Earthing in Irish rural house.

[deiseboy]

Hi.
I live in rural Ireland with a supply via poles with what looks like 2 wires going from pole to pole. There seems to be a 3rd wire going into the ground at the base of the pole which I assume is an earthing point.
In the meter box, the earth and the neutral are joined together and there are 3 meter tails to the consumer unit giving a "normal" wiring set up with separate L, N and E for all the various circuits.
The consumer unit is an MK which I brought from the UK with all circuits protected by an 80 amp / 30 mA RCD Main Switch.

Q1. Is this what is described as a TN-C-S system? There's no label in the meter box.

Q2. Is any further connection necessary between the N and E inside the Consumer Unit or house?

Q.3 Any fault seems to trip the RCD. Could I alter the set up so that the individual MCBs trip instead?

Q4. Is there any way that we could have two electric showers and an electric cooker? The main supply fuse says 60/80 Amps.

Many thanks.

 

[solair]

There are a few issues here:

It sounds like a TN-C system if the earth and neutral are bonded together just before the meter at the ESB (power company) connection.

The other issue is that if the supply is currently de-energised (i.e. switched off). ESB Networks will require an official completion certificate certifying that your upgrade work is carried out according to ETCI (Electrotechnical Council of Ireland) wiring rules. Unless you're an electrical contractor registered in Ireland, you won't be able to produce on of these.
ESB Networks won't connect without one.

Also bare a few things in mind with your wiring:

1) ALL sockets have to be RCD protected in Ireland, there are no exceptions to this. This means for example, that the combined UK-style cooker switch+socket unit it illegal here.
Sockets are usually wired on 20A radials, not usually on ring circuits like the UK. Rings are permitted, but they're generally avoided. Normally, a 20Amp radial serves a group of near-by sockets. They're grouped into logical zones. E.g. half the kitchen, the living room, perhaps 2 bedrooms.

Only cooker and lighting circuits are exempt from RCD protection.

2) The consumer unit must have a main fuse, or specially approved master breaker that trips should the entire fuse board be overloaded. Even on modern installations, a "minized" switch-fuse is used as a fuse still provides ultimate safety in a fire as it will melt isolating the supply.

You can obtain a copy of the Irish wiring regulations from www.etci.ie (for purchase only)

You're more than likely going to need to get a local registered electrical contractor involved.

To answer your questions specifically :

The consumer unit is an MK which I brought from the UK with all circuits protected by an 80 amp / 30 mA RCD Main Switch.

Q1. Is this what is described as a TN-C-S system? There's no label in the meter box.

Contact ESB Networks for advice on this. It sounds like a TN-C connection.

Q2. Is any further connection necessary between the N and E inside the Consumer Unit or house?

No, and to do so is absolutely illegal here. Only ESB networks can make connections between neutral and earth, they call it "Neutralisation" here.

Q.3 Any fault seems to trip the RCD. Could I alter the set up so that the individual MCBs trip instead?

You could use combined RDC/MCB modules on each 20A circuit, but it is absolutely compulsory (since the late 70s) to have a 30mA MCB protecting any socket outlet, as well as water heaters, central heating systems etc. (The rules aren't quite so strict on this in the UK.)

If you are having regular trip faults, you should really resolve the faults rather than attempting to avoid tripping.

Q4. Is there any way that we could have two electric showers and an electric cooker? The main supply fuse says 60/80 Amps.

You can get a system of interlocks installed, this will ensure that only one shower is operated at a time. It uses a system of contactors (relays) on the circuit board which turn off the supply to one shower if the other is on.

Other than that, you would need to look at getting your supply upgraded to 100Amps. ESB can do this if the local system will support it, in a rural area that might mean upgrading a pole-top transformer and it can get expensive as it will be charged to you. But, there's no harm in asking!

Personally, if I were in a rural area and had space, I would look into non-electric options for heating showers. There are grants available for solar energy, heat pumps, etc and automated wood-chip boilers. So, if you combine them with electricity / gas and install a properly insulated water heater tank it can prove a LOT cheaper than using individual electric showers.

Check www.sei.ie (sustainable energy ireland) for info on grants.

Hope that's of some use to you!

 

[deiseboy]

Yes. many thanks for all that. I think I will have to get a local electrician in at least for advice and certification.