Earthing Arrangements Explained + Photo's

Paul.M · Jun 25, 2012

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

[ElectriciansForums.net] Earthing Arrangements Explained + Photo'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?

zap · Jan 23, 2014

DPG said:
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

Yeh, sorry, my system went a bit lala for a few minutes. I don't assume anything. Assumptions bite! But point taken...

Engineer54 · Jan 23, 2014

That's the BS fuse voltage rating.... lol!!

zap · Feb 12, 2014

DPG said:
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

Right you are, not to assume.
After obtaining some temporary seals from the DNO I looked inside the carrier and this is what I found.

Brush
30 Amp
60 LR
Certified
440V AC 4
BS88 - 1952
Class 3
Made in England

The print on the fuse had faded so there may be errors in the above info.

The DNO were contacted again and they're sending an engineer to address the issue.

Engineer54 · Feb 12, 2014

Just shows you how long that service fuse has been in place. My parents house only had a 40A service fuse and a 40A meter for donkeys years. Then got updated out of the blue to 60A fuse and 100A meter. Later still, Mechanical meter replaced with digital meter and fuse/tails uprated to 80A/16mm....

Silly Sausage · Feb 12, 2014

Brush
30 Amp
60 LR
Certified
440V AC 4
BS88 - 1952
Class 3
Made in England

Non of your Chinese rubbish!

Engineer54 · Feb 13, 2014

Archy Styrigg said:
Non of your Chinese rubbish!

lol!! Ah, ...But for how long??

GLENNSPARK · Feb 13, 2014

Engineer54 said:
Just shows you how long that service fuse has been in place. My parents house only had a 40A service fuse and a 40A meter for donkeys years. Then got updated out of the blue to 60A fuse and 100A meter. Later still, Mechanical meter replaced with digital meter and fuse/tails uprated to 80A/16mm....[/QUOTE]

and it held for all that time....

which begs me to ask what the point in this excercise was?

Knobhead · Feb 13, 2014

Archy Styrigg said:
Non of your Chinese rubbish!

What happened to Brush Engineering?

I had the misfortune of installing one of their LV panels. Biggest pile of junk I’ve ever come across. So bad I got division engineering involved and we chucked all the outgoing switches away. Replaced them with System 4 gear.

GLENNSPARK · Feb 13, 2014

Tony said:
What happened to Brush Engineering?

I had the misfortune of installing one of their LV panels. Biggest pile of junk I’ve ever come across. So bad I got division engineering involved and we chucked all the outgoing switches away. Replaced them with System 4 gear.

hmm..

well heres a famous product out of Brush`s loughborough works:

and something from BR Derby....but with Brush electrical plant & gear:

each gave 30 years of good service...the only issues were with the Sulzer twin bank diesel engines they used

Silly Sausage · Feb 13, 2014

I've got a fantastic book, 'Diesel Traction. Manual for Enginemen', 1962, great book.

Also got one for 'Railway Steam Locomotive Enginemen'. More of Geordie's era.

Geordie Spark · Feb 13, 2014

Archy Styrigg said:
I've got a fantastic book, 'Diesel Traction. Manual for Enginemen', 1962, great book.

Also got one for 'Railway Steam Locomotive Enginemen'. More of Geordie's era.

I have that one and I have "2750 - Legend Of A Locomotive" which is a fictional story about an A3 Class Gresley Pacific named "Papyrus" that I've seen many times written by H.C. Webster. (I think I have some for diesel as well but let's not go there!)

I first stumbled upon it in the school library and was so impressed with it I wanted to nick it!

It's a very rare book and a couple of years ago the idea popped into my head that I would like to read it again but nobody had ever heard of it. Somehow, by fair means or foul, Tidyboiler managed to find a copy for me.

It's so well written with some great drawings that it's possible to learn to drive a Gresley Pacific class from it and that's how at the tender age of 18 I ended up driving this:

Engineer54 · Feb 13, 2014

GLENNSPARK said:
Engineer54 said:

Just shows you how long that service fuse has been in place. My parents house only had a 40A service fuse and a 40A meter for donkeys years. Then got updated out of the blue to 60A fuse and 100A meter. Later still, Mechanical meter replaced with digital meter and fuse/tails uprated to 80A/16mm....

Click to expand...

and it held for all that time....

which begs me to ask what the point in this excercise was?

No idea, no upgrades were ever asked for/requested. Not just my parants house, but the whole estate, street by street!! lol!! Talking about a period from 1952 through to 2005. It was around final year, they changed the meter for a digital one and upgraded the service fuse and the braided VIR 7/064 tails for 16mm....

GLENNSPARK · Feb 13, 2014

Engineer54 said:
No idea, no upgrades were ever asked for/requested. Not just my parants house, but the whole estate, street by street!! lol!! Talking about a period from 1952 through to 2005. It was around final year, they changed the meter for a digital one and upgraded the service fuse and the braided VIR 7/064 tails for 16mm....

it would have been interesting to have clamped the tails at full demand back then...

and again recently...

compare the results......

GLENNSPARK · Feb 13, 2014

Geordie Spark said:
I have that one and I have "2750 - Legend Of A Locomotive" which is a fictional story about an A3 Class Gresley Pacific named "Papyrus" that I've seen many times written by H.C. Webster. (I think I have some for diesel as well but let's not go there!)

I first stumbled upon it in the school library and was so impressed with it I wanted to nick it!

It's a very rare book and a couple of years ago the idea popped into my head that I would like to read it again but nobody had ever heard of it. Somehow, by fair means or foul, Tidyboiler managed to find a copy for me.

It's so well written with some great drawings that it's possible to learn to drive a Gresley Pacific class from it and that's how at the tender age of 18 I ended up driving this:

theres six of these in existance:

Mallard....a static display in the national railway museum York

Bittern...in steam at southall railway centre

Union of south africa...in steam at thornton yard

Dominion of canada...a static display at the canadian railway museum

Dwight D eisenhower...a static display at national rail museum green bay wisconsin

Sir nigel gresley...in steam at north york moors railway

Engineer54 · Feb 13, 2014

GLENNSPARK said:
it would have been interesting to have clamped the tails at full demand back then...

and again recently...

compare the results......

Well i can tell you that while Mum & Dad where living there, hob cooking was always Gas, as was heating and hot water, eg shower!! Though i did install a power shower pump in the latter years... lol!! So it was never really a high usage property, especially after my sister and myself had left the house