Currently reading:
Earthing Arrangements Explained + Photo's

Discuss Earthing Arrangements Explained + Photo's in the UK Electrical Forum area at


Reaction score
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.


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.


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.


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?

Last edited:
It's a semi-detached house with a pre-paid meter and cut out within the same enclosure (I think!).
The property is some distance from me so I'll ask the client (a friend) for another picture showing the content of the enclosure and when I get it I'll post it here.
Deleted... only I haven't worked out how to delete the photos! Help!!


  • DSC_0123.jpg
    289.9 KB · Views: 124
  • DSC_0125.jpg
    299.2 KB · Views: 112
  • DSC_0126.jpg
    316.2 KB · Views: 114
Last edited:
Though it might be that. Don't assume it's 415V because it says it on the side. In a similar way, don't assume it's a 100 amp fuse because it says 100A on the fuse carrier. Daz

Reply to Earthing Arrangements Explained + Photo's in the UK Electrical Forum area at


Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
This website was designed, optimised and is hosted by Operating under the name Untold Media since 2001.
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock