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YDY Cable 3x1.5 vs 3x2.5: Conduit or No Conduit for Ground Floor Apartment Installation

gintur 60201 33
Best answers

Should I run the apartment socket circuits as 3x2.5 YDYp directly in the floor/skirting channels, or put them in conduit/installation pipe, and is 3x1.5 acceptable?

Use 3x2.5 mm² for socket circuits, and leave 1.5 mm² for lighting; 3x2.5 YDYp is enough and is usually easier to lay than a round cable [#5002975][#5003554] If you want mechanical protection and the possibility of later replacement, prefer a rigid PVC installation pipe or a cable tray/channel rather than a flexible conduit/peszel, because pulling 3x2.5 through a 13x18 pipe with bends is very difficult [#5003554][#5002562][#5002783] For underfloor runs, a tray/channel makes sense mainly as protection and for future additions, not because replacement will be easy later [#5003378][#5006752] If you run the cable in a floor groove/screed, flat YDYp needs a smaller chase than a pipe, but any underfloor installation will be harder to repair later [#5002975]
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  • #1 4999298
    gintur
    Level 10  
    The installation will be replaced in the apartment, the electrician did some research, he drew what where and how. He stated that the sockets in the rooms should be equipped with 3x1.5 YDYp and let it go without forging in the skirting board. However, the situation has changed a bit because it turned out that there is some kind of the insulating board is then roofing felt and screed, i.e. practically only sand (apartment on the ground floor) Unfortunately, the roofing felt sticks out in the middle, the screed is quite cracked and give it all an unpleasant smell in the apartment. all over the apartment. I wonder if I will use these corridors to lay wires. Now I do not know whether to use 3x2.5 YDYp and that is enough or to use 3x2.5 round but in a conduit? What is your advice?
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  • #2 4999405
    harlejowiec
    Level 25  
    I would give a conduit, the cost is higher, but if necessary, the cable can be replaced.
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  • #3 5002562
    Wakmen
    Level 11  
    As far as I know, the power supply to the sockets should be a 3x2.5 cable.
    harlejowiec wrote:
    I would give a conduit, the cost is higher, but if necessary, the cable can be replaced.

    Sure, you can, but is it always possible to replace 3x2.5 in a 13x18 pipe so easily in the corners of the rooms? I guess there's little chance. I understand it on a straight section, but if the conduit is 12m long, for example with 3 bends, it is rather impossible. You'll rip it out faster, I'll replace it.
  • #4 5002783
    jarecki 86
    Electrician specialist  
    Quote:
    is it always possible to replace 3x2.5 in a 13x18 pipe without any problems in the corners of the rooms? I guess there's little chance

    probably none, because it's not the diameter of the conduit.
  • #5 5002975
    Anonymous
    Anonymous  
  • #6 5003378
    krzychol66
    Level 25  
    You can still consider whether it would not be better to place a plastic cable tray in the screed or plaster. If you need to add some wires or replace some, you can tear off the strip, open the cover of the channel and easily do what you need.
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  • #7 5003489
    gintur
    Level 10  
    I'm just wondering about the trays, but will the 3x2.5 flat cable fit in such a tray? The round wire will come in without a problem, but it is more expensive in the castorama, I looked at it, 3x2.5 round costs PLN 5 per meter.
    I looked on the internet and found rigid electrical installation pipes, can such pipes be placed under the spout? In the product description it is written that it is only suitable for wall-mounted installations. Conduit - I'm afraid that the spout will freeze and if there are tensions, it may damage the conduit.
  • #8 5003554
    Madrik
    VIP Meritorious for electroda.pl  
    marcint2525 wrote:

    3x1.5 mm² YDYp per socket? The socket circuits are made of a 2.5 mm² cable. 1.5 mm² for lighting !!!


    Not true :D and before you jump on me, the sockets are powered with a cable with a cross-section selected in terms of the planned load and with a specific voltage drop.
    The fact that in an apartment building this cross-section for most sockets with a load capacity of 10A and at small distances is 2.5mm2 is a coincidence, not a rule. It may well turn out that in some applications 2.5mm2 will be too weak, and vice versa - 1.5mm2 may be completely sufficient. Half the trouble, if you give a larger cross-section ... But what about cases when a "faithful professional" powers a 2.5mm2 socket, and a "four" is needed? :)
    So, be careful with such statements, because they stick in the memory and are difficult to eradicate later.
    Just because the rule works "often" doesn't mean "always".

    I would suggest, instead of a conduit, give PVC installation pipes. They are stronger and it is easier to replace the cable in them than in the PESzel. Of course, the cost is higher, but it is not a makeshift plaster wall, but a floor, which is unlikely to be improved and redone in 5 years.
    Moreover, the conduit tends to undulate during laying. The tube is simple. Then pulling the cable through such a snake-like tunnel is a job for a desperate person, especially at bends.
    It is enough to pull a thick fishing line or wire into the tube and only pull the entire bundle of wires.
  • #9 5003637
    Anonymous
    Anonymous  
  • #10 5003697
    krzychol66
    Level 25  
    And the legal basis, Mr. Inspector, is able to quote?
  • #11 5004606
    Anonymous
    Anonymous  
  • #12 5004859
    krzychol66
    Level 25  
    Well, I would like to know in the context of the attached table of cable load capacity, which provision cited laboriously by the pre-pioneer prohibits the use of a YDYt 3x1.5 cable for powering sockets in the building for protection
    Attachments:
    • obciazalnosc_przewodow.pdf (35.08 KB) You must be logged in to download this attachment.
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  • #13 5004892
    jarecki 86
    Electrician specialist  
    marcint2525 , a lot of these laws and regulations, but just right absolutely nothing does not follow from them.
    This is not literature, my friend.
    Besides, in buildings not all socket circuits are of general purpose.

    The role of the site inspector is to check that the work has been carried out in accordance with the building design.
    So much and so much.
    And it's good to know the specific rules.
  • #14 5005179
    gintur
    Level 10  
    I decided to do it in this way, everywhere around the walls, channels will be cut out in the screed. In the trays, a rigid protective pipe (not a conduit) with a diameter of 18mm will be placed. The YDYp 3x2.5mm2 cable will be inserted into the pipes, then the entire corridor will be filled with assembly foam, and at the very end the screed will be placed in the whole apartment. Can the cable in the tube be covered with foam, is it a good way?
  • #15 5006396
    Anonymous
    Anonymous  
  • #16 5006648
    jarecki 86
    Electrician specialist  
    1. What is the long-term load capacity of 1 DY 4 mm2 core for the presented case?
    2. In the absence of "zero", after switching on only one load, the phase-to-phase voltage was shown on it?
    3. What effect does "zero" in the installation have on the operation of 3-phase devices?
    4. What are RL pipes intended for?

    Instead of mindlessly copying standards from the Internet, look for "inspector" answers to the questions asked.
    In case of any problems, I suggest asking a student from the "professional" school.


    :arrow: Happiness out of place!
    j.
  • #17 5006718
    HeSz
    Electrician specialist  
    Mr. Superintendent. You know the rules, but you don't read them!
    In the PN-IEC 60364-5-52:2002 standard you quoted "Electrical installations in buildings - Selection and assembly of electrical equipment - Wiring" on page 17 there is "Table 52J - minimum cross-sections of wires", and in it "like a bull" it is written : for fixed installation, cables and insulated wires, in lighting and POWER circuits, the minimum cross-section is: 1.5 mm^2 for copper and 2.5 mm^2 for aluminium.
    Regards

    :arrow: Docinki out of place!
    j.
  • #18 5006752
    MakroSerwis
    VIP Meritorious for electroda.pl  
    gintur wrote:
    The installation will be replaced in the apartment, the electrician did some research, he drew what where and how. He stated that the sockets in the rooms should be equipped with 3x1.5 YDYp and let it go without forging in the skirting board. However, the situation has changed a bit because it turned out that there is some kind of the insulating board is then roofing felt and screed, i.e. practically only sand (apartment on the ground floor) Unfortunately, the roofing felt sticks out in the middle, the screed is quite cracked and give it all an unpleasant smell in the apartment. all over the apartment. I wonder if I will use these corridors to lay wires. Now I do not know whether to use 3x2.5 YDYp and that is enough or to use 3x2.5 round but in a conduit? What is your advice?


    If you run from the bottom, the use of a cable tray may make sense in terms of protecting the cable and possibly plugging in the tap, if there is a need to add a socket in the future. There is no point in dwelling on the possible replacement of wires - an unlikely case.
  • #19 5007320
    gintur
    Level 10  
    A question for Mr. marcint2525 - that is, the wire that goes from the differential to the zero rail must have a cross-section of 10mm2, even though it will be really short?
    I asked the electrician to replace the cable from the security in the basement to the meter with a copper one. The electrician went down to the basement, looked at it and said that I need to buy a 3x4mm2 cable, i.e. phase zero and PE cable, which, as he said, "in the basement there is an equalization rail on the ceiling that needs to be drilled and with fasten the PE wire with the screws and now the question arises for me, if at home in the box, the wire from the differential to the zero bus is to be 10mm2, can the wire from the basement to the meter be 3x4mm2, because it turns out that 4mm enters the differential and is supposed to come out 10mm2? to attach if such a wire from the basement is replaced? How to solve it so that it is good?
  • #20 5007793
    Łukasz-O
    Admin of electroenergetics  
    I also have a question for the "inspector" Is the cause of burning the "zero" sometimes a loose contact or badly tightened?
    The same situation would be if you used even 25mm2.
    Besides, loose contact is not only the electrician's fault, but above all the lack of maintenance for a number of years.

    Buddy, like "there is no electricity" and in this case you only have a phase everywhere in the entire building, you always start work by unscrewing the switchgear. You would find the cause right away and not run around the house looking for phase-to-phase voltage in the socket. These 20 years must have been my colleague sitting behind the desk. Sorry, I wasn't going to write anything on this topic, but I couldn't.
  • #21 5007831
    jozefg
    VIP Meritorious for electroda.pl  
    :arrow: Either you will discuss the merits - or yellow cards will fall!
    Enough teasing!
  • #22 5007876
    Anonymous
    Anonymous  
  • #23 5009250
    jarecki 86
    Electrician specialist  
    gintur wrote:
    YDY cable with or without conduit?


    Of course, in a conduit - I suggest RKGL 20 x 14.5 with a reinforced strength of 320N. It must be ensured that during pouring concrete does not pour into the pipe, thus preventing possible replacement of the pipes.

    jozefg wrote:
    Either you will discuss the merits - or yellow cards will fall!


    The thing is that it is impossible to conduct a substantive discussion in a situation where the provoking party avoids any answers to the questions asked.
    So if we are left with a choice between accepting the absolute right inspector and silence, I choose the latter.
  • #24 5009351
    HeSz
    Electrician specialist  
    And I am asking for a comment on the standard I quoted!

    Added after 1 [minutes]:

    This post is about "marcint2525"
  • #25 5009715
    filip.s
    Level 23  
    marcint2525 wrote:
    "(Question: Which colleague will say what is the Long Term Rating Limit for this cable?)."


    "output to the feeder rail, the connection is to be made LG16mm^2 (terminals soldered or a clamped sleeve)."
    Added after 6 [minutes]:



    16mm² is more or less from 50 to 80A, depending on the environment in which it is located, and as for the connections in the switchgear, what standard says that an LGY cable must be used? I have been using DY for many years and somehow no one has had any doubts about the switchgear in my implementation :)
  • #26 5009746
    Anonymous
    Anonymous  
  • #27 5009779
    HeSz
    Electrician specialist  
    My post was about MINIMUM cross-sections. This does not mean that other parameters such as long-term load capacity, short-circuit strength or voltage drop should not be taken into account. The comment concerned only that it was a mistake to order installations with a cross-section below 2.5mm^2 without analyzing the circuit.
  • #28 5009789
    Łukasz-O
    Admin of electroenergetics  
    jarecki 86 wrote:


    The thing is that it is impossible to conduct a substantive discussion in a situation where the provoking party avoids any answers to the questions asked.
    So if we are left with a choice between accepting absolute reason inspector and silence, I choose the latter.

    Oh right there.

    My friend marcint2525 really no offense. If I offended you, I apologize, but you never answer the question asked or you answer casually. How can you talk meaningfully like this?
    All the time you refer to regulations, technical knowledge or standards - ok I understand, but why when you write posts (not only in this topic) you often contradict yourself, then (after checking in the manual or somewhere on the internet) you agree with others, and finally you cancel everything and you start over. I'm sorry, but that's how I see it.

    Since in your example it is:
    Quote:
    In the example given by me, the conditions require that the power wires have a cross-section of 10 mm^2


    What fungus is this for:
    Quote:
    That is, from the pole to the YKY 4x35mm^2 connector, from the connector to the YKY 5x35 meter and from the meter to the YKY 5x35mm^2 switchgear.


    Now my friend's question:
    Quote:
    There should be a LG 16mm^2 line. (Question: Which colleague will say what is the Long Term Rating Limit for this cable?).

    And is Lg 16mm2 a cable?


    Maybe I misunderstood your post :cry:
  • #29 5009798
    Anonymous
    Anonymous  
  • #30 5009799
    Madrik
    VIP Meritorious for electroda.pl  
    marcint2525 wrote:
    Quote:
    Minimum cross-section of a permanently laid cable, protected against damage
    mechanical, is 1.5 mm² Cu. accepts the minimum cross-section of the wires
    in electrical installations arranged inside buildings, for lighting circuits
    - 1.5 mm² Cu, for plug sockets - 2.5 mm² Cu.

    ...a quote from the first Electrician Installer's guide


    So the minimum is 1.5mm2... The phrase "Assumed" cannot be a legal basis, but only a guideline or recommendation, Mr. Inspector.
    Simply put - if such a cross-section would be sufficient in a given case, ordering its change, you are simply abusing your power, relying on the common opinion and having deep in ... your pocket, the basic laws of electrical engineering.
    Although in truth, it is rare for a "half-torque" to meet all the power requirements.

    marcint2525 wrote:
    and I will not allow your installation to move.


    Another thing is that the Inspector is currently God on the job, and he can order the entire installation to be changed, because he does not like the color of the sockets...
    Because to whom to appeal? To his friend in the area?
    But that doesn't mean he's right or infallible. Sometimes, such an inspector can be just stubborn or mean.
    And unfortunately, an ordinary electrician has to live with it and kiss both assholes, as long as the job goes through and not hear such a text as quoted.
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Topic summary

✨ The discussion revolves around the installation of electrical wiring in a ground floor apartment, specifically debating the use of YDYp cables with different cross-sections (3x1.5 mm² vs. 3x2.5 mm²) and whether to use conduit or not. Participants express concerns about the structural conditions, such as cracked screed and roofing felt, which may affect the installation. Recommendations include using 3x2.5 mm² cables for socket circuits, considering the installation of a conduit for easier cable replacement, and the potential use of plastic cable trays for future modifications. The importance of adhering to electrical regulations and standards is emphasized, with some participants advocating for stronger cable options to prevent issues related to load capacity and safety.

FAQ

TL;DR: In Polish flats, 2.5 mm² copper can carry ~24 A continuously [PN-IEC 60364] yet “swap-out becomes near impossible after three bends” [harlejowiec, 4999405]. Use rigid 18 mm conduit plus 3×2.5 YDY to future-proof sockets. Why it matters: Repairing a buried run later can cost 3× more than installing conduit now.

Quick Facts

• 3×2.5 mm² YDY flat: ≈24 A long-term current capacity in concrete [PN-IEC 60364-5-523]. • 18 mm rigid PVC conduit (RKGL 20 × 14.5): crush strength 320 N; floor-rated [jarecki 86, 5009250]. • Retail price: YDYp 3×2.5 flat ≈2.50 PLN/m; round ≈5 PLN/m [gintur, 5003489][saimon79, 5009887]. • PN-IEC 60364-5-52 minimum socket conductor: 1.5 mm² Cu; many inspectors enforce 2.5 mm² [HeSz, 5006718]. • Practical pull limit in corrugated conduit: <10 m with 3 bends for 3×2.5 mm² [Wakmen, 5002562].

What cable size should I run for apartment socket circuits?

Most Polish electricians specify 3×2.5 mm² Cu for general-purpose sockets because it supports ≈24 A and 2.5 kW heaters safely [Anonymous, 5009746]. Smaller wires risk overload when multiple appliances share one circuit.

Is 1.5 mm² ever allowed for sockets under Polish standards?

PN-IEC 60364-5-52 sets 1.5 mm² as the minimum for fixed power circuits, but only if load, voltage drop, and protective devices keep current below 16 A [HeSz, 5006718]. Many site inspectors still reject it outright, so confirm before installation [Anonymous, 5003637].

Flat YDYp vs round cable—does shape matter under a screed?

Only mechanically. Flat YDYp needs a shallower chase and costs less; round fits more easily in trays and pipes but doubles price per metre [gintur, 5003489]. Electrical ratings are identical when conductor size matches.

Do I need conduit if I lay cables in the floor screed?

Conduit isn’t mandatory, but it protects against cracked screed and lets you pull extra wires later. Without it, repairs mean breaking concrete [harlejowiec, 4999405]. Risk rises on ground floors where moisture and settlement occur.

Which conduit type works best under concrete floors?

Rigid PVC pipe (e.g., RKGL 20 × 14.5) stays straight and has 320 N crush strength, so cables pull easily even years later [jarecki 86, 5009250]. Corrugated flex conduits can kink and trap cables during bends [Madrik, 5003554].

How wide a chase do I need for 3×2.5 YDYp without conduit?

A 10–12 mm deep by 18–20 mm wide groove usually suffices, leaving ≥5 mm cover to meet mechanical-protection rules [PN-EN 50086-1].

Can I fill the conduit or cable run with expanding foam?

Foam around, not inside, the pipe is fine. Filling the tube blocks future pulls and traps moisture; use cement grout instead at entry points [Anonymous, 5006396].

What’s the risk if the neutral conductor burns out?

A lost neutral can put 400 V across single-phase devices, destroying electronics; one case caused ≥30 000 PLN damage [Anonymous, 5006396]. Loose terminations, not small cross-sections, are the usual culprit [Łukasz-O, 5007793].

How much current can a 16 mm² copper earthing conductor handle?

In air it carries ~76 A continuously, giving a 6 kA short-circuit limit for 0.2 s faults [PN-IEC 60364-5-523].

How do I pull a replacement cable through rigid pipe?

  1. Push a nylon fish tape or 2 mm shepherd’s wire through the empty pipe.
  2. Tie on the new 3×2.5 YDY with insulating tape.
  3. Lubricate lightly and pull steadily from the far end. One person pushes, one pulls for runs >8 m [Madrik, 5003554].

What’s the cheapest place to buy 3×2.5 cable in Poland?

Forum users report electrical wholesalers selling YDYp 3×2.5 for about 2.50 PLN/m—half the DIY-store price [saimon79, 5009887].

How to deal with inspectors who demand 2.5 mm² everywhere?

Show load calculations proving compliance, then request written refusal if they object. You can appeal to the Voivode to review their licence [HeSz, 5009856]. One installer replaced 1.5 mm² with 2.5 mm² rather than fight, adding one day and <200 PLN cost.
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