Adding an Earth Rod on a TN system and BS7671

[ianmacd]

So this has been dragging on between a few of us for a lot of posts over a few threads (and years) so I thought I would start a poll to see what people think.

I would ask that you read 542.1 FULLY before voting on this though even if you believe you know the answer already.

The proposed install is an earth electrode (with appropriately sized cabling) to the MET on a TN system in a domestic property.

Thanks.

Ian.

 

[Andy™]

7671 does not clearly state either way, but i cant see anyway in which it could make the installation more dangerous (since bonding metallic services is basically the same thing)

 

[ian932]

[quote name='Andy

 

[ianmacd]

I agree having a lead water pipe bonded with a 10mm is one dirty great rod. In the republic of ireland it is regulation to fit a rod on a TNCS. no Irish joke please

Regulations on the DNO equiv or on the installer?

 

[Adrian]

I just finished a new build were the dno gave me a temp supply which I TT then when the installation was complete I ask them to connect my tails into their meter I also asked for pme when I went back to the job they had pme d it but also connected my rod to there pme

I asked my nic inspector about this and he said it was fine and if anything better

 

[m4tty]

lol i love this forum. Such a crack up. Keep it up

 

[Adrian]

I think reg 542.1.5 answers your question

 

[batty]

Can't see why you would want to TT as well if you have pme earth takes all sorts though.

 

[ianmacd]

I just finished a new build were the dno gave me a temp supply which I TT then when the installation was complete I ask them to connect my tails into their meter I also asked for pme when I went back to the job they had pme d it but also connected my rod to there pme I asked my nic inspector about this and he said it was fine and if anything better

Where had they connected it?

 

[green-hornet]

I have voted yes BS7671 does allow this, simply because I see nothing in the regulations that say you can not.

If it was an issue there would be a section which would state "do not rod a tn system".

 

[ianmacd]

I have voted yes BS7671 does allow this, simply because I see nothing in the regulations that say you can not.If it was an issue there would be a section which would state "do not rod a tn system".

Did you fully read 542.1 (particularly 542.1.1 that states ONE of the methods in .....)?

 

[green-hornet]

best section 542.1.5

 

[ianmacd]

best section 542.1.5

What are you trying to say there?

Also check out the Note in 411.4.2.

 

[steptoe]

I just finished a new build were the dno gave me a temp supply which I TT then when the installation was complete I ask them to connect my tails into their meter I also asked for pme when I went back to the job they had pme d it but also connected my rod to there pme I asked my nic inspector about this and he said it was fine and if anything better

how do you know it is PME?

is there a label on cutout?

Im not surew of regs now but it used to be always had to be labeled as such.

Can't see why you would want to TT as well if you have pme earth takes all sorts though.

cos TT is the superior installation method, even though some (incompetent) people decide to TT and try to keep TNCS even thought they have upgraded.

I have voted yes BS7671 does allow this, simply because I see nothing in the regulations that say you can not.If it was an issue there would be a section which would state "do not rod a tn system".

and where does it say you are allowed TWO earthing systems?

I am sure I will find a reg in the big red comic that specifically disallows it.

and with this ongoing topic I am going to have a look at it more than twice this year.

IT IS PROHIBITED

to have more than one earthing system

 

[Andy™]

and where does it say you are allowed TWO earthing systems?

I am sure I will find a reg in the big red comic that specifically disallows it.

and with this ongoing topic I am going to have a look at it more than twice this year.

IT IS PROHIBITED

to have more than one earthing system

which reg says its prohibited? all you seem to do these days is make stuff up, but with no backing.

 

[ianmacd]

If you vote Yes or No please back it up with your reasoning.

 

[Adrian]

how do you know it is PME?is there a label on cutout?

they connected it up at the cut out

and there was a label

REG 542.1.2 TN-S

REG 542.1.3 TN_C-S

REG 542.1.4 TT

REG 542.1.5 The earthing arrangements may be used jointly or seperately for protective and functional purposes according to the requirments of the installation

 

[ianmacd]

So what does 542.1.5 mean to you as I read that as whichever ONE of the other 4 you have/choose can be used as both functional and protective purposes.

 

[Adrian]

to me it means you may use one or a combination of the earthing systems, but which ever one you use, any protective conductors must be capable of carrying the maximum fault current likely to flow

REG 542.1.8

also if you look at table 54.1 they talk about pme and earthing conductors buried in the ground without protection against corrosion ( which to me means a cable without a sheath, a bare conductor ) REG 542.3.1

 

[ianmacd]

So to summarise you have not found a reg that says you can rod a TN supply at the MET despite voting that way?

Interesting.