PME from TT to be installed but water/gas earthing required

[Invisible-Man]

Hi I have had the DNO visit today for a check before updating to PME from TT, they said that I have to earth bond the gas and mains water pipe (although blue plastic before coming into property) in 10mm first to meter board earth block, and consumer unit 25mm to meter board earth block before doing the upgrade, now the question is, can the mains water pipe be earthed at any point in the property, and also do the mains water and gas have to be seperate until meeting at the meter board earth block or can they be linked together early on, and then run as a single 10mm to the meter board earth block, I just thought I would ask as it would be more convenient this way. One last thing, does this have to be done by a qualified electrician under the new legislation or can this be done without qualification.

Many thanks

 

[securespark]

The MEB's should be no more than 600mm from the meter or stopcock and before any branches.

Don't clamp to lead or flexipipe.

 

[JohnD]

Anyone can do it

You have to Main Bond the incoming services within 600mm of them entering your property, on the consumer's side of the meter and stopcock.

The earthing wire must not have joins in it, it must be a continuous length.

However, if the gas and water pipes are on the same side of the house, it is possible to use the same length. At the first pipe you come to, you strip off a section of insulation without cutting the wire, wrap it round the earthing bolt and trap it with the tabbed washer (if you look at a bonding clamp you will see what I mean), then continue the wire on to the second pipe. You may, though, find it less trouble to run separate wires.

You can bring all your earth wires together at the earth bar in the consumer unit; or, if it is tight or inconvenient, you can bring then together at an earth block like this, with the wire to the Supply Head and the Consumer Unit also joining here.

4-way is the minimum size but an 8-way gives more room. They are very inexpensive.

You have to fasten a permanent label to it saying it is the electrical safety connection and must not be removed - you get such a label with every earth clamp so this is the easiest way to get one - they are embossed metal.

 

[Invisible-Man]

Anyone can do it

You have to Main Bond the incoming services within 600mm of them entering your property, on the consumer's side of the meter and stopcock.

The earthing wire must not have joins in it, it must be a continuous length.

However, if the gas and water pipes are on the same side of the house, it is possible to use the same length. At the first pipe you come to, you strip off a section of insulation without cutting the wire, wrap it round the earthing bolt and trap it with the tabbed washer (if you look at a bonding clamp you will see what I mean), then continue the wire on to the second pipe. You may, though, find it less trouble to run separate wires.

You can bring all your earth wires together at the earth bar in the consumer unit; or, if it is tight or inconvenient, you can bring then together at an earth block like this, with the wire to the Supply Head and the Consumer Unit also joining here.

4-way is the minimum size but an 8-way gives more room. They are very inexpensive.

You have to fasten a permanent label to it saying it is the electrical safety connection and must not be removed - you get such a label with every earth clamp so this is the easiest way to get one - they are embossed metal.

Thanks for that, do you think that 10mm is a bit over the top? Also 25mm from consumer to earth block seems a bit on the large side, I am sure an earth bock like the one you show will only take 16mm thats without connecting 25mm into the consumer unit, what do you think?

 

[JohnD]

10mm is REQUIRED for main bonding.

The supplier can tell you to use 25mm, they may have good reason, I don't know, (many domestic installations use 16mm) but this should be a fairly short piece and they are entitled to insist.

The earth blocks usually have extra-big holes at the end. I can't be bothered to find a bit of 25mm and try it though. In the old days we sometimes used to spread the strands of the conductors out into a fork and put half into one hole and half into another.

You can also get a little brass converter that takes in 25mm or 35mm cable and has a solid prong the next size down. Otherwise it might need a crimped connector but this is in a large size that domestic people don't usually have.

 

[Invisible-Man]

Thaks John, I think from your kind help I have got it all under control !!!


Many thanks

 

[securespark]

put half into one hole and half into another.

fnarr, fnarr!


But joking aside, the main earthing conductor (from supply cable or cut-out) is generally 16mm2, and MEB's are 10, supplementary 4. Sometimes on PME, the REC ask for 16 MEB too. But not 25.

PS Up yours, John!! Beat you to it....

Sorry. Missed one:

if it is tight or inconvenient,

fnarr, fnarr!

Think that's quite enough Finbarr Saunders for one evening....

 

[JohnD]

fnarr, fnarr!

Has Mrs Secure gone back to stay with her mum? Sounds like you're missing her

 

[securespark]

No....my schoolboy SOH is coming out...Friday afternoon and all that.

 

[JohnD]

They seem to be asking for 25mm Main Earthing Conductor (not MBs), maybe the property has 35mm P+N tails? Unusual perhaps. Or some other strange reason.

 

[Spark123]

I would have thought 16mm² would be adequate for main circuit protective conductor even if the tails were 35mm²??? Seems like a strange combination to me, but then again the DNO have seen the premises and there may be some reason for this.

 

[Invisible-Man]

Over head cable coming in, single core 35mm, tails are 25mm with a 100amp DNO fuse. I do not mind using the 25mm earth as you are only looking at 1 metre, its just the large bore fitting thats the problem

 

[plugwash]

aren't earth blocks usually designed for 25mm in the ends and 16mm in the other terminls?

failing that then as others have said you can just split the cores between two terminals, no big deal.

 

[Invisible-Man]

aren't earth blocks usually designed for 25mm in the ends and 16mm in the other terminls?

failing that then as others have said you can just split the cores between two terminals, no big deal.

Yes sure, I fitted another earth block recently and am sure that the bigger holes only take 16mm with the rest taking 10mm, it would be interesting if anyone could confirm this! Perhaps the time has come where they will have to start making larger ones !!!

 

[JohnD]

perhaps

it's only a block of brass!