Equipotential Bonding - Again...

[Joe4542]

Hi,
Sorry if I'm asking the same question that has been asked before, but I do find this quite a confusing subject and there are many differing answers .
I'm re-doing my kitchen and have moved some of the pipework but need to check the Earthing arrangements - I understand that the Kitchen itself does not normally need supplementary bonding, but just want your views on the current setup.
It's an upstairs maisonette, with some fairly old wiring down at the CU, but it does look like some extra earths were fitted not so long ago. I think I need to do the main 10mm earth to the gas meter down in the CU cupboard since I cannot see any in the cupboard, and the new gas meter we had fitted last month got a sticker from the fitter saying he cannot see any Equipotential bonding to our pipes - buts thats another part.
Our water main - its a lead pipe coming into middle of house from downstairs flat, which I've joined downstairs to copper pipe via a 'Lead-Loc'. This copper pipe runs under the kitchen floor to the back of the house, where it comes out of the floor to a new stopcock I've fitted. Since this it the first accessible point in the flat - This is where I would attach my 10mm earth which runs up from the CU ?

This 10mm earth which was previously attached to some of the pipes, was also run along all 5 of my combi boiler pipes - CH FLOW, DHW, GAS SUPPLY, MAINS WATER, CH RETURN.

Would I be best to do the same and run the 10mm Earth that I attach straight by the stopcock, over to the 5 boiler pipes, even tho one is already then attached (MAINS WATER)? ... OR would it be ok to cross link the 5 pipes together with 4mm Earth (using the Combi Mains in for Earth).
With the earth wire - I'm not sure my 10mm main will be long enough to reach - is it OK to join with another piece or what?? Would normal Metal Earth block be OK for this?

Does everything above make sense to you - hope so...and that you can try give me some advice - there are so many different threads around that I dunno what way to go!!

Thanks in advance!
Joe

 

[JohnD]

what a long post!

You need several things:

Main Bonding:
from the Main Earthing Terminal which may be inside your Consumer Unit, or a terminal block close to the meter and CU, 10mm G&Y to the incoming Gas and Water Mains, on your side of the meter and main stop-cock. This 10mm should not have joints in it (unless they are made permanent,e,g, by soldering) because it is vitally important that it does not come loose or high-resistance, so if yours is too short you should buy a longer piece. There should also be a 16mm G&Y going into the Consumer Unit Earth block, from the source of your Earth. This is most often provided as a terminal by the Electricity Company where their incoming cable is terminated in a large plastic block.

Supplementary Bonding
This is required in the bathroom, to connect the earth wire of all the electrical circuits entering the bathroom, to all the metal pipes that enter the bathroom. this is done in 4mm G&Y but you can use larger if you have it handy.

Also, the boiler should have (this is not an Electricity regulation, but instructions about the boiler) all the metal pipes into and around it, bonded together so that the boiler engineer is protected against shocks, and connected to the earth wire of the electricity circuit that supplies the boiler.
I would expect this to be done in 4mm but you can use larger if you have it or the instructions say so.


To make it easier to follow your question, can you ask separately for Main, Supplementary, or Boiler, please. This will help stop us confusing each other. If you can post some pictures that will help us see what you're doing.

 

[davy_owen_88]

With the earth wire - I'm not sure my 10mm main will be long enough to reach - is it OK to join with another piece or what?? Would normal Metal Earth block be OK for this?

No. Main bonding conductors must be a single unbroken length between the pipe and the MET.

Our water main - its a lead pipe coming into middle of house from downstairs flat, which I've joined downstairs to copper pipe via a 'Lead-Loc'. This copper pipe runs under the kitchen floor to the back of the house, where it comes out of the floor to a new stopcock I've fitted. Since this it the first accessible point in the flat - This is where I would attach my 10mm earth which runs up from the CU ?

The bonding clamps should be accessible for inspection and testing, so where it emerges from the floor is the best place.

 

[Joe4542]

OK, Thanks guys.

Main Equipotential Bonding
I shall need to add my own 10mm earth from the MET to the Consumer side pipe of the Gas Meter in the same cupboard as the meter. TO DO

Then I shall attach the Already Run 10mm Earth cable - in one piece to my Mains Water pipe where it comes out of the floor into the kitchen.
That will be the sole connection to this wire in the kitchen?

Supplementary Equipotential Bonding - BOILER - Not normal Suppy bonding
I shall link the 5 pipes below the boiler (CH FLOW+RETURN, DHW, GAS, MAINS) with 4mm Earth and attach this to the Boiler chassis - would this do rather than trying to connect the 'Fairly Heavy' 4mm wire into the Boiler's earth terminal (The FCU that I'm using isn't really accessible - plastered around). Failing that I'll probably have a junction block mounted onto wall under boiler where my 2.5mm T+E comes out from FCU along wall, ans joins with the flex from boiler itself - could try join earth in there too>.

Also would I still connect the suppy 4mm to the Mains + Gas on boiler? since they're already connected elsewhere - I've read references to resistances + differing potentials that could be introduced - or am I getting crossed with the normal purposes of the bonding I'm doing in first place??
Hope this is clearer

Ta - Joe

 

[JohnD]

Main Equipotential Bonding

That will be the sole connection to this wire in the kitchen?

Yes

- BOILER -
I shall link the 5 pipes below the boiler (CH FLOW+RETURN, DHW, GAS, MAINS) with 4mm Earth and attach this to the Boiler chassis - would this do rather than trying to connect the 'Fairly Heavy' 4mm wire into the Boiler's earth terminal (The FCU that I'm using isn't really accessible - plastered around). Failing that I'll probably have a junction block mounted onto wall under boiler where my 2.5mm T+E comes out from FCU along wall, and joins with the flex from boiler itself - could try join earth in there too>.

Sounds like that ought to be in a Flex Connector ( a standard white accessory, same size as a socket outlet and fits the same back box - a couple of pounds at an electrical supplier) not a junction block(?)

Connect it to the Earth terminal on the connector block where the power comes into the boiler, if you can. If you can't reach it, leave a reasonable length of 4mm G&Y and ask the boiler Engineer to connect it next time you have it serviced. You can buy a 4-way earth block for about a pound. I would prefer to see it at the FCU, but Gas rules are beyond me.

Also would I still connect the suppy 4mm to the Mains + Gas on boiler?

don't understand the question.

 

[Joe4542]

Johnd,
I went for a straight Fused connection unit since I didn't want the flex coming out of the faceplate over to the boiler, so have run the wire from the FCU, through conduit in the wall (now plastered over), to behind where the boiler is mounted so it comes out of the wall - hidden by boiler. Just will use a connector block/JC to connect the 2.5mm T+E from wall to flex already wired into boiler.

I was just querying if I would still cross-link the Gas + Mains water pipes below the boiler, with the other 3 pipes - when they would already by Equi' Bonded elsewhere...

Thanks
Joe

 

[JohnD]

I was just querying if I would still cross-link the Gas + Mains water pipes below the boiler, with the other 3 pipes - when they would already by Equi' Bonded elsewhere...

yes. the boiler engineer wants to be able to see when he works on the boiler that everything is cross-bonded, to give him condidence that he won't get a shock if he has one pipe in one hand, and another pipe in the other hand, while leaning on the boiler casing.

 

[Joe4542]

Ok, Thanks for all your help - I can now start to tidy up some of the mess that was there before - happy that I'm not making things worse than they were.
I'll have to confirm I don't have my Gas Pipe bonded to MET, and if so - add that to my ever increasing TODO list.

Thanks Again
Joe

 

[Paul Barker]

[
yes. the boiler engineer wants to be able to see when he works on the boiler that everything is cross-bonded, to give him condidence that he won't get a shock if he has one pipe in one hand, and another pipe in the other hand, while leaning on the boiler casing.

Do you know what John, I've never given it a second thought.

I suppose I really should check pipework for live before I start work on a boiler.

A cat 5cable runner was telling me he was at a factory trying to find the huge spike on his scope, when he suddenly realised it was a 50hz. He so discovered that the metal framework of the building was at 230v. Straight away he told the resident sparks, who told him it was crap, he (the sparks) got up on his aluminium step ladder touched the metal framework, there was a bang and he was thrown off the step ladders.

 

[securespark]

We are all issued with volt sticks. The sole use of these volt sticks is to check appliance casings, metalclad accessories & such like to make sure they are not live before we touch them...