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New Installation in 33m2 Old Block Apartment: Addressing 3 Phase Missing & Choosing Switchgear

szelerr 36240 19
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How do I choose between a single-phase and three-phase electrical installation for a small apartment renovation, and what do I need to do to upgrade the supply legally?

For your planned loads, a single-phase supply is likely too small if you want induction cooking and several large appliances at once; one reply estimates a 2-field hob may fit a smaller allocation, but a full induction hob can need about 9 kW, and a sensible three-phase order is around 12–15 kW [#18101368][#18100457] First ask the building manager/administration whether a 3-phase connection is possible and who owns the WLZ, then ask the energy supplier about the power increase, connection fee, and formalities, because if the WLZ cannot handle it, you may have to finance its replacement yourself [#18100457][#18100411][#18100370] In the apartment, the installation should be designed, built, and measured, with a declaration afterwards so the work is legally safe and insurance-friendly [#18100410] Between the meter and your home switchboard, the recommended minimum is a 5x6 mm² cable for 3-phase, and if the existing run is only 2-wire, it should be replaced with a 3- or 5-wire cable [#18102076][#18102124] If you stay with the current setup for now, it is still worth preparing the switchgear and wiring so you can later switch painlessly to 3-phase; one reply suggested an apartment board of about 36 modules [#18102719]
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  • #1 18100260
    szelerr
    Level 6  
    Posts: 12
    Rate: 13
    Hello, at the beginning I would like to describe the situation.
    I am starting a general renovation of a 33m2 apartment in an old block of flats. Currently, the installation is old copper 1 phase 240 v (see photo). In the middle of the apartment, the sockets are not working (electricity is there, but there is no zero or something like that). Today I will have a gentleman who will make me a working socket for construction equipment because I will demolish sowing divider.
    I would like to order someone to make a new installation and switchgear. However, I get lost in the place, what to choose and what is the process of bringing Sily to the apartment?
    I counted about 29 points at home including (TV, modem, washing machine, dishwasher, induction, extractor hood, fridge etc ..) will all this be pulled by the 240v installation ?????
    It depends for me that everything is done in accordance with the law so that I can insure my apartment.

    What to choose a 240v one phase switching station? whether 3 phases (and how to go about it)
    https://obrazki.elektroda.pl/1628621700_1565093259.jpg

    Best wishes
    New Installation in 33m2 Old Block Apartment: Addressing 3 Phase Missing & Choosing Switchgear
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    #2 18100370
    Grzegorz740
    Level 37  
    Posts: 4135
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    First, check the costs of connecting a 3-phase power supply. If you can afford it, you can get yourself a 3-phase power supply. Ask about it at the energy company. They will tell you what the connection fee is and what formalities must be met.
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  • #3 18100391
    szelerr
    Level 6  
    Posts: 12
    Rate: 13
    Grzegorz740 wrote:
    First, check the costs of connecting a 3-phase power supply. If you can afford it, you can get yourself a 3-phase power supply. Ask about it at the energy company. They will tell you what the connection fee is and what formalities must be met.



    Hello
    And it is not so that it pays ZE for it and I pay for everything from the meter?
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    #4 18100410
    kortyleski
    Level 43  
    Posts: 12262
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    Nobody will bury in offices for you. But
    szelerr wrote:
    I would like to order someone to make a new installation and switchgear.

    Your role is therefore limited to wandering around the apartment with that person and indicating where the sockets are to be, where are the points of light, where what else

    szelerr wrote:
    It depends for me that everything is done in accordance with the law so that I can insure my apartment.

    Therefore, an installation design should be made, made and measured. Then you will be safe and the insurer will have nothing to cling to.
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    #5 18100411
    kozi966
    VIP Meritorious for electroda.pl
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    szelerr wrote:
    and it is not so that he pays ZE for it, and from the meter on, I pay for everything?

    Not necessarily. Because WLZ may be owned by, for example, a housing community.
    Then the cost of 3f power supply is covered by you (bringing the appropriate cable from the main distribution board in the facility to your apartment). What could be forging in the staircase and fixing the walls after the fact.
    szelerr wrote:
    Hi people say that you do not need 240v, you can do everything and no one has to answer.

    The point here is not that someone has to pick it up, but the point is that someone has to let it operate (measurements + declaration).
    Generally, most of the devices in the residential installation will be supplied from one phase, the only question is whether the protection you can have on this one phase at most will be able to "handle" it all.
  • #6 18100440
    szelerr
    Level 6  
    Posts: 12
    Rate: 13
    kozi966 wrote:
    szelerr wrote:
    and it is not so that he pays ZE for it, and from the meter on, I pay for everything?

    Not necessarily. Because WLZ may be owned by, for example, a housing community.
    Then the cost of 3f power supply is covered by you (bringing the appropriate cable from the main distribution board in the facility to your apartment). What could be forging in the staircase and fixing the walls after the fact.
    szelerr wrote:
    Hi people say that you do not need 240v, you can do everything and no one has to answer.

    The point here is not that someone has to pick it up, but the point is that someone has to let it operate (measurements + declaration).
    Generally, most of the devices in the residential installation will be supplied from one phase, the only question is whether the protection you can have on this one phase at most will be able to "handle" it all.


    Thank you for your answer.

    "The only question is whether the security you can have at most on this one phase will be able to" bear "it all

    Can I somehow calculate it? Where can I find information about the maximum protection I can have at this stage?
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    #7 18100457
    r103
    Level 37  
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    A bit late for planning when I "start renovation" but better late than never.

    1. First of all - calculation of the required power. In your dream devices, you have an induction cooker - it can use 9 kW to work without "nerves" - you will not provide this amount of electricity "in one phase" because you have a contract for up to 5 kW and the protection will work. For all these devices, I am shooting, you need a contract for 15 kW and three phases. And that's if the heating is not on electricity

    2. Block - you must first contact the manager if it is possible to connect 3 phases and 15 kW / appropriate Internal Power Line WLZ / - after the photo I shoot that it is not.

    3. Then you go to the electricity supplier to see if he is able to supply the 15 kW - if not, then the end of the ball, if so and WLZ cannot do it - then you are either waiting for some future joint modernization - or you are taking the time and financing the construction of WLZ

    And after getting the knowledge on 1,2,3 - write to us how is it maybe someone will come up with something?
  • #8 18100478
    szelerr
    Level 6  
    Posts: 12
    Rate: 13
    r103 wrote:
    A bit late for planning when I "start renovation" but better late than never.

    1. First of all - calculation of the required power. In your dream devices, you have an induction cooker - it can use 9 kW to work without "nerves" - you will not provide this amount of electricity "in one phase" because you have a contract for up to 5 kW and the protection will work. For all these devices, I am shooting, you need a contract for 15 kW and three phases. And that's if the heating is not on electricity

    2. Block - you must first contact the manager if it is possible to connect 3 phases and 15 kW / appropriate Internal Power Line WLZ / - after the photo I shoot that it is not.

    3. Then you go to the electricity supplier to see if he is able to supply the 15 kW - if not, then the end of the ball, if so and WLZ cannot do it - then you are either waiting for some future joint modernization - or you are taking the time and financing the construction of WLZ

    And after getting the knowledge on 1,2,3 - write to us how is it maybe someone will come up with something?


    Also thank you for the opd.

    Well, that's what I put off with the renovation. I'm just going to make a bedroom.

    I was also thinking of induction only for 2 heating zones. Some of them write 240 v. Now I do not know how to respond to the electrician who was with me. He offered me switchboards above the door x things on different separate wires and guarantees that it should work without any problems, but the farther into the forest, the more I have doubts about it. The heating is not on electricity and the water is from a warmer.
  • #9 18100699
    kortyleski
    Level 43  
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    What is your power allocation in the apartment?
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    #10 18101368
    teskot
    Rest in Peace
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    Some utilities allocate power on one phase to a maximum of 5.5kW. Others give a maximum of 8.5kW (40A pre-meter protection). With this smaller allocation, in principle, only a 2-field induction hob is at stake and strictness among the household members: if a washing machine is not a dishwasher, if a full-fledged hob is used, then with a washing machine or dishwasher, then without a kettle or oven (microwave). Live is possible, but it has little to do with comfort.
    In the case of a three-phase installation, the smallest, sensible pre-meter protection is 3x20A, i.e. the ordered power at the level of 12kW.
    Induction hobs always work on one or two phases. Each can be connected to a 230V installation, but it will not necessarily be possible to use their full power. So assume that the most important receivers will be all kinds of heating devices (hob, washing machine, dishwasher, kettle, iron, coffee machine). Electronics and lighting are drawing on negligible powers today.
    Start by getting information from the community or administration about their approvals for increasing the power allocation. Perhaps it will involve the need to lay new cables between the meter and the apartment (possible hammering of walls or installation of trays or pipes). It may happen that the WLZ will not be prepared for the increased demand and will have to be replaced at its own expense. Then the consent of the energy company. After all, the electrician's statement that the residential installation is ready for connection. Good luck.
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  • #11 18102059
    szelerr
    Level 6  
    Posts: 12
    Rate: 13
    So thank you all for the answer !!
    As of today, the job looks like this:
    -electrician is making me a working socket
    - it turned out that the zero had melted in the switchboard ... yet the method for the screw screwed into the wall, everything was flying there (before there was no electricity in the middle of the apartment due to the lack of zero)
    -I will install a new board with Esami today to make it somehow fool around with the power industry, a professional will come to put a seal
    -and tomorrow I am going to the cooperative and ZE with my father because he is the owner we will deal with the issue of increasing the power and see what it will come out


    Question: is the 3-phase HL cable from the switchgear with fuses to my apartment or from my 3-phase board to the main box with fuse protection? ?
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    #12 18102076
    teskot
    Rest in Peace
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    The minimum 5x6mm? cable is to be between the meter (as I understand it in the staircase) and your home switchboard. What next depends on the energy and administration.
  • #13 18102097
    szelerr
    Level 6  
    Posts: 12
    Rate: 13
    teskot wrote:
    The minimum 5x6mm? cable is to be between the meter (as I understand it in the staircase) and your home switchboard. What next depends on the energy and administration.


    Exactly what came out after finding this wire from the meter to the apartment is 6 or thicker ... the electrician says that houses on such a thick power supply? How can I assess it myself or check what kind of cable it is? is it better to take a picture? and throw it because the gum has already crumbled on it.
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    #14 18102124
    teskot
    Rest in Peace
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    I doubt if it was more than 4mm?. It is measured normally with a caliper (after disconnecting the power supply !!!). 4mm? wire is 2.25mm in diameter, 6mm? is 2.76mm in diameter. It is definitely a two-wire cable. You have to replace it with a 3 or 5 wire (one or three phases).
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    #15 18102719
    Brivido
    Level 34  
    Posts: 2845
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    Take a photo and upload it.
    You don't have to go to the 3 phases right away, but you can always prepare the power cord. Here is a question for the manager whether he has any conditions for it, whether it can be stuck in, or in a pipe on the wall. Power supply from the meter, if it is in the stairwell, to your switchboard. If you have a meter in your apartment, it is also worth putting it outside (see the manager). Installations in the apartment are done one way or another, regardless of whether you have a 3f power supply or not, then it is a possible matter of switching in the switchgear. It is worth doing so that you can later, painlessly switch to 3F. Circuits, fuses, never too many. If it was reasonably good, it is the optimal switchgear of 36 modules for the apartment ;)
  • #16 18103709
    szelerr
    Level 6  
    Posts: 12
    Rate: 13
    This is what it looks like after changing the board. We are dealing today with an application for 15kw and 3 phases and a seal for the meter after a small renovation, unless they already have a meter for 3 phases? (I'm still getting lost in the topic)
    The electrician mentioned that the installation in the block is single-phase so there may be complications.

    Brivido - the counter is on the cage in front of the door and next to it, on the other wall, there is a cupboard as shown in the photo. with main fuse.

    New Installation in 33m2 Old Block Apartment: Addressing 3 Phase Missing & Choosing Switchgear New Installation in 33m2 Old Block Apartment: Addressing 3 Phase Missing & Choosing Switchgear New Installation in 33m2 Old Block Apartment: Addressing 3 Phase Missing & Choosing Switchgear
  • #17 18190663
    szelerr
    Level 6  
    Posts: 12
    Rate: 13
    Hello,
    Gentlemen, did anyone install Zamelem controlled blinds?
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  • #18 18190764
    szelerr
    Level 6  
    Posts: 12
    Rate: 13
    I have to pull the 3-phase cable at my own expense, fortunately it is on the ground floor and not far from the main switchboard. The tenant is in a deplorable condition burned three times. I'm pulling from the main.
  • #19 18190781
    CYRUS2
    Level 43  
    Posts: 17636
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    szelerr wrote:
    I have to pull the 3-phase cable at my own expense. On the ground floor and not far from the main switchboard, because the tenant is in bad condition, it has already burned 3 times.
    Give it to an electrician from the administration - they will not cling to the cage and design.
  • #20 18190783
    szelerr
    Level 6  
    Posts: 12
    Rate: 13
    Here I have a community + cooperative. After the phone call, it went out to them. Do the job with your electrician, seal everything and we'll take it back

Topic summary

✨ The discussion revolves around the renovation of a 33m2 apartment in an old block, focusing on the need for a new electrical installation due to the existing outdated single-phase 240V system. The user seeks advice on transitioning to a three-phase power supply, addressing issues with non-functional sockets, and ensuring compliance with legal standards for insurance purposes. Participants suggest contacting the energy company for connection costs, the importance of a proper installation design, and the need for adequate power allocation to support multiple appliances, including an induction cooker. The conversation also touches on the necessary wiring specifications and the process of upgrading the electrical system, including potential complications with the housing cooperative.
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FAQ

TL;DR: In old flats, single-phase limits are typically 5.5–8.5 kW; "Induction hobs always work on one or two phases." For comfort with induction, plan three‑phase 3x20 A (~12 kW), upgrade the WLZ if needed, and get measurements, approvals, and seals. [Elektroda, teskot, post #18101368]

Why it matters: This FAQ helps apartment renovators decide between 1‑phase vs 3‑phase, size the switchboard, and navigate approvals to stay safe and insurable.

Quick Facts

Should I stay on single‑phase 230 V or upgrade to three‑phase 400 V for a 33 m² flat?

If you want an induction hob and comfortable simultaneous use of heat appliances, upgrade to three‑phase. Single‑phase allocations often cap at 5.5–8.5 kW. Three‑phase with 3x20 A gives about 12 kW and improves diversity. You can connect many devices on one phase, but protection limits may trip. Choose three‑phase if you cook often or have multiple heat loads. [Elektroda, teskot, post #18101368]

How do I calculate the power I need?

List all heat loads first: hob, oven, kettle, washer, dishwasher, iron, coffee machine. These dominate demand; lighting and electronics are minor. If using induction, plan around 12 kW and three phases for comfort. Without electric heating, that usually covers a small flat well. Confirm the utility’s available allocation and pre‑meter protection before finalizing. [Elektroda, teskot, post #18101368]

What’s the step‑by‑step process to bring three‑phase into an apartment?

  1. Ask the building manager if the WLZ supports 3‑phase and your target power; get approval.
  2. Apply to the utility for the new allocation; confirm 3‑phase availability at your address.
  3. If the WLZ is insufficient, join a modernization or fund a compliant new feeder. [Elektroda, r103, post #18100457]

Where does the three‑phase feeder cable run?

From the meter position (often in the stairwell) to your apartment’s main switchboard. Coordinate the route and method with the manager and utility. This path sets the basis for acceptance and sealing. [Elektroda, teskot, post #18102076]

What cable size should I run between the meter and my switchboard?

Prepare a minimum 5x6 mm² copper feeder so you can switch to three‑phase without re‑wiring later. Confirm exact size with local conditions and the utility’s protection settings. Oversizing is acceptable; undersizing blocks upgrades. [Elektroda, teskot, post #18102076]

How do I check my existing feeder’s cross‑section safely?

Cut power first. Measure conductor diameter with a caliper on clean copper. 4 mm² is about 2.25 mm diameter; 6 mm² is about 2.76 mm diameter. Replace two‑wire feeders with 3‑ or 5‑core cable for safety and future 3‑phase. [Elektroda, teskot, post #18102124]

Who pays for WLZ upgrades and wall chasing in the stairwell?

The WLZ may belong to the housing community. In that case, you fund the new feeder from the main board to your flat, including wall chasing and post‑work repairs. Confirm ownership before starting. [Elektroda, kozi966, post #18100411]

Can a 230 V installation handle an induction hob plus washer/dishwasher?

It can, but with strict sequencing. With 5.5–8.5 kW single‑phase, expect limitations on simultaneous heat loads. A two‑zone hob is workable if household members avoid stacking other heaters. “Induction hobs always work on one or two phases.” [Elektroda, teskot, post #18101368]

What pre‑meter protection sizes make sense?

Typical single‑phase tops out near 40 A, about 8.5 kW ordered power. A practical three‑phase starting point is 3x20 A, about 12 kW. This supports an induction hob and normal household diversity. Ask your utility for the exact allocation. [Elektroda, teskot, post #18101368]

How big should my apartment switchboard be and how many circuits?

Plan generous space and segregation. A 36‑module board suits a small flat with room to grow. Give separate circuits to the hob, oven, dishwasher, washer, and sockets by room. “Circuits, fuses, never too many.” Label and test every circuit. [Elektroda, Brivido, post #18102719]

My sockets show voltage but “no neutral.” What’s happening and is it dangerous?

You likely have a neutral interruption or burnt connection. The OP’s neutral had melted in the old board, causing dead outlets. Replace degraded boards, remove improvised screw terminals, and test continuity and insulation. This is a safety hazard; fix before renovation continues. [Elektroda, szelerr, post #18102059]

Who approves and seals the work after I change the board?

Your electrician performs measurements and issues a declaration for the installation. The utility then seals the meter as required. As one expert put it, “someone has to let it operate (measurements + declaration).” Keep the documentation for insurance. [Elektroda, kozi966, post #18100411]

What if the building riser only supports single‑phase today?

Confirm with the manager. If the WLZ cannot handle your target, either wait for a shared modernization or fund a compliant new WLZ section. The utility must also confirm they can supply your requested power. [Elektroda, r103, post #18100457]

Can I wire now for three‑phase and upgrade later?

Yes. Run a 5‑core feeder from the meter to your board and design circuits accordingly. You can operate on single‑phase now, then switch to three‑phase in the board later with minimal disruption. [Elektroda, Brivido, post #18102719]

Can I install Zamel smart blind controllers in an old flat?

Yes, if the shutter motor and box have neutral and live present. Use a dedicated shutter controller with interlocked outputs. Fit it in a deep box or near the motor, set travel time, and pair via the app. Ensure a licensed electrician connects 230 V and verifies polarity and interlock. Follow the official wiring diagram. [Zamel SRW‑01 Manual]
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