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TNC installation - Continental Europe

vantech
  1. Hi,

I am looking at re-wiring a small apartment on the continent. The supply to the building is a TNC.

I was quite surprised to find a 4 core 6mm cable coming into the building from an underground cable, with the 3 phases landing into 80A fuses and the neutrals twisted together with an aged bit of tape around them. There are then multiple 4mm cables that connect to the secondary side of these fuses, which go off to the various properties.

The properties themselves have a consumer DB, with the phase conductor landing in a 32A MCB. The neutral then lands into the neutral bar, with a link to the earth bar.

I just wanted to clarify the following. 

Q1: 

When upgrading this apartment, I obviously want to use RCDs. I believe in order to do this, I would need to land the incoming neutral into a suitable connector, which then links to the neural terminal of the RCD and also the earth bar - this would then give me a TNC-S earth and neutral. The neutral output of the RCD is then in essence measured and compared to the phase conductor for subsequent outgoing circuit protection. 

Q2: 

I am assuming that the supply authority rely solely on the consumers “main switch” which is in essence an MCB to ensure the cable between the suppliers main feed and the property isn’t overloaded, because the suppliers fuses are not rated to protect the 4mm cable that comes into the property. I believe they have rated the fuses high enough to cope with the maximum demand for the connected properties. 

This would then mean, that the phase conductor needs to land into this MCB before the RCD. Is a single pole MCB really the best choice, or should I look to use a double pole MCB that disconnects the phase and the neutral conductor, and if so, what then happens to the earth?  

Obviously all of this falls outside of BS7671, because this standard doesn’t apply on the continent. I am just looking to clarify my understanding. I have actually looked at various installations and all of them are the same. The standard of wiring and associated safety devices/methods doesn’t even compare to what we do in the UK.  

I have also looked at using a local electrician - really not an option considering the state of some of the installations I’ve seen! 

Thanks. 

  • 0

    Your metallic water mains and stopcock are in a locked cupboard, you are then running the water in plastic, why not have another stopcock on the plastic pipe for maintenance outside the the cupboard?

    Also why tiles throughout? Laminate flooring is also nice.

  • 0 in reply to OlympusMons

    Yeah we will do this, plastic on the inside. There is literally a kitchen area and bathroom. The stopcock will go next to the boiler. 

    Tiles will be everywhere - unfortunately I won’t be able to convince the other half to go for anything else, just for the sake of better protection from grounding ;-) 

    Thanks. 

  • 0

    Tiles will be everywhere

    It might be worth a test or two - I suspect dry or glazed ties will be reasonable insulators (I'm thinking of the old the porcelain connector blocks..)

       - Andy.

  • 0

    the use of a PEN fault device can only add to the safety of the system I believe.

    As with everything there will be cons as well as pros, so see how one balances against the other. Some of the cons with device is that you're making the earth connection to the installation less reliable - mechanical moving parts, extra joints, possibly some contacts welding closed while others open, and so on - all far less reliable than a single bolted joint. If you do loose earth you've additional risks not only from loss of ADS, but a much greater risk of shock due to normal protective conductor currents making exposed metalwork live. In the UK risks from broken PEN conductors are usually considered negligible inside buildings - and we have our share of concrete structures and solid floors and we're hardly immune from broken PEN faults (I think they're currently averaging at about one a day across the UK)

       - Andy.

  • 0 in reply to AJJewsbury

    Yeah I think they’ll offer reasonable insulation, however for the sake of £200 for a matt:e, disconnecting the entire supply when the voltage goes out of limit does seem like the easiest and most robust solution available.

    I’m sure the spec of the tile will change 100 times before they are laid ;-) 

  • 0 in reply to mapj1

    Mmmm….. Thanks Mike. I’ll take a better look at that when I’m back in the office on Monday Slight smile

  • 0 in reply to mapj1

    Hi Mike

    Yes it's because the author's profile has been deleted which means any content they'd also personally uploaded into and linked from their file storage area (images/videos etc) has also been removed.  

    I can see some images in the thread such as the one in the OP (although it seems to depend on which browser I'm using) as well as one in a reply of yours that starts with "Well it is not that clear which cores are lives and neutral/earth in the supply or the loop supply..."

    I think any images that were embedded within the thread posts itself are still there but as the OP had posted links to images within their personal file storage, they're no longer available after they deleted their account.

    Hope that helps?

    Lisa

  • 0 in reply to Lisa Miles

    Thanks Lisa,

    ah, well at least we know what has happened - it is quite a limitation that the text of the posts remains but the images those words describe do not, but  I can now see why that is.

    regards

    Mike

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