Earthing Arrangements Explained + Photo's

[Paul.M]

This is for the people still in or has just left their electrical education or for those of us that need a refresher in domestic earthing arrangements. It's all very well looking at prity diagrams in college and in books but its different when your out in the field for the first time. Hope this thread helps you and I hope that other members will post up their pictures of main incomers/earthing so others can learn and understand this subject better. I wish I could refer to something like this when I was in college.



First of all we have 3 types of earthing arrangements, TN-S, TN-C-S and TT.

TN-C-S

This is where the main earth cable from the main earth terminal (met) is connected to the neutral at the suppliers main fuse. A good way to remember the name of this arrangement is to think of the C meaning COMBINED.


TN-S

This is where the main earth cable from the met is clamped or solderd to the steel of the SWA or the led outer sheath of the incoming supply cable. Again a good way to remember this is to think that the S stands for SHEATH.

TT

The main earth cable from the met is connect to an earth electrode (aka earth rod). This is because not all properties are supplied with a TN system by the supplier so we have to insert a rod into the ground.


Notice how the earth cable on the TN systems go back to the main incomer, one goes to the main fuse (TN-C-S) and the other goes to the incoming cable (TN-S). If the main earth cable doesn't go back to the fuse or incoming cable it will be a TT. This is the simplest way I can put it without going into extended detail.



Now that we've seen some prity diagrams (am I starting to sound like a teacher lol) we will now look at real world photos that are not as straight forward as the diagrams.


First example, is it a TN-S or a TN-C-S or both?

 

[Dave 85]

To be quite honest, and I know, this is a running joke and we always say it, but this time I can, hand on my heart, say that the cut out seal had already been removed before I got there.

 

[Top Cat]

Just a quick point as this is for training purposes Paul, on the drawn TT system someone may think that water and gas do not need earthing! I know it's a stupid point but someone will..................!

Edit:- As kindly pointed out to me it should read bonding not earthing!

 

[telectrix]

TC... that TT system has all plastic water pipes and there is no gas.

 

[Paul.M]

To be quite honest gents I want other members to say things like what TC has said on this thread to expand it into a great source of information for everyone. Please continue with positive posts.

 

[Dave 85]

To be quite honest gents I want other members to say things like what TC has said on this thread to expand it into a great source of information for everyone. Please continue with positive posts.

Wow man, I must be the new Derren Brown, I just influenced your actions without you realising it. I start a post with 'to be quite honest' you 'like' it and then you start your next post with 'to be quite honest'.
Nuts to this electrics lark Im going into mind control.....

 

[topquark]

To be quite honest gents I want other members to say things like what TC has said on this thread to expand it into a great source of information for everyone. Please continue with positive posts.

Why? Are you covering DC systems as well?

 

[Knobhead]

Why? Are you covering DC systems as well?

Do you want me to start on that?

 

[Knobhead]

Just a quick point as this is for training purposes Paul, on the drawn TT system someone may think that water and gas do not need earthing! I know it's a stupid point but someone will..................!

Edit:- As kindly pointed out to me it should read bonding not earthing!

Can't be doing with fussy cats

View attachment 13130

 

[Top Cat]

Can't be doing with fussy cats

View attachment 13130

Size of earth wires?

You'l wish soon you hadn't asked for criticism!

 

[Paul.M]

Let's just keep to domestic earthing systems for now lads. I know this is basic stuff but its somewhere that the learners can Google and learn more than in a book from us lot.

It's worth the effort IMHO.

 

[Air Conditioner]

Thanks for this thread its great to see some real life pictures, rather than just the pictures in books. One thing that took me by surprise in the transition from books to real life was that the main earthing terminal is sometimes in the CU in real life, rather than a totally separate earthing bar which how it is normally illustrated.

 

[telectrix]

that used to be the norm years agoo. it's only in the last 10-20 years that a separate MET has become more widespread.

 

[Air Conditioner]

Is there a reason for this? Is it easier to measure Ze? Or the manufacturing of cheaper CU's? Or is it just the way it is?

 

[Top Cat]

What are those yellow, blue and black things!:biggrin5:

You did say you liked what TC was doing! Lol

 

[Paul.M]

Air conditioner and Tel, these are the things that I'm on about. It's great learning from books to pass an exam but its a different world out there once you pick up your tool box and go to your first job.

Has any other members got main incomers photos? Post them up.