[luminaire]

Can you post a photo of your incoming supply?

If your supply is T-T (usually overhead) you would expect an earth electrode - however this is not connected to your pipework so under no circumstances would yo connect an earth to your pipework.

Your main equipotential bonding should 10mm to your stopcock It looks as though when your boiler was installed the plumber bonded it with 16mm.

It would be better to get your system on PME and get get your main bonding sorted out, you might even get them to do it if you ask nicely. Better still tell them you got a tickle off your taps or something like that. They might come out pronto!

 

[blondini]

Cheers for the reply. I can't post a photo, but it's an old property and although it's definately an underground feed, no overhead anywhere in the street, there is no earth connected to the incoming cable in any way shape or form, and no earth electrode either. There are just two earth cables running from the CU as described and as I said, I'm waiting for the supplier to confirm if they can provide a PME. I don't want to invoke Mr Tickle as I don't want them to come out and condem my wiring just yet.

Meanwhile to make it safer, I'll knock in an earth rod and connect that back to the CU, right? I'm a little confused about the supplementary stuff. Are you saying that I should disconnect the cross bonding at the combi from the CU and connect it to the stopcock instead? And should the bonding from the incoming gas supply at the meter be treated similarly?

 

[davy_owen_88]

Meanwhile to make it safer, I'll knock in an earth rod and connect that back to the CU, right? I'm a little confused about the supplementary stuff. Are you saying that I should disconnect the cross bonding at the combi from the CU and connect it to the stopcock instead? And should the bonding from the incoming gas supply at the meter be treated similarly?

Adding an earth rod without sufficient testing may well be a waste of time if you can't test that you have made good contact.

If you have access to the water stop cock then that should be connected to the MET with 10mm^2 cable - same with the gas. Cross bonding is usually done in 4mm^2 but is not run back to the MET so its possible your plumber did both at the same time.

Gas and water pipes used as the main form of earthing have not been acceptable for many years, although you may well be getting good contact.

The best advice I can give you is to call a sparks in. They can test the earth rod to ensure it makes good contact and they can upgrade your main incomer at the CU with a time delayed 100mA RCD (bringing it up to standards for a TT supply). They will also upgrade all the MEB conductors and check supp. bonding at the same time. These jobs will be needed when you are upgraded to PME anyway.

Davy

 

[comms]

Adding an earth rod without sufficient testing may well be a waste of time if you can't test that you have made good contact.

Agree with you on that one

If you have access to the water stop cock then that should be connected to the MET with 10mm^2 cable - same with the gas.

Yes agree


Cross bonding is usually done in 4mm^2 twin and earth .

Dont think so

 

[davy_owen_88]

Grr, too damn fast for me I really should read through my posts looking for stupid mistakes not just spelling errors.

Davy

 

[comms]

Grr, too damn fast for me I really should read through my posts looking for stupid mistakes not just spelling errors.

Davy

It's easily done Davey me old mucker

 

[bernardgreen]

The incoming water is on lead pipe .

Yes you need that to be replaced for health reasons. Let the water flow for a bit in the morning before you take any for drinking.

It may only be a short length to a plastic main but it MAY be the best TEMPORARY earth you can get until the PME is provided.

You could ask the water company if it is metal all the way to the main in the road. If it is then [a] it probably is a good "earth rod" and you can ask them to replace it on health grounds after the electrics have been up-graded.


Bernard
Sharnbrook

 

[securespark]

First, you cannot supply your installation with an earth from the water pipe, not since 1966.

BERNARD, WHAT ARE YOU SAYING???? - It may be the best temporary earth, mate, but you cannot sanction its use!

A gas pipe may be even better, but you cannot allow that either. It has never been permissible to use the gas pipe as an earth source.


Second, there is no mention of a 30mA RCD. If this is a TT supply with potentially sky-high Ze, an RCD is essential.

Without it, the installation and its users are AT RISK.

There are countless 1000's of underground TT supplies in Staffs with no means of earthing.

Third, you do not strictly need 10mm² for MEB's on TT, but point taken. If you upgrade to PME, you will need 10 minimum.

 

[bernardgreen]

BERNARD, WHAT ARE YOU SAYING???? - It may be the best temporary earth, mate, but you cannot sanction its use!

I did say MAY be and TEMPORARY

Better to have some earth than nothing at all provided there is an RCD to react.

The regulations are there because most water supply pipes are plastic and the average person has no idea what brings the water so it has to be a blanket ban on using water pipes.

 

[securespark]

Better to have some earth than nothing at all provided there is an RCD to react.

But we don't know there is one, do we?

The regulations are there because most water supply pipes are plastic and the average person has no idea what brings the water so it has to be a blanket ban on using water pipes.

Were most water supply pipes plastic in the 60's? I don't think that's the sole reason for the regulation.

I think it had more to do with not having to rely on one service for the provision of another.

 

[luminaire]

Cheers for the reply. I can't post a photo,

To upload an image;
Go to a hosting site such as imageshack: http://imageshack.us/
Click browse and locate the image. Ensure resize image is ticked and select 640 x 480 (for message boards). Click host it.
After the image has uploaded imageshack displays a list of links to the image. Highlight the text in the line at the bottom of the screen "direct link to image" and copy the text (press CTRL C to copy).
On your post type

and insert the text from imageshack inbetween the two (press CTRL V to paste), so it reads something like:
{img]http://img404.imageshack.us/img404/4748/dolrwo4.jpg[/img}
When you submit your post the image should now appear.

This appeared in yesterday's post by Spark 123

If you could manage one it might help loads.
Best of luck