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I'm not at all an expert in electrical engineering so I'll try to do my best of explaining my issue.

I live in Finland and I own an apartment that was built in the 80's. There has been some renovations done and the kitchen and the bathroom have been updated with grounded plugs as per regulations. Nowadays grounding is done with the 3 wire system where the ground is it's own separate wire, but for old building like this that do not have a separate wire for grounding, it is allowed to do the grounding per plug basis by combining neutral/ground which I think is called TN-C-S network. Until the building management agrees to upgrade the building's grid to 3 wire system, this is my only option.

I would like to update plugs in other rooms to be grounded as well to get rid of any possible noise and give the possibility of using surge protectors as they require grounded plugs or even better, get surge protection on the grid itself if possible.

  1. Is there any benefit of using a system of combining neutral/ground at the switchboard (behind a residual current circuit breaker there) and bringing the wire from there to the plugs as opposed to combining the neutral/ground behind each individual plug?
  2. Are there any other ways I could make sure my electrical equipment is protected from noise or power surges other than buying external equipment like UPS?

In my old apartment, that had a very outdated electrical grid with no grounded plugs, I experienced some sort of noise or power surges that caused issues with my PC and router causing them to randomly restart or drop internet connection. One time one of the PC's power supplies died because of a thunderstorm. I would like to get the best protection possible from those kinds of issues and would prefer to do as much upgrade as possible to the apartment's grid itself not having to mostly rely on external devices.

Edit. To add, the current switchboard is old, from the time the building was built so it has no residual current circuit breakers etc.

Edit 2. I had electrician come over and plan the renovation, but the way he dismissed my worries made me want to look for second opinion.

Essentially, as far as I understand or how he made it sound, only way to get grounding is connecting neutral to ground and this can be either done at the switchboard and delivered from there to the outlets or on each individual outlet just connecting those two behind each of them to make them grounded.

I've read about the dangers of this kind of setup and I was under assumption that doing it the switchboard way is safer. Is this true? The electrician said there's no difference and doing it the switchboard way is just extra work for no gain.

I found an image to illustrate the difference in which the setup on the left is what I want and setup on the right is what the electrician recommends to do instead.

enter image description here

Edit by Harper: This drawing neglected something critical. I added it in red: actual system grounding.

Update: I'm not sure what the image I posted was missing, but as I said, I have no knowledge about electrical engineering. To recap: The circuit breaker panel in the apartment does not get a separate grounding wire. Only wires there are neutral and live. If there's any grounding at any point, it would be at the building's power center. I am not allowed to do any modifications to the wires from the power center to my apartment.

Looking at the comments and after talking more with the electrician, it seems that it is indeed best to do the wiring at the panel instead of at each individual outlet. The panel will be replaced with a new one and all the circuits in the panel will be protected with RCD's. Obviously the best option would be to have all three wires completely separated (TN-S), but until the building's grid is upgraded, there's nothing else I can do. At least the apartment will be ready for future (hopefully) upgrade of the building's grid. The electrician clarified that the current grid in the apartment is TN-C and after this renovation it will be TN-C-S. Thank you all for your replies.

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  • 3
    This is one of those questions where you will need to ask a suitably qualified and experienced electrician to visit you. A good electrician will inspect and (where appropriate) perform measurements on your existing system and make recommendations based on facts rather than random guesses which is all you'll get from random strangers on the internet. Jul 9 at 14:03
  • Thank you. That link was really useful. As for electrician, I had one come and plan the renovation, but he didn't seem to understand as to why I'd want the plugs to be grounded questioning any benefit I'd gain from it. I wanted to get a second opinion from someone else. Jul 9 at 14:49
  • Your illustration makes it appear to be a trivial difference. That's super wrong, and unfortunately that is how morons see it when they look inside a properly done panel. The illustration also left out an important part. Jul 13 at 14:55
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Your situation

I'm most familiar with the US, and will be describing some things using the specific terms used by the US electrical code (except I will be calling the neutral wire neutral, since to use the phase the code uses would only cause a lot of unneeded confusion). You can read about what these terms mean below in the background section, which explains the US system, and describes the basic concepts in play.

The system the US uses is classified as TN-C-S, although that term can refer to any system where ground and neutral are sometimes combined ("C") and other times separate ("S"). If at the consumer end, the wires are combined, then for our analysis, the parts where it was ever separated don't matter, and the whole thing would be a TN-C system.

I'm not completely certain what you mean by "grounding on a per plug basis". If you mean you connect the neutral pin and the ground pin of your electrical outlets to the same wire then you are a "TN-C" system. I'm assuming this assumption is correct for the rest of this analysis.

Separating out the equipment grounding conductor and neutral within your dwelling, but connected together only at your circuit breaker panel would absolutely have the potential to provide safety benefits for certain types of fault (most specifically, it would mean a broken neutral wire that comes after your circuit breaker panel ​would not electrify exposed metal). It would also reduce the amount of of electrical noise on the ground pin.

Combined with Human protection rated RCD/GFCI equipment that provides very good safety protection. Warning: the RCD term often refers to devices designed only for fire protection (~30mA), not human protection (~5mA, although apparent ~10 mA for this is common in Europe, which should also be fine). Ideally you want the 5-10mA level protection on all circuits, but 5mA is typically too low a current to allow for one device for the whole house, due to nuisance tripping concerns.

It would not quite provide all noise resistance of the basic US grounding system even if your neutral gets connected to the earth somewhere in your building. The missing bit is that ideally the path from the ground pin to the earth should ideally never travel along any conductor that normally caries current. This is basically true in the US system, although we are not super strict about it in that at the main breaker panel we often freely intermix the neutrals and equipment grounding conductors on a single busbar rather than separating them into two bus bars that get connected.

But adding additional paths to the earth can actually have negative safety or noise implications in some scenarios, so I would not propose doing anything there without the signoff of an electrician who not only knows the rules very well, but also understands why you would want to go from TN-C to TN-C-S.

As for legality of any modification, I certainly know nothing about the rules over in Finland.

Background

Let describe how the electrical system works in the US, as it allows me to explain the system I am most familiar with, and introduce some concepts that are potentially relevant.

In the US from the transformer to you house runs 3 conductors: Two live conductors, and one neutral one (For comparison with your system, it is fine to mentally combine the two lives into a single one, the two are simply how we ensure access to both 120v while retaining access to 240V for high power devices). The neutral wire is grounded at the transformer. However, the US electrical system mostly does not rely on that connection for safety.

Instead, wherever the service disconnect switch is located, the the wire system becomes a 4 conductor system. The service disconnect is typically in the main circuit breaker panel (literally the main circuit breaker itself), but sometimes earlier like when the electric meter has an integrated main breaker, or it could theoretically be a non-breaker switch.

This fourth conductor is typically a wire called the "Equipment grounding conductor", however if certain types of metal conduit are used, the conduit itself can be treated as the equipment grounding conductor. In either case, the ground pin of the outlets get connected to this equipment grounding conductor and metal appliances connect their metal exterior to the outlet ground pin.

At the service disconnect, the equipment grounding conductor gets physically connected to a wire ("grounding electrode conductor") run to a metal stake ("grounding electrode") connected to the earth itself, and is also connected to the neutral. There are several intertwined ideas going on here.

The connecting of all exposed metal together via the "equipment grounding conductor" is called bonding (technically bonding just means connecting two pieces of metal together, but in electrical systems when used as a stand alone term it often specifically refers to connected exposed metal together). By itself this form of bonding does nothing really useful, but it is an important part of the following two concepts.

Connecting the bonded exposed parts to ground is called "grounding" or "earthing", and this form of grounding is primarily for dissipating static electricity.

Connecting the bonded exposed metal to the neutral has does not have a distinctive name, and is often called "bonding" or "equipment grounding". The idea here is that if exposed metal (which we previously bonded together and grounded) were to become electrified, due to some fault causing it to be in contact with a live conductor, we want there to be a low resistance path back to the source (transformer), in order that the circuit breaker will trip, causing the metal to no longer be electrified.

The earth itself is a pretty high resistance, high enough that it won't let enough power flow to trip the breaker, but unfortunately often low enough resistance that lethal amounts of current can potentially (in the wrong circumstances) flow through a person, into the earth, and back to neutral via the earth. When water is involved, even non-lethal levels of current can be deadly, due to it paralyzing you, and then you can drown. Hence why exposed metal being electrified needs to be automatically identified and stopped via blowing the circuit breaker, tripping an RCD/GFCI or similar.

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  • Thank you for the thorough explanation. By "grounding on a per plug basis" I think I meant exactly what you described which is connecting neutral and ground at the electrical outlet instead of at the switchboard. I had an electrician come over and he questioned as to what benefit there would be to gain to completely rewire the outlets instead of doing that connection on each individual outlet. He said "what's the point of doing connection at the switchboard and getting the wires from there to the plugs instead of doing the connection for each plug for way less work". Jul 10 at 11:33
  • I added an image to my post to illustrate the differences. Jul 10 at 12:01
  • 'Until the building management agrees to upgrade the building' you're SoL because "the path from the ground pin to the earth should ideally never travel along any conductor that normally caries current." (which includes neutral wires) +1. Especially if you're not willing to 'rely on external devices' to clean your dirty power. 'Grounded' receptacles are nice but they're tertiary to the reliability of your provider and the building's power scheme. The only thing that will reliably protect it from over and under voltage, is your #2 : a battery backup system.
    – Mazura
    Jul 10 at 21:58
  • Given the current status of of ground pins connected directly to the neutral at the outlet, moving the connection to be at the panel is an indisputable improvement in safety, and ought to help at least somewhat with noise on the ground pin. They proposed a connection behind the (presumably fire-rated) RCD. That provides more advantages in safety, as it means the RCD will notice any significant leakage to the ground pin. Lastly it also makes the the internal wiring of the dwelling ready for if/when landlord upgrades the building. Jul 13 at 14:14
  • Note that as Mazura alludes to, this won't help meaningfully with noise on the other lines like live. If you have issues with that, it would need a very different solution. Jul 13 at 14:17
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Depends what you're after.

Equipment protection

If you want equipment protection from ESD and the like, then "bootleg ground from the neutral" will suffice. It's a disaster from a safety perspective, though.

Human life safety

For life safety, bootlegging ground off neutral is very bad news. An ordinary break or weak connection on the neutral wire will result in the chassis of the equipment becoming electrified.

However, this can be cured using a voltage differential device, aka "ground fault detector" aka "Residual Current Detector".

To be useful for human safety, it needs to be in the 5 milliamp range. Most RCDs in Europe are in the 30ma range - intended more for H-G or N-G parallel arc fault detection in older wires. The higher (more tolerant) 30ma threshold allows them to be used to protect a whole house without frequent nuisance trips.

Americans are notorious for using 5ma RCD on a per circuit or even per outlet basis. This allows the sensitive detection threshold without nuisance trips, and localizes the trip to the thing causing it.

That is exactly what would work the best here.

Note that it's important for the ground to bypass the RCD - don't bootleg it off neutral on the protected side of the RCD, or the RCD will not be able to distinguish hot-ground faults from normal power draw.

That drawing is very defective

The drawing, as drawn, is very misleading, because they disregard what the neutral-ground bond is even for.

enter image description here

While I was in there, I also drew where the breaker is (in green) and where the RCD ought to be placed (in blue). Notice how ground bypasses the RCD.

Here's what's really supposed to be happening.

enter image description here

So that makes a lot more sense, doesn't it? Earth actually goes to earth and that is the main point of having the third wire.

And these two things are not equivalent at all!

So what's the deal with that (pink) bond that they were pretending is equivalent to a bootleg? It does two things.

  • If hots and neutral were totally isolated from ground, they could "float" at any voltage relative to ground. This equipotential bond spikes the neutral to near earth, so the hots are also within 230V of earth.
  • It creates an easy path for ground-fault current to return to neutral, so high current will flow and trip the (over-current) breaker.

This also helps RCDs do their job; as it makes it easier for fault current to bypass the RCD and cause a detectable imbalance. See how it would be catastrophically bad to bootleg ground downline of an RCD?

Lastly, fire your electrician, he is a moron who places low value on human life, and is fond of looking at data wrongly in order to rationalize anything he wants.

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  • Europeans use 10mA RCDs (either socket-outlet or breaker type) as their equivalent of N. American Class A (4-6mA) GFCI protection Jul 9 at 23:43
  • Given a choice between connecting the ground pins to the neutral at the outlet, vs at the panel, at the panel is clearly a better option, since it means any broken neutral that occurs after the panel not a safety issue anymore. It obviously won't help with a broken neutral that occurs before the the panel, but that would wiring outside of the poster's control. Getting a grounding electrode installed at service entrance and bonded to neutral there, and a separate EGC run to OP's panel to connect to instead of neutral would be best, but that sounds like it is on the landlord to do. Jul 13 at 15:16
  • Than you for your comment. Before I called the electrician I was trying to find information on how to do the grounding properly and I found information pointing towards this solution as well, but couldn't quite understand why it is the better way. When the electrician said that there's no difference I wanted to find out if that's actually the case. Thank you for clarifying why this is, indeed, the better way. Jul 15 at 8:55
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What you are describing sounds like a TN-C system where the neutral and ground are combined all the way to the sockets, where a "bootleg ground" is used to both the ground and neutral terminals.

In a TN-C-S system, the neutral and ground are split at the origin of the supply in the property, and they are never combined after that one splitting point. In the USA, it's normal for the neutral and ground to be split at the main breaker panel, while in the UK it's done at the supplier's main fuse. An electrician should know where it's done in your country.

TN-C has been prohibited in the UK for many years, because it has a huge safety problem. If a neutral wire ever breaks, while the live remains connected, then the ground terminal on every socket beyond that break will suddenly become live. So any any grounded appliances plugged in to those sockets will also become live.

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  • I read about the dangers of TN-C system as well and that's why I wondered if doing the connection of neutral and ground at one place (my apartment's circuit breaker board) would be safer since it seems this is my only option to get grounding. It has been prohibited here as well for new buildings but it is still legal to be done for older buildings. Jul 10 at 12:21
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I would just like to add, because it appears to not be mentioned, that combining/attaching/bonding the ground and neutral together should only be done once, and that singular place where the ground and neutral are mechanically/metallically joined should be at the service. The panel where the metering equipment is located. If you attached the ground and neutral together in one place (your panel for example) and then elsewhere in the system (an outlet, for example), you create what is sometimes called a "current loop". The current that the neutral normally carries will now split, with some current being carried by the neutral wire and some along the metallic components of your grounding system. A good analogy is taking a circular racetrack, then take one half of the circular race track and split the lanes apart. The cars on the track (the electrons) will still be traveling the same direction, but for a little while, will split apart, some will take one track, some will take the other track, then when the lanes re-join the electrons come back together. This would, if anything, ADD noise to the electrical system, not to mention, it is dangerous as the ground is not meant to be a normally current-carrying conductor.

That being said, if your apt is as old as you say, you M O S T likely have metal conduit in the walls, in which case, each outlet's ground terminal should be bonded to the enclosure that it is within, as long as the enclosure is metal. That is probably your best hope. If it is a plastic box that the outlet is housed inside, I'm sorry to say, you're looking at more of a full re-wire situation to have it set up the way you want. The neutral's and ground wires should NOT be tied together at the outlets. That is dangerous and will not improve your system.

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The practice of connecting neutral and ground prong in outlets is called "Zeroing" and is not advised. It does provide semi-ground and helps in case of short to washing machine chassis for example, BUT, if by some chance the neutral get interrupted somewhere from supply side (because it burned or fell out cheap backstab OR some lazy worker put a switch on wrong wire), the washing machine no longer has neutral OR ground, and the chassis itself becomes electrified. Pretty scary, yes?
(It will shock slightly less than holding live wire, because current has to go through machine heater/panel first, but still dangerous)

First thing to check - do your power sockets have two or three wires coming in?
If there is only two wires, you're cooked, and only way to get "proper" grounding is to rewire the sockets aka rip/add wires and make huge mess. If there is three wires (or metal conduits to the box or wire has a metal shell), there is hope you can get grounding without costly rewire. Check most/all sockets and note it down. Also a good moment to verify all wires are firmly in place. Turn off the power before poking fingers inside. A voltage probe is recommended.

Second thing to check - you need to get an electrician to take apart the fuse box and verify that the third wire/shell/conduit for every socket is indeed accessible there. If there is no separate ground, the neutral wire can be split in the box before RCD. If you want RCD, make sure you have enough space in the box, otherwise you need new panel. Expect to pay some money to electrician, but they are worth the job. If an additional grounding is needed, electrician may be able to bond the separated ground wire to water pipes (old houses had those heavy iron ones, they are perfectly grounded).

Third thing to check (but actually 1.5th thing) - do you have fuses before the main panel? Are they sealed / locked / otherwise inaccessible? You may need to contact the building manager / utility company to get access to those, as electrician will need to turn off the power to panel to work on it.

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  • Thank you for the clear answer. "Zeroing" is a really common method used here and after reading about the dangers of it, I asked electrician to do the rewiring from the panel. Current panel is from the 80's so new panel will be installed with RCD's. Unfortunately there is no third wire because the grid is old so I have to wait for the building management to hopefully renovate the whole grid in the future. Also, unfortunately, the water pipes have been replaced with plastic ones in the building which is good but takes away the possibility of grounding using those. Jul 16 at 11:43

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