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3-phase cable size for 25kW load over 50m distance—what cross-section to choose?

wbmike 43824 20
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What cable cross-section should I use for a 25 kW three-phase load over 50 m?

To feed a 25 kW three-phase load over 50 m, the thread suggests an aluminum YAKY 4x16 mm² cable as theoretically sufficient, because its long-term thermal load is 85 A while the expected current is under 50 A and the voltage drop is about 1.4% [#9647124][#9647076] However, another reply says that if you follow the N SEP-E-002 limit of 0.5% voltage drop, you should choose YAKY 4x25 mm² aluminum instead [#9647193] That same reply estimates the 50 m YAKY 4x25 cable cost at under PLN 400 [#9647193] The discussion also notes that aluminum is much more economical than copper for this kind of run [#9647045][#9647099] So, 4x16 mm² was treated as acceptable in practice by one answer, but 4x25 mm² is the safer choice if you want to stay within the stricter voltage-drop limit [#9647124][#9647193]
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  • #1 9646896
    wbmike
    Level 10  
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    Hello, I have a question for experts. I have to lay the cable 50m away to draw electricity from the main box to my private box, which will be connected to 7 eateries. The power I have is 25KW. Which cable to use? I will add that it is a 3-phase current. Sorry for the unprofessional vocabulary, but as you can see I'm a beginner in energy.
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  • #2 9647015
    Miniax
    Electrician specialist  
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    First, what network layout?
    Secondly, if you say that a beginner, maybe it is worth outsourcing it to a professional?
  • #3 9647045
    wbmike
    Level 10  
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    I don't know what network layout. I commissioned a specialist and he says that 1mb of such a cable is about PLN 30 but I did not ask what it was about. So when I started to load now, I think he means yky 5x16mm, and hence my question, is it possible to mount a cable with a smaller cross-section, e.g. 5x10mm or on an aluminum one? I want to minimize costs because this connection is only for 2 months.
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  • #4 9647076
    Miniax
    Electrician specialist  
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    Theoretically, the YAKY 4X16 mm ^ 2 should be enough for you
  • #5 9647078
    Słonik1963
    Level 16  
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    It doesn't matter how long you connect users.

    For such power (current consumption) it is suitable.
    One more thing - how is it to be "arranged": by the ground, overhead, on structures, etc.

    Its price depends on the manufacturer (and the wholesaler who sells it).

    Remember, however, that when using a smaller cross-section, its damage may (and will certainly occur) - which will be associated with re-arrangement (and purchase), i.e. costs.
  • #6 9647099
    jarecki 86
    Electrician specialist  
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    And this power of 25KW is the connection power to the building, or for these 7 apartments?
    It is definitely much more economical to install an aluminum cable.
  • #7 9647110
    wbmike
    Level 10  
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    Miniax wrote:
    Theoretically, the YAKY 4X16 mm ^ 2 should be enough for you



    And in practice, it may turn out to be too weak?
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  • #8 9647124
    Miniax
    Electrician specialist  
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    wbmike wrote:
    Miniax wrote:
    Theoretically, the YAKY 4X16 mm ^ 2 should be enough for you



    And in practice, it may turn out to be too weak?


    The long-term thermal load of this cable is 85 A, while at 25 kW, the power consumption will not exceed 50 A.
    As for the voltage drops on this section, there will be about 1.4%, which is perfectly acceptable. So if there are no restrictions and you will connect to TN-C or TT, it will probably be enough.
  • #9 9647135
    wbmike
    Level 10  
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    jarecki 86 wrote:
    And this power of 25KW is the connection power to the building, or for these 7 apartments?
    It is definitely much more economical to install an aluminum cable.


    Conditions are issued for parking. This is what I wrote in the contract, which means that they do not know anything about the premises at the power plant.
  • #10 9647145
    Słonik1963
    Level 16  
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    There is also the question of the chapter - that is, the mailbox to which the users you write about will be connected.
    So the box, 7 fuses and FR in front of them - these are also costs.

    And will you settle them on the basis of the lump sum or the sub-meters?
  • #11 9647158
    wbmike
    Level 10  
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    Słonik1963 wrote:
    There is also the question of the chapter - that is, the mailbox to which the users you write about will be connected.
    So the box, 7 fuses and FR in front of them - these are also costs.


    I know that, but probably the most expensive cable of all this.
    From the sub-counters, I also know I have to buy them.

    A year ago, I was doing the same things, but I did not go into the topic of electrics, but commissioned everything to a specialist. This year it turned out that the boxes and cables that were installed a year ago are gone, probably someone had stolen them.
  • #12 9647163
    Słonik1963
    Level 16  
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    50x34 PLN = 1700
    Accessories about 200, box 100, labor 400 = 700

    But that's just a guess.

    Added after 2 [minutes]:

    And only if you attach them permanently, using "power" sockets a little more expensive (for sockets). And the same goes for the counters.
  • #13 9647193
    jarecki 86
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    Miniax wrote:
    As for the voltage drops on this section, there will be about 1.4%, which is perfectly acceptable

    Unfortunately, the N SEP-E-002 standard allows only 0.5% drop, so the appropriate cross-section of the Alu cable will be 25mm2. The cost of the 50 m YAKY4x25 will be less than PLN 400.
  • #14 9647194
    Słonik1963
    Level 16  
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    I suppose from your statement that the cable was lying on the ground or hanging.
    Bury it - the thief will have more problems with theft.
  • #15 9647208
    wbmike
    Level 10  
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    jarecki 86 wrote:
    Miniax wrote:
    As for the voltage drops on this section, there will be about 1.4%, which is perfectly acceptable

    Unfortunately, the N SEP-E-002 standard allows only 0.5% drop, so the appropriate cross-section of the Alu cable will be 25mm2. The cost of the 50 m YAKY4x25 will be less than PLN 400.


    Well, PLN 400 is not PLN 1700. Tomorrow I'll talk to an electrician and say I want an aluminum cable.
  • #16 9647214
    Miniax
    Electrician specialist  
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    jarecki 86 wrote:
    Miniax wrote:
    As for the voltage drops on this section, there will be about 1.4%, which is perfectly acceptable

    Unfortunately, the N SEP-E-002 standard allows only 0.5% drop, so the appropriate cross-section of the Alu cable will be 25mm2. The cost of the 50 m YAKY4x25 will be less than PLN 400.


    As far as I know (although I will not cut my hand), the standard quoted by you is not obligatory and depending on the needs and requirements, a decrease of 1.4% is acceptable, of course, nothing prevents you from using a larger cross-section.
  • #17 9647223
    Słonik1963
    Level 16  
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    The price of the natural YAKY 4x25mm2 (I was just looking - internet) - 7.46 / m.
    It may differ (by a dozen or so groszy) - it depends on the wholesaler.
    50x8 = PLN 400

    Copper 4x16 ~ 25 PLN (net)
    copper 5x16 ~ 29 PLN (net)

    that's for comparison

    Added after 9 [minutes]:

    For all this - what kind of security do you have in your mailbox?
  • #18 9647269
    pavulon
    Level 21  
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    Quote:
    which will be connected to 7 eateries. The power I have is 25KW

    25kW is the connected or contractual capacity?

    Assuming that it is contractual, how do you want to divide this 25kW into 7 GASTRONOMIC premises?
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  • #19 9647329
    wbmike
    Level 10  
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    For now, I have borrowed a temporary box and a cable, and these premises are already connected to it. And each place will have its own sub-meter. I have a contract with a 25KW power plant.
  • #20 9647331
    Łukasz-O
    Admin of electroenergetics  
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    Where is the project ???
  • #21 9647357
    pavulon
    Level 21  
    Posts: 526
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    Quote:
    I have a contract with a 25KW power plant.

    25kW of contracted or connection capacity?

    Quote:
    For now, I have borrowed a temporary box and a cable, and these premises are already connected to it. And each place will have its own sub-meter

    But how do you want to split these 25kW
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Topic summary

✨ The discussion revolves around selecting an appropriate cable for a 50m distance to supply 25kW of power to a private box serving seven eateries, utilizing a 3-phase current. Participants suggest using YAKY cables, with recommendations for 4x16mm² or 4x25mm² cross-sections, noting that aluminum cables are more economical. Concerns about voltage drop and thermal load are addressed, with acceptable limits discussed. The importance of professional installation and compliance with standards is emphasized, alongside cost considerations for materials and installation.
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