Calling all Sparkies! Earthing System Type

[Gaijin]

Hi guys,

To cut a long story short, i'm looking at getting electric gates for the driveway and I will be getting in an Electrician to do the works.

However, this will be the first time I will be working with an electrician here and as such they will be a relative unknown to me despite any recommendations I may get.

As such, I am trying to educate myself as much as possible so that i am: A.) Happy that the proposed work is competent and safe B.) I don't get ripped off and C.) I'm actually interested (nosey)

So first things first, can anyone please confirm the earthing system I have from the picture below? Am I correct in thinking it's a TN-C-S?

 

[Gaijin]

Thanks guys for your comments.

It is an Irish property but my understanding is - like you say Beermonster - that the systems a very similar. I won't be taking anything for granted regs wise - it's more the electrical theory that I want to understand more.

I've done a little more reading on what both of you have mentioned regarding exporting the earth. Obviously i'm concerned about safety as in essence, the supply to the gates is theoretically going to be run from a consumer unit in the garage via an underground SWA cable to the IP65 metal control box which would be about 40 metres away.

So with that in mind, and from the reading i've done this morning, do I need to ensure that a secondary earth is used - such as an earthing rod or similar? I've seen a few different opinions on electricians forums - some suggesting to treat external runs such as this as a separate TT installation and earth the box and it's contents locally using a rod.

If the electrician were to use an earthing rod, would it best be used in combination with the supply earth or on it's own?

And would it be best situated near the control box or nearer the consumer unit end?

I've seen a suggestion to connect the earth of the SWA to the earth at the consumer unit end, but not at the other end, and then earth the control box and it's contents near the box itself TT style - does that make sense?

Thanks again for your help guys.

 

[Gaijin]

Also your meter tails are not double insulated and that cable going out from the bottom of the isolator/kmf looks awfully like 16mm twin - if it is your earth is likely undersized.

Thanks for highlighting this Lumeycom - I will point this out to him - What should be done about this in your opinion, and what are the current implications of this being how it is?

 

[Gaijin]

I've literally been reading all day about this and essentially all i've read is arguments between electricians. Essentially the regs are ambiguous if not a bit contradictory. There seems to be two camps:

1. Use supply earth, yes loss of neutral before the premises is potentially very dangerous, but incredibly unlikely - enough so as to not worry about.
2. Set up outbuildings etc. as TT and use localised earth electrode to bring down the risk, but with other potential issues.

The nightmare scenario I have is that if the unlikely happened and the control panel box became live - and then my son touched it.

Its a judgement call at the end of the day and factors will include:

How far away from the property are the gates
Is it concrete or just mud grass around the gates
Is there any other metalwork near by
How much metalwork is being connected to the earthing system, is it just a metal IP rated cabinet, or with the gate motors being 24v or whatever or does the whole gate end up being connected to earth

For clarity here's the answers to your questions:

1. How far away from the property are the gates? Approximately 40 metres SWA cable length from CU to proposed Control Panel
2. Is it concrete or just mud grass around the gates Where I've imagined the control box to be is in mud/grass, but right next to a kerb and tarmacadam
3. Is there any other metalwork near by? No, none really although i've flirted with the idea of running another SWA for garden lighting if a trench would be dug.
4. How much metalwork is being connected to the earthing system, is it just a metal IP rated cabinet, or with the gate motors being 24v or whatever or does the whole gate end up being connected to earth. The control panels i've been looking at (and the electrician may well change it) are metal IP65 painted in epoxy polyester paint (not sure if this provides any insulation). Gates would be 240V and the one i'm looking at has earth connections on the PCB so I imagine it would use the earth that the control panel uses.

 

[Gaijin]

Here's a crude diagram in MS paint:

If it's not clear, the control panel in my mind (again, electrician may see different) would sit halfway between the gatepost and the flowerbed you see just above the post box.

If it's not obvious, there is another (primary) consumer unit in the house near the back door.