Mains switch in Consumer Unit is only Single Pole

D

Deleted member 231978

TN-C-S in Ireland and in the US and in IEE recommendations uses local earth rods too.

It's a conservative approach to it and there are arguments in favour of it and against.
 
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TN-C-S in Ireland and in the US and in IEE recommendations uses local earth rods too.

It's a conservative approach to it and there are arguments in favour of it and against.

Thanks for the reply James - thats got me intrigued now. You couldnt point me in the right direction as to what the favour and against is about for that kind of system can you pretty please?
 
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All of this has been explained before (including the fact about the prosecution for illegal electrical works).

The purpose of an earth electrode is simply to provide an Earth reference for the ESB's PEN conductor to try to maintain it at Earth potential.

It is important to remember, however, that Restricted Electrical Works in the 26-Counties can only legally be carried out by a Registered Electrical Contractor. Anyone else doing this will be committing a criminal offence. Visit the RECI (Safe Electric) website to find a Registered Electrical Contractor.

For further information on Restricted Electrical Works visit http://www.walshelectrical.ie/electrical-services.html#restricted-works

For further information on Controlled Electrical Works visit http://www.walshelectrical.ie/electrical-services.html#controlled-works
 
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yes, yes I have got the message Risteard I myself must not, or get anyone not qualified, to do electrical work in Ireland - I am only discussing about it and saying that I would be interested in seeing why some people favour or again that type of earth system - in plain english and not having to wade through technical jargon's of the regulations. You cant blame me for being inquisitive - I understand that its illegal for anyone to mess around with electrics but I am still interested in it
 
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Deleted member 231978

I would reiterate the above : DO NOT MESS AROUND WITH EARTHING/GROUNDING SYSTEMS!

In general, in most countries in Europe and the US etc the local rules when applied correctly are extremely safe. Where you get accidents tends to be where someone has made an addition or modification to a system without understanding what they're doing and this is why many countries, including Ireland, restrict such work to Registered Electrical Contractors.

It is, however, useful to understand roughly how these things work as at least you can understand why things like equipotential bonding of pipework is so important. Or, how to recognise a neutral fault.

The main advantage of TN-C-S is that you ensure that it provides a solid, reliable earth and will trip MCBs or burn out fuses quickly in the event of a fault because the earth is likely to be at zero potential (O volts relative to the live).

It requires a well maintained, quite complex local distribution system, as the supply neutral must be earthed correctly regularly along its route back to the transformer. So, in some cases in remote locations it may be unsuitable as the overhead local distribution lines may not be capable of doing that.

TN-C-S also has risks where there's a neutral fault that can potentially cause currents to flow across plumbing systems or underground piping. If you ever notice live pipework always call a REC.

TT, where the consumer relies only on their own earth electrodes, has the advantage of being very simple, but you can't really ensure that the earth is reliable without regular testing. Electrodes can become damaged / corroded by soil conditions and so on. Also depending on the impedance of the ground, you can have issues with poor earths which can result in breakers not tripping in fault situations or even live bonded metal work. That's why you use an RCD across the whole system at a higher rating (fire protection primarily) and 30mA shock / human protection.

TT earthing systems are encountered sometimes in temporary installations - power for construction sites, caravans, etc etc and also in some remote areas where the network neutral is unsuitable for TN-C-S.

In some countries TT is also preferred and used as the normal approach. France for example.
This is why you will always see a "Disjoncteur" installed by the power company at the meter.

Again, this is another reason why if you're doing DIY work in another country, you need to understand how the local systems work. If you apply your own familiar approach to a foreign system, you can end up either creating serious hazards or exposing yourself to legal issues.

There's also a third type of earthing called IT, this is where the neutral point of the transformer is basically isolated from earth. It's used in specialist circumstances like operating theatres and mining where continuity of supply is essential. You will not encounter this in a home / office environment in Ireland or the UK.

You do, however, have widespread use of local isolation transformers for handheld power tools and shaver sockets. But, they're localised rather than 'systems'.
 
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Agree with all of that. There are also TN-S systems and TN-C systems. (These are not used in the 26-Counties, and indeed the use of a TN-C system is generally prohibited throughout all of Ireland.)
 
D

Deleted member 231978

I would add, if you think your house has wiring that's isn't up to scratch, just get an REC in to give it a once over. It's something you should always do when you move into a new house (or beforehand you buy, if you're doing a building inspection).
 
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I would reiterate the above : DO NOT MESS AROUND WITH EARTHING/GROUNDING SYSTEMS!

In general, in most countries in Europe and the US etc the local rules when applied correctly are extremely safe. Where you get accidents tends to be where someone has made an addition or modification to a system without understanding what they're doing and this is why many countries, including Ireland, restrict such work to Registered Electrical Contractors.

It is, however, useful to understand roughly how these things work as at least you can understand why things like equipotential bonding of pipework is so important. Or, how to recognise a neutral fault.

The main advantage of TN-C-S is that you ensure that it provides a solid, reliable earth and will trip MCBs or burn out fuses quickly in the event of a fault because the earth is likely to be at zero potential (O volts relative to the live).

It requires a well maintained, quite complex local distribution system, as the supply neutral must be earthed correctly regularly along its route back to the transformer. So, in some cases in remote locations it may be unsuitable as the overhead local distribution lines may not be capable of doing that.

TN-C-S also has risks where there's a neutral fault that can potentially cause currents to flow across plumbing systems or underground piping. If you ever notice live pipework always call a REC.

TT, where the consumer relies only on their own earth electrodes, has the advantage of being very simple, but you can't really ensure that the earth is reliable without regular testing. Electrodes can become damaged / corroded by soil conditions and so on. Also depending on the impedance of the ground, you can have issues with poor earths which can result in breakers not tripping in fault situations or even live bonded metal work. That's why you use an RCD across the whole system at a higher rating (fire protection primarily) and 30mA shock / human protection.

TT earthing systems are encountered sometimes in temporary installations - power for construction sites, caravans, etc etc and also in some remote areas where the network neutral is unsuitable for TN-C-S.

In some countries TT is also preferred and used as the normal approach. France for example.
This is why you will always see a "Disjoncteur" installed by the power company at the meter.

Again, this is another reason why if you're doing DIY work in another country, you need to understand how the local systems work. If you apply your own familiar approach to a foreign system, you can end up either creating serious hazards or exposing yourself to legal issues.

There's also a third type of earthing called IT, this is where the neutral point of the transformer is basically isolated from earth. It's used in specialist circumstances like operating theatres and mining where continuity of supply is essential. You will not encounter this in a home / office environment in Ireland or the UK.

You do, however, have widespread use of local isolation transformers for handheld power tools and shaver sockets. But, they're localised rather than 'systems'.

Thank you for the extensive reply - really appreciate it and get it now. - I looks like we have the TNCS system then at our house and a earth rod put in for extra protection, so one doesnt have to rely on other (IE if network earth system fails we still have earth rod system protection ... and if earth rod protection fails it still has network protection) am I right on that then? - so in fact the mains switch is single pole because its TNCS and by not isolating the neutral you keep the network earthing intact, have I got that right? - and if you were to have a DP mains switch on a TNCS it would break the earth as well as the neutral - alhough not on our particular set up because (if the earth rod is working as it is designed to it should still supply an earth to the household electrics even in a disconnection of neutral in the CU because the earth rod connects onto the earth bar of the CU as well as the earth wire going to the meter box's Neutral block. Have I that right?
 
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I would add, if you think your house has wiring that's isn't up to scratch, just get an REC in to give it a once over. It's something you should always do when you move into a new house (or beforehand you buy, if you're doing a building inspection).

if the house was wired up in 2007 (which it was, its written in the CU on a label) and the house was built around 2007 but the regulations changed/updated in 2008 would a RECI keep the wiring/consumer unit at 2007 regs or would they update it to the latest 2008> regulations? - in other words I havent read the 2007 (or pre 2008 RECI regs) but if say after the 2008 regulation it stated that the lighting circuit shall be protected by an RCD as well as the sockets or that the bathroom lights/shaver socket/heated mirror etc shall be fitted with an RCBO - then would the RECI engineer leave the CU at pre 2008 regs (say if at that time only requirement was sockets only to be protected by RCD) or would they suggest that the system has to be 'upgraded' to the latest regulations?
 
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I would add, if you think your house has wiring that's isn't up to scratch, just get an REC in to give it a once over. It's something you should always do when you move into a new house (or beforehand you buy, if you're doing a building inspection).
Absolutely. A Periodic Inspection Report is designed specifically for this purpose (although will likely be much more in depth than a simple once over).
 
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So, we didnt actually get around to answering the question about if a RECI installer checked the premises which was wired up before 2008> regulations - would they base the installation on pre 2008 regulation or would they say it has to be up to date regulations? i.e. if before 2008 regs it said only the socket circuit shall have an RCD in the CU but after 2008 the regs require a RCD on the lighting circuit as well ... or RCBO on the bathroom lighting circuit in the CU would the RECI electrician condemn the installation because it does not comply to up to date electrical regs or would he say "no thats OK because when your house was built and the CU was put in that was the regs at the time" ?
 
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So, we didnt actually get around to answering the question about if a RECI installer checked the premises which was wired up before 2008> regulations - would they base the installation on pre 2008 regulation or would they say it has to be up to date regulations? i.e. if before 2008 regs it said only the socket circuit shall have an RCD in the CU but after 2008 the regs require a RCD on the lighting circuit as well ... or RCBO on the bathroom lighting circuit in the CU would the RECI electrician condemn the installation because it does not comply to up to date electrical regs or would he say "no thats OK because when your house was built and the CU was put in that was the regs at the time" ?
A Periodic Inspection would assess the installation against the Wiring Rules, but bearing in mind that non-compliances which were allowable at the time (e.g. distribution board above maximum height) might not require remedial work. Lack of RCD protection to socket outlets, however, would be considered a very serious non-compliance.

If serious defects were identified which could not be rectified at the time then you are liable to receive and be made to sign a "Notice of Potential Hazard".
 
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