Earthing System in rural ireland

Umiq88

Can someone tell me what earthing system is used for houses in rural Ireland. I'm faliliar with the TN-C-S sytem and the TN-S system but I'm unsure of this house.

Its a single phase installation fed from a pole mounted trafo. An earth electrode is sunk outside the house and is connected to the main earth point which is also connected to the neutral point in the ESB/Meter box.

On a TN-S system the earth is distributed with the phase(s) and on a TN-C-S system the earth is split from the neutral at the connection point. What I have is similar to a TN-C-S system only the point at which the earth and neutral are seperated from the PEN conductor is connected to earth via an earth electrode. Because of this I'm led to think its a TT system but I'm not sure if this is used in Ireland and why is the earth connected to neutral at the meter box.

Do I have a TN-C-S-TT system

M cebee

it's tn-c-s anyhow by the sound of it

TT won't have any connection from the MET to the supply

Bruthal

psittacosis wrote: »

Can someone tell me what earthing system is used for houses in rural Ireland. I'm faliliar with the TN-C-S sytem and the TN-S system but I'm unsure of this house.

Its a single phase installation fed from a pole mounted trafo. An earth electrode is sunk outside the house and is connected to the main earth point which is also connected to the neutral point in the ESB/Meter box.

On a TN-S system the earth is distributed with the phase(s) and on a TN-C-S system the earth is split from the neutral at the connection point. What I have is similar to a TN-C-S system only the point at which the earth and neutral are seperated from the PEN conductor is connected to earth via an earth electrode. Because of this I'm led to think its a TT system but I'm not sure if this is used in Ireland and why is the earth connected to neutral at the meter box.

Do I have a TN-C-S-TT system

Sounds like you have a TN-C-S alright, Terra-Neutral-Combined-Seperate.
In a TN-S the neutral and earth are seperate from the supply transformer.

The earth bar in the house is connected to the neutral at the esb meter point, so this is where the neutral Seperates and goes to neutral bar and earth bar of DB. The neutral conductor between the Traffo and the metering point may have one or more earting points between the traffo and the meter point. In housing estates this would be done at the transformer and at mini pillars usually at front garden walls every few houses. In a single house fed from a pole traffo it would be done at the traffo pole, and at metering point.

So in your case the PEN is seperating at the meter point which is standard practice in TN-C-S systems, which is the main system used in ireland. But its at the esb`s discretion if its a TN-C-S or a TT used. Im not sure if TT is ever used now in a new installation or rewire, but there would be some houses still connected in this way.

M cebee

not now but it was common where i live anyhow

but it was pretty ropey

all supply types are common in the uk


a tn-c-s is commonly converted to TT for outbuilding sub-mains (in the uk)

Bruthal

M cebee wrote: »

a tn-c-s is commonly converted to TT for outbuilding sub-mains (in the uk)

How do they do this? L&N sub only out and then earth rod and RCD at outhouse?

M cebee

robbie7730 wrote: »

How do they do this? L&N sub only out and then earth rod and RCD at outhouse?

yes - 2-core swa glanded on supply side only (that protects the swa)


at outbuilding- all final circuits 30ma protected and a rod

think that's the just of it

RoundyMooney

It's TNCS alright.

However, please be aware that in rare cases, the LV earth (to use ESB terminology), ie. the earth on one of the LV connections on the transformer which creates the neutral, may in fact be that earth rod (actually generally a 5 rod earth or equivalent) in the ESB meter cabinet.

This is more likely where there is only one customer on said transformer, and the installation is older.

More likely that it is the customers own earth, but something to be aware of nonetheless.

M cebee

ya -they're common in older cabinets

a 6sq down to a rod in meter cabinet


are they are a DSO earth then

RoundyMooney

If they're 6 square, unlikely.

Any I've come across are generally bare copper.

LV earths are generally at the trafo, or on the first pole out (and on others, not necessarily all, for multiple consumers on the same LV group).

They would be DSO yes, but they predate any such terminology.

I'd advise anyone who comes across them to contact the local networks office, in most cases an earth can be run to the sub pole instead.

The danger being of course, if an unwitting person disconnects the only LV earth on the system, the reference to earth is gone, and the incoming voltage can float. The lights will still be on of course...

M cebee

it's common in older cabinets-a 6sq from the neutralizing point down to a rod

i always assumed it was an older method of connecting the consumers rod


maybe it was a 'rogue' contractor doing this:)

RoundyMooney

Maybe not rogue, but handier at the time than going back to the distribution board, as what you're describing seems like a customers earth to me, although it wouldn't pass muster these days.

What was common in housing schemes at one time was ten sq t+e ran out to the meter cab, but with the earth unused, and a separate earth (neutralising conductor) with it. Obviously the six square was considered too small.

This would be 70s era stuff.

John T Carroll

Bruthal wrote: »

Sounds like you have a TN-C-S alright, Terra-Neutral-Combined-Seperate.
In a TN-S the neutral and earth are seperate from the supply transformer.

The earth bar in the house is connected to the neutral at the esb meter point, so this is where the neutral Seperates and goes to neutral bar and earth bar of DB. The neutral conductor between the Traffo and the metering point may have one or more earting points between the traffo and the meter point. In housing estates this would be done at the transformer and at mini pillars usually at front garden walls every few houses. In a single house fed from a pole traffo it would be done at the traffo pole, and at metering point.

So in your case the PEN is seperating at the meter point which is standard practice in TN-C-S systems, which is the main system used in ireland. But its at the esb`s discretion if its a TN-C-S or a TT used. Im not sure if TT is everused now in a new installation or rewire, but there would be some houses still connected in this way.[/QUOTE


Some advise please on what type of Earthing System is in my house.

House built in 1970/71.

The Main ESB Fuse and Fuse Holder was renewed in 2007. It is a Henley Series 7 Type 2 a.

The ESB cable entry is at the bottom and the phase and neutral are taken from the top, into the Meter and onto the consumer fuseboard via a 40A/30ma RCD which was installed about 10 years ago and replaced the double pole (original) isolating switch.....all fairly normal I would think.

There are two (10 sq.mm ??) cables from the Main Earthing Terminal Box, one of these is inserted in the right hand side of the Fuse Holder about “1/2” way up between the ESB cable entry and the phase and neutral wires.......I assume its attached to the junction of my neutral and the ESB neutral. The other cable, (from the main earthing terminal box) goes straight down into my garage floor and I assume its attached to an Earthing Rod. I am absolutely sure that the Earthing Rod was there from the start as I was the only owner of the house, I cant remember the original ESB Fuse/Holder wiring set up but it may have exactly the same as it is now.

My query is, do I have a TN-C-S + TT “hybrid” system, and if so, why?? JTC

tomdempsey200

it's tn-c-s

but it's not normal to have an rcd main switch

John T Carroll

tomdempsey200 wrote: »

it's tn-c-s

but it's not normal to have an rcd main switch

Thanks Tom, the reason I asked is that any schematic/description that I've come across re the TN-C-S earthing does not show any earth rods on the consumer side but it does have multiple earthings of the PEN(ESB) line. Thats why I wondered was it a TT system originally. John

Stoner

John T Carroll,

I the interests of forum maintenance it is best to start a new thread on most issues unless we sticky it or there is a recent tread about the issue. Dragging up three year old threads can get a bit messy, thanks