Please help me understand my new house electrics

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Hello,

Not been on here for a few years. This place was a great help during my renovation including full DIY rewire. That all went fine in the end - notified, did all work myself including inspection and testing, submitted EIC and got my completion cert (and added to some council approved electricians who don't belong to a scheme list, which was nice).

Anyway - that place is now sold and I live in Norway. Been renting apartments for three years whilst saving, and now have bought a house and just moved in last week. There's some extremely knowledgeable folks on here, and I'd be interested in some feedback/opinions on my place's electrics - safety and just generally what the heck is it?

One thing I notice in practically every property I've been to over here is unearthed sockets are everywhere, and my place is the same. Makes me feel concerned. It mightn't be so bad by itself, but couple that with the fact the country uses almost entirely electric heating, you commonly see class 1 metal cased panel heaters plugged into these unearthed sockets. Plus computers, freezers, etc. Only kitchens and bathrooms usually have earthed sockets.

What I'm wondering is, is there something inherently safer and less concerning about that situation over here by account of the network or the buildings? I.e. the buildings are almost entirely wood which I guess is reasonably insulating. My house has a concrete basement level though. Very new builds tend to have earthed throughout, but unearthed sockets can still be purchased from the local DIY shed.

I read that the network is mostly actually IT (something to do with the ground being all rock and not being able to get reliable earth connections or something) with only new build stuff now TN C S. Not yet sure what mine is though or how to reliably find out. Now I know how IT is from a diagram, but I don't fully understand the physics of how it would behave, specifically with regards to touching a phase live due to a fault/accident whilst standing on my wood floor.

I mean does IT mean it's fundamentally safer for me to touch live while standing on earth as there is no low impedance path back to the transformer to complete the circuit, or am I not getting it?

I measure about 120 - 130 V between live and my house's earth or between neutral and earth. Is that some indication or proof the network is IT? Surely those figures wouldn't be possible on a TN network? Again I'm not sure about that.

At least the cabling seems to have earth present (except for lighting I think), so should I be running round replacing all sockets with earthed ones so I sleep better at night? If the network is really IT, what does a consumer protective earth actually do? I mean a live to earth fault wont neccessarily pull enough current to trip an MCB, right? So might just leave a metal case at live voltage even if earthed, or am I talking crap? Would trip an RCD though, I guess, which I dont have :/

The next funny thing is I have a three phase supply. Well I initially thought I did, but now I have a different theory. Here's some terrible pictures of the CU - sorry I'm not sure what box the real camera is in...

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At least it's spacious :). Nice mix of brown and blue, or just use black for everything if they fancied it. The incommer is the three wires (black brown and off-white) and I think the main earth lead wrapped in green and yellow tape (but I cant see if that is actually within the incomming service or seperate. So if that is three phases, where is my nuetral? I'm therefore thinking maybe I actually have two phases and neutral? Is that even a thing? The only thing I have found so far that uses more than one phase is the cooker hob, but I'm pretty certain that is 400V single phase as it clearly is wired with two phases and earth. Meter is three phase and the three incomming wires all go through the meter (but neutral does anyway in single phase). Could it really be two phase and neutral?

I guess I need to pop off some panels and have a better look and maybe take some measurements to confirm.

That lone RCD is the other odd thing in my opinion. It is the feed to part of the basement that was built as a standalone apartment with its own CU, so it can be rented out seperately and have a separate electric bill (although the previous owners never used it as such and there is no separate meter, but one could be added I guess?). Surely it's stupid to have the RCD in the main house CU? If I do rent the basement apartment out (we intend to) and if I ever go away and the tennant does something to trip the RCD, they are screwed till i get back, right? Surely I want the RCD in the basement CU and just a switch in the main CU (or nothing - just a henley type of thing to directly feed the basement)? Nice that they decided to RCD protect the tenants, but not the main house.

OK this is long enough already. Thanks for your time anybody who made it this far. Any opinions appreciated.

EDIT: Ah that shows how long since I've been here - I completely forgot there is a whole different forum for electrics outside UK that I suppose this ought to be in :oops: . Mods please move if you like. On the other hand, it might get read in here :)
 
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IT in the UK is very limited only really used with the bathroom shaver socket. I have only worked with IT once on a tunnel boring machine in Hong Kong and clearly with an IT system there is no point in having an earth as such.

Are you sure it is IT and not TT or American hot wire system?

Since supplied from a delta wound transformer earth is not an option I note all MCB's are twin pole.

The Americans have an odd system where they have a centre tap on one of the transformer windings as to if copied else where I don't know.

But this is a UK forum and to get advice about a foreign system you really do need to ask people with experience on that system.

Looking up Norway it says the "Type C" Europlug and the "Type E" and "Type F" Schuko are used this does not seem to fit with an IT system are you sure it's IT and not TT?
 
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Woo a reply :). Thanks! Man I thought everybody would be up for stimulating discussion on the intricacies of different network types. No??? :)

I'm really not sure to be honest. It's a couple of sources I read they are strange and use IT over here. Probably Wikipedia quality of sources though.

I've seen diagrams on some techy places of IT networks and they show it as star connected as 'normal' just with no connection of the star point to earth at the supply, or a high impedence connection. Protective local earth for consumers was shown. I think it must be star connected as I have 220/380 V available.

I haven't read anything that suggests they use an American style system, but not sure. TT sounds like a possibility but again not sure. Would my live to earth and neutral to earth readings be possible on TT?

The two pole MCBs - is that just a general Euro thing as they don't tend to observe polarity and therefore always disconnect phase and neutral? Or is that not found in the rest of Europe and might be specific to here and indicative of something else?

So I need to do some more investigation. I can confirm if I have two phase and neutral or three phase easily enough, but I think it must be the former. I am reminded that the EIC form has an option for two phase three wire, so it must be a thing!

I guess I already know the answer regarding the RCD - stupid place and it should be moved to the apartment CU, right?

Still not 100% if I should run around replacing sockets for earthed ones, but I guess if they typically do have them in potential wet locations, it implies they do reduce risk as per everywhere else in the world and there are probably no nuances of whatever funny network they have here that could mean it actually increases risk, so on balance it probably cant hurt.

I guess I could also consider replacing all the MCBs with RCBOs if I'm really concerned.
 
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Can you install some sort of rudimentary earth rod and test to see if you get any reading at all?

The readings you are getting now are consistent with what we see here on a circuit which has lost it's earth. Certainly not a safe situation.

I know nothing of local ways but physics don't really change between countries. If you can get a reading off a rod, I'd definately TT the supply.
 
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Hmmm good point RF - thanks. I ought to be able to find a metal spike somewhere. It's a shame I don't have the nice MFT I used in the UK over here, though.
 
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I'm getting a bit confused here. If the supply (transformer) really is not earth-referenced (which I find rather hard to believe), as BAS has implied, I can see no point in connecting the installation to true earth - since, AFAICS, that would not achieve anything useful I can think of.

In such a situation, one could presumably only have 'fault protection' (protection against 'live' exposed-conductive-parts) if CPCs of the installation were connected to the supply neutral - which would certainly not be allowed in UK. Mind you, if the supply really were 'floating', I suppose that the need for fault protection would perhaps be debatable.

Kind REgards, John
 
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I'm getting a bit confused here. If the supply (transformer) really is not earth-referenced (which I find rather hard to believe), as BAS has implied, I can see no point in connecting the installation to true earth
The point of an earth in an IT system is to limit the touch potential in the event of a first fault with anything outside the equipotential zone, hence the requirements in the BGB. The closer to true earth you get the lower the voltage of the exposed metalwork under that first fault condition. Without an earth all IT installations where ADS is used as the protective measure would be potentially unsafe.

Clearly the first fault condition cannot be allowed to continue without some sort of detection. In industry where installations are under supervision this would be a device which continually measures the insulation of the line conductors to earth and provides a warning of some sort, allowing the installation to function as usual until the fault can be fixed. In peoples homes, this would not be allowed, and so an RCD would be installed to trip out the circuit straight (which is what makes IT so pointless in domestic installations) with a high-impedance earth connection on one of the lines.

If a second fault were to occur, i.e. a second line connected to earth, then effectively you would create a short circuit between the two lines, and the fault would be cleared by the normal circuit protection.

The only way to effectively test you circuit is to test the earth and then prove its effectiveness by applying a first fault. What you should see is the voltage not rising to dangerous levels, and the RCD should also trip. That's if you really do have an IT installation of course!
 
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if CPCs of the installation were connected to the supply neutral - which would certainly not be allowed in UK.

:?: :?:

Isn't connecting CPC to Neutral the way PME in it various forms creates the "earth" for the system ?

I find it hard to believe that any domestic supply network would not be earth referenced.

It would be "safer" without an earth reference in that touching a live wire while standing barefoot on wet ground would not complete any circuit and hence little if any current would flow through the person and any RCD if fitted would not trip.

But if two people did it and each was touching a different phase then a circuit would be completed and current would flow through the bodies

Phase A---body A----ground----body B----Phase B

Or it could be

Phase A---body A----CPC----body B----Phase B

again there would be no un-balance to trip an RCD if it were fitted
 
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The point of an earth in an IT system is to limit the touch potential in the event of a first fault with anything outside the equipotential zone, hence the requirements in the BGB.
I don't really get it. If the supply really is truly floating, then no current from L can flow through anything (including human beings) other than via the supply's neutral return path, so that 'touch voltages' seem pretty irrelevant. For obvious reasons, L-N shocks are undetectable by any sort of device.
The closer to true earth you get the lower the voltage of the exposed metalwork under that first fault condition. Without an earth all IT installations where ADS is used as the protective measure would be potentially unsafe.
As I said,if the supply is totally floating, then ADS (whether achieved with OPDs or RCDs) cannot work unless CPCs are connected to neutral within the installation - which, as I said, would not be allowed in the UK.

Kind Regards, John
 
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if CPCs of the installation were connected to the supply neutral - which would certainly not be allowed in UK.
:?: :?: Isn't connecting CPC to Neutral the way PME in it various forms creates the "earth" for the system ?
Yes - but, at least in the UK, TN-C-S is only allowed when provided by the supplier - one is not allowed to establish one's own CPC/neutral connection within the installation.
I find it hard to believe that any domestic supply network would not be earth referenced.
As I said, so do I. However, my comments related to the situation (as suggested) in which the network is NOT earth referenced.
It would be "safer" without an earth reference in that touching a live wire while standing barefoot on wet ground would not complete any circuit and hence little if any current would flow through the person and any RCD if fitted would not trip. ... But if two people did it and each was touching a different phase then a circuit would be completed and current would flow through the bodies
Sure - but nothing can protect people against phase-phase shocks, any more than it can protect them from L-N shocks - since the 'shock current' is indistinguishable from current travelling through a legitimate load. [I'm assuming that in a multiphase installation such as the OP has, there will be CPCs connected exposed-c-ps, even if those CPCs are not connected to earth. That being the case, in the extremely unlikely scenario of two difference phases developing simultaneous faults to difference exposed-c-ps (which seems to be what you are postulating), an OPD would then operate.]

Kind Regards, John
 
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I have worked with one IT system it was a real pain. I will admit I often use earth as a reference point for meter that does not work with an IT system you have to find two lives.

Day to day different parts would end up being earthed so the idea of a earth fault blowing a fuse just didn't work yes still bonded so touching two bits of exposed metal work did not result in a belt but no point is earth rods just nothing to connect it to.

I don't think it will be an IT system. There seems to be loads of earth wires.

I have worked with some odd systems and what one finds is the local community knows what they can and can't do if they are to avoid shocks. When in Turkey I realised if the same system had been used in UK there would be deaths galore but the locals realised the danger and avoided it.

It's only when we work with the British if it's dangerous they will not allow it attitude that we get problems.

We of course do the same with some things I am sure today if some one invented the gas hob it would be banned as unsafe. As a child we had open fires and I was told "Hot it will burn" I am sure I made some errors but I learnt not to play with it. However take my grandchildren to a house with an open fire and they have no idea of the dangers so much more likely to be injured.

There is a saying about "When in Rome" and I think you need to adapt. If you make your house super safe like a British one then when you children leave the home they will have no idea of the dangers.
 
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I don't think it will be an IT system. There seems to be loads of earth wires.
As I keep saying, I do think it's very unlikely that the supply is not earth-referenced. In fact, what has been described is not really an IT system, but more like an 'II' one (neither supply nor installation earthed) - and I've never heard of such an arrangement as that.

As you say, there are certainly lots of G/Y cables, presumably CPCs connected to exposed-conductive parts - but that does not guarantee that they other connected to anything other than exposed-c-ps (and each other).

Kind Regards, John
 
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I don't really get it. If the supply really is truly floating, then no current from L can flow through anything (including human beings) other than via the supply's neutral return path, so that 'touch voltages' seem pretty irrelevant. For obvious reasons, L-N shocks are undetectable by any sort of device.
What neutral? :D Agreed I agree it sounds a bit silly, but if you have long circuits then capacitance will play a role and so the first fault may cause problems.

As I said,if the supply is totally floating, then ADS (whether achieved with OPDs or RCDs) cannot work unless CPCs are connected to neutral within the installation - which, as I said, would not be allowed in the UK.
I agree, hence the high impedance earth mentioned in 7671 to permit the RCD to work in domestic situations. It's still ADS as you have exposed metalwork and a cpc or cpcs acting as the current path under second fault conditions. Put it all in plastic and it will be Class II, so no cpc required.
 
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I don't really get it. If the supply really is truly floating, then no current from L can flow through anything (including human beings) other than via the supply's neutral return path, so that 'touch voltages' seem pretty irrelevant. For obvious reasons, L-N shocks are undetectable by any sort of device.
What neutral? :D
True, if it's a 3-phase supply, then there might not be a neutral. I should have said "the other live conductor(s)", rather than neutral! However, my point remains.
Agreed I agree it sounds a bit silly, but if you have long circuits then capacitance will play a role and so the first fault may cause problems.
That again :) You're not going to get enough capacitance in a domestic installation to do anyone any harm!
As I said,if the supply is totally floating, then ADS (whether achieved with OPDs or RCDs) cannot work unless CPCs are connected to neutral within the installation - which, as I said, would not be allowed in the UK.
I agree, hence the high impedance earth mentioned in 7671 to permit the RCD to work in domestic situations. It's still ADS as you have exposed metalwork and a cpc or cpcs acting as the current path under second fault conditions.
Adding a high impedance path to earth from the neutral of an otherwise floating supply certainly allows an RCD to operate in response to the 'first fault' - but if that's the only fault, I'm not sure that I see the point/need. As for the 'second fault', I'm not sure what you/they have in mind. As I've said, provided the exposed-c-ps are all connected via CPCs (even if the CPCs aren't connected to earth or anything else), if faults from two different live conductors to exposed-c-ps arise, then an OPD will provide ADS, won't it?

Kind Regards, John
 

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