Why it is "not allowed" to use 3-phase differentials in 1-phase instal

Hello.

Please explain to me. Why can't 3-phase differentials be used in 1-phase installations? I've had this opinion a few times. Is the main reason only that when a 3-phase differential works because something happens on one of the phases, all phases are disconnected? It's all about not turning off the lighting in the house by rummaging at the socket? Or is there a better reason?

Everyone writes that single-phase differentials should be given, but no one explains why?
For example, this year I received a flat in a block of flats, new, just built, and there I have a 3-phase differential and only this one. In my parents' house in the countryside, there is also only one 3-phase differential. Are these installations wrong?

Dude, nowhere does it say "not allowed".
Because it is allowed, but ... such conduct carries the risk of damaging 1-phase receivers connected to this apparatus.
Using one single RCD for the entire installation is simply taking the easy way out and maximizing cost reduction.
Later, during operation, aging of the installation (and receivers), unnecessary and unexpected actions can irritate healthily

Adam Ś. wrote:

Why can't 3-phase differentials be used in 1-phase installations?

It's okay, it's not illegal, but it's not recommended.

First of all, often all existing circuits are protected by a single 3-ph residual current device. In the event of a possible failure of the installation, causing the activation of this switch, we do not immediately have power in the whole house. In addition, the search for the source of failure is difficult.

The second issue is the possibility of non-simultaneous opening of the contacts of such a switch. Particular attention is drawn here to the situation in which the neutral contact is opened first, and only then the phase contacts. In this case (when there is a temporary lack of connection in the N line), the phase voltages may assume different values in the range of 0 V - 400 V (depending on the load of individual phases). For three-phase receivers, such a situation is not dangerous, while supplying a 230 V receiver with a voltage in the range of 253-400 V is dangerous. The load may or may not withstand this overvoltage, depending on the duration of the overvoltage. Manufacturers of differential circuits know this, which is why they use accelerated connection and delayed disconnection of the N circuit. The situation seems to be under control, but it is still possible to occur. Normally, this asymmetry would be much smaller. There must also be some coincidence of several circumstances. Firstly, the circuit breaker would have to be defective, secondly, the contacts would have to open "very long" and asymmetrically, thirdly, a very large single-phase load would have to be switched off, and all these things would have to happen just when a differential current of the order of the tripping current appeared security. And finally, even when such an overvoltage occurs for a short time, the devices will survive it.
The situation of damage to the devices is therefore 1-f unlikely, but possible. That's why it's safe to say, using 3f breakers for 3-f circuits and 1-f for 1-f circuits.

I agree with eppater. When a three-phase RCD trips, it is more difficult to find the cause, the place of leakage (and at that time the house is dark).

The world today is full of different opportunities. Who will say whether it is justified to use a three-phase, medium-sensitive RCD on the three-phase circuit and a single-phase, high-sensitivity right next to the receiver??

ssllaawweekk wrote:

Who will say whether it is justified to use a three-phase, medium-sensitive RCD on the three-phase circuit and a single-phase, high-sensitivity right next to the receiver?

It is no longer a slight exaggeration of form over substance ? It is probably better when the RCD is placed in the switchgear than at the receiver.

Approx. thank you for the information
One more thing. And is it possible to make a "differential tester to check if it works well? I know that the differential has a special button, but I mean something more like - some kind of resistor plugged into the socket or something. I'm asking because once I was doing something at the socket that was under voltage , I touched the phase wire and felt a tingle but the differential didn't work.

There are testers for this, current and time are selected. As the "differential" does not meet the above. values are garbage.

ssllaawweekk wrote:

When a three-phase RCD trips, it is more difficult to find the cause, the place of leakage (and at that time the house is dark)

For me it is very good. I just deal with locating faults in cables and installations. When there is no electricity in the whole house, the customer pays more willingly and more for the removal of the failure.
I'd like to thank everyone who saves differentials. That's why I am asking you to use "three essays and one differential".
Regards.
Conrad.
To save further, AC circuit breakers are commonly used.

There are simple testers available on the Internet for PLN 40, which, after plugging into the socket and pressing the button, test the operation of the RCD.

230V RCD mains socket tester - UNI-T UT07B-EU

Adam Ś. wrote:

Topic why "must not" use 3-phase differentials in 1-f installations

Not true, it's allowed.
A friend has a single-phase installation - no.
A friend has a 3-phase installation.
This is the correct but economical solution.

Buddy, what you read was about circuits - not installations.
Distinguish the installations from the circuits supplying the receivers.

Adam Ś. wrote:

I'm asking because once, while doing something at the socket that was live, I touched the phase wire and felt a tingling sensation, but the differential didn't work.

My friend !
Before you start checking something, get knowledge about installations.
If you touch phases and N, the current will kill you and the RCD has no right to work.

Hello .
Maybe I'm hurting others with my comment.
I have a 10-year-old installation made personally, in which I used 3-phase differential circuits for two switchgears, ground floor and first floor. So far, I have not had a problem with their operation. In the event of its activation, I can easily check what is the reason for its activation.
How?
- first of all, I will disconnect all receivers that are powered by a plug
-there is an induction hob that I will disconnect in the switchgear
- lighting remains, with which there is also no problem
Someone blue will ask what about the N and PE wires?
Also not a problem, because each wire has markers (numbered wires), so there is no problem for me.
Why so?, from a situation I had several years ago with a friend whose differential switch worked in rainy weather. After turning it on, everything was OK for about an hour, two, a random situation. In addition, one differential for the entire two-story house A large two-story house switchgears, but only one 3-phase differential. If I were to make a switchgear again, I would certainly use more of them, we are talking about 1-phase. I think that from a practical point of view, the differential is triggered mainly from receivers powered from a 230V socket, or permanently connected (induction or similar cooker), than from lighting.
I'm omitting bathroom lighting, lighting outside the building.

nikusert wrote:

I have a 10-year-old installation made personally, in which I used 3-phase differentials

I, on the other hand, have installations that are about 20 years old, protected by one three-phase differential. The entire installation works flawlessly.

As you brag about installations, my neighbor has a "mixed" installation Surface-mounted/under-floor. Some aluminum 2x1.5, some copper 2x1.5, and in the bathroom someone made a lighting installation with a 300ohm flat antenna cable and it only has 2 fuses :)

Interestingly, the installation has been operating for several decades with almost no failures ... Sometimes only the fuse blows.

He is an older man and he did not want to agree to any renovation of the installation - it worked for so many years, it will still last...

Adam Ś. wrote:

Why can't 3-phase differentials be used in 1-phase installations?

It is not forbidden. Friend @elpapiotr he described it clearly and basically exhausted the subject.

Adam Ś. wrote:

I'm asking because once, while doing something at the socket that was live, I touched the phase wire and felt a tingling sensation, but the differential didn't work.

Either you touched L and N at the same time (less likely), or if you only touched L, the current that flowed was probably too small to trip the RCD. Of course, I assume that the RCD is operational and the installation is done correctly.
Read about the effect of electricity on a person depending on its intensity. The current flow threshold is well below 30mA.

Michał643 wrote:

I, on the other hand, have installations that are about 20 years old, protected by one three-phase differential. The entire installation works flawlessly.

Here, too, it worked flawlessly for about twenty years.



Weeping and gnashing of teeth today.
Over 5,000,- the dog went up the ass.


So I propose to chill with paeans over a solution from the "obvious malpractice" category.

kkas12 wrote:

Michał643 wrote:

I, on the other hand, have installations that are about 20 years old, protected by one three-phase differential. The entire installation works flawlessly.

Here, too, it worked flawlessly for about twenty years.



Weeping and gnashing of teeth today.
Over 5,000,- the dog went up the ass.

So I propose to chill with paeans over a solution from the "obvious malpractice" category.

How does this relate to the topic? A colleague in the next topic shows a photo, but the reason for burning the differential is completely unrelated to the topic Untightened cable (loose) and such an effect. But how does this relate to the topic?

adversus wrote:

.... but the reason for burning the differential is completely unrelated to the topic ....

For a layman, maybe not, but for a (conscious) electrician, it is not the cause that is important, but its effect.

So praise your pseudo-saving solutions, just remember that dogs eat cheap meat and what was acceptable at the beginning of the RCD era does not have to be used in its unchanged form (or even should not) today.

So sorry my friend, but photos will always be found where a solution that is not suitable for the 21st century will be propagated.

Personally, I tolerate a four-circuit RCD only in the power supply of a small construction site.

Michał643 wrote:

Manufacturers of differential circuits know this, which is why they use delayed switching on and off of the N track

Please, dear friend, rather the other way around:
- accelerated connection and delayed disconnection of the N circuit .

clubber84 wrote:

accelerated connection and delayed disconnection of the N circuit

I've corrected it, obvious error

kkas12 wrote:

So praise your pseudo-saving solutions, just remember that dogs eat cheap meat and what was acceptable at the beginning of the RCD era does not have to be used in its unchanged form (or even should not) today.

Exactly. The problem begins when the user connects the existing installation (with one four-pole RCD), e.g. plugs in induction hob, ceramic (with heaters).
All the boards I have seen are powered from two phase voltages, and the connection power of these boards is mostly about 7.2 kW.
Such a device at maximum power forces the current consumption of about 15.5A per phase (rms value), then what current flows in the neutral?
Average 26.9A.
I wrote on average because due to the work of a household appliance service technician, I happened to capture with clamps the current flowing through the N field (in RCD 4-P 25A / 30mA) of the order of 35A, because there was still a washing machine, dryer, electric kettle ... on the same phase used in same time by induction.

kkas12 wrote:

Here, too, it worked flawlessly for about twenty years.

Such a view is no stranger to me, after firing the neutral, devices with low power consumption were especially hit. Where, as it turned out, the power consumption was distributed asymmetrically, after adding the above-mentioned devices by the existing RCD.
To sum up, the neutral (in the section after the N/PE division) is the most and most frequently loaded cable in a household installation. At the same time, it is so important in the case of a 3-phase connection (in the event of a break) not to hurt yourself in the future.

iskrownik wrote:

Exactly. The problem begins when the user connects the existing installation (with one four-pole RCD), e.g. plugs in induction hob, ceramic (with heaters).
All the boards I have seen are powered from two phase voltages, and the connection power of these boards is mostly about 7.2 kW.
Such a device at maximum power forces the current consumption of about 15.5A per phase (rms value), then what current flows in the neutral?
Average 26.9A.
I wrote on average because due to the work of a household appliance service technician, I happened to capture with clamps the current flowing through the N field (in RCD 4-P 25A / 30mA) of the order of 35A, because there was still a washing machine, dryer, electric kettle ... on the same phase used in same time by induction.

Colleagues, don't exaggerate because somehow you can't hear about a series of burned differential circuits all over the country in thousands of pieces, because they would already be trumpeting on TV, don't exaggerate .... Especially since it's like that every installation Janusz does business and about failures, after all, on a national scale doesn't bother. So calmly.

P.S. Because everyone with ceramic plates cooks a meal for the army regiment 3 times a day in all fields and at full blast.

adversus wrote:

iskrownik wrote:

Exactly. The problem begins when the user connects the existing installation (with one four-pole RCD), e.g. plugs in induction hob, ceramic (with heaters).
All the boards I have seen are powered from two phase voltages, and the connection power of these boards is mostly about 7.2 kW.
Such a device at maximum power forces the current consumption of about 15.5A per phase (rms value), then what current flows in the neutral?
Average 26.9A.
I wrote on average because due to the work of a household appliance service technician, I happened to capture with clamps the current flowing through the N field (in RCD 4-P 25A / 30mA) of the order of 35A, because there was still a washing machine, dryer, electric kettle ... on the same phase used in same time by induction.

Colleagues, don't exaggerate because somehow you can't hear about a series of burned differential circuits all over the country in thousands of pieces, because they would be trumpeting on TV, don't exaggerate .... Especially since it's like that every installation is made by Janusz of business and about failures, after all, on a national scale doesn't bother. So calmly.

P.S. Because everyone with ceramic plates cooks a meal for the army regiment 3 times a day in all fields and at full blast.

No one is exaggerating, just warning correctly.

It is better to warn than to cry later because of a fire caused by poorly made electrical installation.

iskrownik wrote:

Exactly. The problem begins when the user connects the existing installation (with one four-pole RCD), e.g. plugs in induction hob, ceramic (with heaters).
All the boards I have seen are powered from two phase voltages, and the connection power of these boards is mostly about 7.2 kW.
Such a device at maximum power forces the current consumption of about 15.5A per phase (rms value), then what current flows in the neutral?
Average 26.9A.
I wrote on average because due to the work of a household appliance service technician, I happened to capture with clamps the current flowing through the N field (in RCD 4-P 25A / 30mA) of the order of 35A, because there was still a washing machine, dryer, electric kettle ... on the same phase used in same time by induction.

kkas12 wrote:

Here, too, it worked flawlessly for about twenty years.

Such a view is not strange to me, after firing the neutral, devices with low power consumption were especially hit. Where, as it turned out, the power consumption was distributed asymmetrically, after adding the above-mentioned devices by the existing RCD.
In sum neutral (in the section after the N/PE division) is the most and most frequently loaded conductor in the installation household. At the same time, it is so important in the case of a 3-phase connection (in the event of a break) not to hurt yourself in the future.

1. Can you answer what I bolded? How come on two phases loaded with 15.5A current through 2 similar receivers (left and right side of the board) the neutral current flows as much as 26.9A?
2. Load has nothing to do with it. In this section, the current of the neutral conductor is added algebraically (if it is connected to the 1f RCD, but the cable should be matched to the current. If it is connected to the 3f RCD, it adds geometrically and is no longer loaded with the cable. Why do they burn up? RCD terminals with wires. This is because rationalizers looking for further savings pack several wires under one terminal, sometimes even with different cross-sections. further savings on wire bridges.

iskrownik wrote:

Exactly. The problem begins when the user connects the existing installation (with one four-pole RCD), e.g. plugs in induction hob, ceramic (with heaters).
All the boards I have seen are powered from two phase voltages, and the connection power of these boards is mostly about 7.2 kW.
Such a device at maximum power forces the current consumption of about 15.5A per phase (rms value), then what current flows in the neutral?
Average 26.9A.

The basics of electrical engineering, or physics, or simply mathematics, bow down. Somehow I haven't seen three-phase wires with a thicker N conductor. And from this weak argument of my friend, it turns out that N should be thicker than the other phases. Well, not everyone is an eagle

Hello,


Ladies and gentlemen, this thread is getting off topic. The case concerned - why 3-phase differentials must not be used in 1-phase circuits.

Colleagues elpapiotr and Michał643 explained why it is not recommended. but there is one more but: in some differentials there was a test between the phases before and after the differential. So if you had only one phase connected, the Test button might not work properly.

Telex wrote:

The case concerned - why 3-phase differentials must not be used in 1-phase circuits.

Not true. You're bending the core of the theme in an unacceptable way.

The essence is the use of four-circuit RCDs to protect single-phase circuits supplied from different times.
Although such a solution meets the principles of protection against electric shock, it does not have much in common with a professional solution.

Ktoś_tam wrote:

1. Can you answer what I bolded? How come on two phases loaded with a current of 15.5A through 2 similar receivers (left and right side of the board) the neutral current flows as much as 26.9A?

Note one thing, each induction is a non-linear receiver and, therefore, mainly a large garbage collector of the third harmonic of the current (rarely when the share of the third harmonic of the phase current goes below 30%), and these, unfortunately, add up algebraically in the above-mentioned case in the neutral wire. If the load were purely resistive, the current in the neutral would be no greater than the phase currents.
I must admit that I was surprised by the customer's measurement value. I took the plate to the workshop and repeated the measurements. For me it came out less, about 24A in the neutral (lower supply voltage due to the end of the line) and in this way I found out why the manufacturer used two terminals for N wires.
Anticipating further questions:
This report was for too high power supply voltage on the right side (E3), the board had a preliminary measuring circuit that did not allow the relay to be turned on and thus further havoc. The reason was the melting of the N field in the RCD 25A, fortunately, a customer dedicated only to the board.

adversus wrote:

The basics of electrical engineering, or physics, or simply mathematics, bow down. Somehow I haven't seen three-phase wires with a thicker N conductor. And from this weak argument of my friend, it turns out that N should be thicker than the other phases. Well, not everyone is an eagle

Yes, they bow when only the 50Hz fundamental frequency is considered. For you to read below, from page 5, the specifics are described.