Three-Phase RCD in Single-Phase Circuits: Standards, Acceptability & Whole Apartment Use

Is there any provision in the standards regarding the non-use of three-phase RCDs in single-phase circuits? Is it possible to question the solution with one 3-phase circuit breaker for the whole apartment when accepting the installation?

There is a provision that the RCD should be used for all socket circuits operated by unqualified persons (the famous "belongs" and "should", the importance of which is given by our legislator on an equal footing ...). Unfortunately, it is not clear what type of highly sensitive RCD should be used. Therefore, the installation cannot be questioned, especially if it is made in accordance with the design. And designers often place a three-phase RCD as a "panacea" and a compromise between duty and cost.

tehaceole wrote:

Therefore, the installation cannot be questioned, especially if it is made in accordance with the design. And designers often place a three-phase RCD as a "panacea" and a compromise between duty and cost.

Installation made in accordance with the design may be questioned if the design is not performed in accordance with the regulations and standards. The matter is then to be clarified between the contractor and the designer, but the investor should expect compliance with the regulations and standards.

Does anyone have any idea to enforce the use of single-phase RCDs in a newly constructed building, or is it impossible?

This is what I have in the project and the designer replied to my question that the installation was designed in accordance with applicable standards.

TWK wrote:

Is there any provision in the standards regarding the non-use of three-phase RCDs in single-phase circuits? Is it possible to question the solution with one 3-phase circuit breaker for the whole apartment when accepting the installation?

This solution makes it impossible to narrow down the area of searching for a random fault in the installation. This is against technical knowledge, but unfortunately it does not violate the law.
I advise you to change the designer, because it's just a cloud.

retrofood wrote:

I advise you to change the designer, because it's just a cloud.

The advice is especially valuable, if addressed to the contractor or (even better) subcontractors ...

If the investor is also a later resident, you can go to him. Arguments about savings of several hundred zlotys, at the cost of possible losses of several thousand, often reach the imagination.
It is worse if the investor is a developer who intends to build as cheaply as possible and sell as expensive as possible. Then there is no strength. And no one will convince him with any technical knowledge or potential losses for the inhabitants, because what is not forbidden is allowed.
Whoever worked for such people knows what we are talking about.

O^O wrote:

Whoever worked for such people knows what we are talking about.

Unfortunately...

The project already bought so mustard after dinner.

All the disadvantages of using the RCD 3-f instead of the 3x RCD 1-f mentioned in this thread are known to me. Nevertheless, thank you for submitting them. Collecting them in one place may have an educational value for the future.

As for the reasons for the question. Of course, when I do something, I take into account the functionality and reliability of the installation. But in this case, my role is slightly different: I was asked to participate in the acceptance of the apartment from the developer. For now, the building is a construction site and there is no power to the premises, but I went to inspect it. One of the comments I have is the 3-f RCD for the 1-f circuits. Unfortunately, I cannot do anything in this matter, because there is no basis for it in standards or regulations. But I am going to stick to other issues, such as the colors of the wires, and I will also verify the selectivity of the protection. I'll see what else comes out after applying the voltage.

Why don't you do anything?
It should all be described.
Note that one RCD has the characteristics of protection against electric shock, but such a solution contradicts the principles of technical knowledge and significantly reduces the functionality of the installation.
And present possible scenarios of a potential failure.

kkas12 wrote:

Why can't you do anything?

I will act, but I do not suspect that it will bring any effects ...

You can write papers about the selection of residual current devices, but this is probably not the point here, because every designer should be familiar with the issue taking into account the balance of the determined leakage currents in the protected circuit, taking into account the principles of technical knowledge or possible potential failure scenarios mentioned by Kkas12.
As I think, we agree that it is not appropriate to have one RCD protects the entire receiving installation, because excessive residual current in any receiving circuit causes the RCD to trip and deprives all circuits, including lighting, and poses a danger to users, which apparently does not appeal to to the designer for whom the investor-developer costs are the most important ...
In the case of using a 4-pole (not 3-phase) RCD in 3 single-phase circuits supplied from different phases, the highest value of the current in the PE conductor should be expected
when switching on one or two circuits, and not all three, and when designing more complex installations, one should not forget about the possible situations when, in addition to active currents, currents of a capacitive nature appear - the known problem of "incandescent" LED lamps or the measured voltage in the cable / circuit switched off
In fact - since the designer focused on saving - he used a residual current circuit breaker with a current of Ia = 30mA as the main switch of the switchgear and stated that everything complies with the standards and regulations, refer to
§ 183. 1. In electrical installations, the following should be used:
5- the principle of selectivity of security

This provision is de facto included in all protections - also residual current devices, not only overcurrent ...

At a neighbor's new house, an electrician (a licensed company) performed the entire electrical installation, in the design scheme there were 3 RDC-1 phase for individual circuits and 1 RCD-3 phase for "force" in the garage.

I was looking at the progress of the work. It was time to connect devices in the switchgear (the price for making the installation in the building along with the receipt, protocol, etc., was agreed earlier), and what I see, "es" as for a medicine probably with 5 pieces (including 16A and 10A), of course 1 RCD - 3 phase, and no overvoltage protection without its own protection, which is completely different than in the diagram.
A 3-row switchgear, so a lot of space, but what are the plugs for?
The mob and the clutter of cables under the switchgear faceplate are not visible anyway. :)

Nothing to do with it, but I asked the "specialist" why it looks the way it looks.
Literally said nothing. Both he and I knew it was about money and savings, which translates into greater profit for the contractor.

In addition, the "mesh" lighting circuit in the soffit outside was connected to the RCD.

To the point:

Middle of the night. Heating with a solid fuel stove (pumps, airflow, no gravity circulation), the householders are asleep and suddenly the RCD crashes. The furnace starts to crackle (because it is well filled for the night).
... and now it's lucky that the neighbor got up as needed and found that there was no power.
I run to the stove, everything is boiling there, rush to the switchboard, RDC disconnected, lever up, throws it away again. On the 12th time it turned on.

Conclusions.
The external circuit probably triggered the RCD from the dangling (not yet connected) cables getting wet from the fancy lights, 1 only RCD for the whole house, the effect is known.
I would also like to add that the lowest-end equipment probably Kan..x

A respected company from Lublin (I will not give the name, because I don't remember )
Installation patted, received, recorded, etc., etc.

Oh, and the switchgear, in addition, in a built-in closet.

It's probably worse than made in PRC.


If there is no such provision regulating whether the RCD should be 1F or 3F, it should absolutely be. And it should be ENFORCED

Zloty60 wrote:

Middle of the night. Heating with a solid fuel stove (pumps, airflow, no gravity circulation), the householders are asleep and suddenly the RCD crashes. The furnace starts to crackle (because it is well filled for the night).
... and now it's lucky that the neighbor got up as needed and found that there was no power.
I run to the stove, everything is boiling there, rush to the switchboard, RDC disconnected, lever up, throws it away again. On the 12th time it turned on.

A bad example, because replacing the RCD with a single-phase one would not do anything. If it happened that the same 1-phase RCD is connected to the stove and external lighting, the effect would be the same.
This is where additional protection is provided for receivers that do not require it at all.

O^O wrote:

A bad example, because replacing the RCD with a single-phase one would not do anything. If it happened that the same 1-phase RCD is connected to the stove and external lighting, the effect would be the same.

And do you think someone who isn't infected with morons would do the installation like your example?

PS. It is worth covering the external lighting with the operation of the RCD. It's just that you have to have all five staves in your head. And the contractor in question could have at most four.

retrofood wrote:

And do you think someone who isn't infected with morons would do the installation like your example?

And the current performance was less idiotic?

retrofood wrote:

PS. It is worth covering the external lighting with the operation of the RCD. It's just that you have to have all five staves in your head. And the contractor in question could have at most four.

It was not the outdoor lighting that I had in mind, but the stove.

O^O wrote:

retrofood wrote:

And do you think someone who isn't infected with morons would do the installation like your example?

And the current performance was less idiotic?

Not. Except that a moron could be lucky and randomly split circuits differently than in your example (if there were, for example, three differentials).

retrofood wrote:

Not. Except that a moron could be lucky and randomly split circuits differently than in your example (if there were, for example, three differentials).

Maybe yes or maybe not. Personally, however, I would prefer to rely on the expertise of the contractor and designer rather than the principle that "a stupid is always lucky".

Let's be honest - including the RCD of a stationary receiver, which does not require such additional protection (but requires continuous power supply!), Is even more stupid than using one RCD for the entire apartment.

In the case described by me, there was also a lack of elementary knowledge of the owner who fully trusted the installer. The neighbor didn't go into how it's done. (Maybe he didn't know each other, maybe he didn't have time to get into it) It works, it works. The installer, made, handed over the protocols, collected the salary. The owner was glad that everything was ok, because he was quick and efficient.

As for the curiosities, I still remember how the B16 also complained about the turning off of the B16 when turning on the large angle grinder. It is no wonder that there were not enough of these "es" and this circuit probably also serves the kitchen or other together :)

The installer had the knowledge and experience (I'm not saying that he did not), he only cut them on the materials.

All of them will not burn, do not propagate stupidity. In addition, in TN-C it is forbidden to use RCD not only because of a possible break in the PEN. It is not used because the possible short-circuit current to the housing would flow through the PEN anyway -> RCD could not work. The second reason is the current "escaping" from the housing of e.g. washing machine to the ground through the floor -> unnecessary RCD trip. You can read so often here " after connecting the stove to gas, the RCD crashes "this is the case.