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3x2.5 Cable Capacity: Can It Handle 3kW or 4kW for Garage Workshop Tools?

fussil 35202 11
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  • #1 19063195
    fussil
    Level 9  
    Posts: 16
    Rate: 3
    Hi,

    I am in the process of installing electricity in the garage and initially bought 2kW from the distributor, but I found that I may sometimes miss it. I'm planning to write a power boost application, but I have two questions:

    1. Take 3kW or 4kW. Workshop tools will be used, such as: drills, grinders, vacuum cleaner, impact wrenches, occasionally a welding machine, etc.

    2. I have a 3x2.5 cable, will it be enough for 4kW?
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  • #2 19063211
    moze-byc
    Level 29  
    Posts: 1001
    Help: 133
    Rate: 140
    fussil wrote:
    1. Take 3kW or 4kW. Workshop tools will be used, such as: drills, grinders, vacuum cleaner, impact wrenches, occasionally a welding machine, etc.

    Take as much power as the tools you will be comfortable working with at once. i.e. count the lighting, let's say a vacuum cleaner with some power tool, more probably won't be needed. Means 4kW may be missing,
    fussil wrote:
    2. I have a 3x2.5 cable, will it be enough for 4kW?

    It depends on where you want to put it and what the layout of the network is. If the system is TN-C and you want to use it as a main switch and connect the meter switchgear with protections, you absolutely cannot use it - minimum 10mm sq because this is the minimum cross-section of the PEN conductor.
    In addition, the issues of voltage drop (how long is the cable), arrangement method (cooling issue), short-circuit loop impedance (so that the short-circuit protections work in the event of a short-circuit and the cables do not ignite.

    In general, describe the installation in detail with the distances and plan - the number and type of circuits, etc. Everything you know.
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  • #3 19063231
    fussil
    Level 9  
    Posts: 16
    Rate: 3
    The cable has a length of about 22 meters and is laid ~60 cm underground in a blue corrugated conduit. On one side connected to the meter box and on the other side in the garage to the 2x20A fuse box
  • #4 19063240
    moze-byc
    Level 29  
    Posts: 1001
    Help: 133
    Rate: 140
    Do you have the possibility to see how the cable is connected in the box with meters? A photo of some grilles, if any, which will allow you to see exactly what it looks like? The documentation of the switching station is best for this, the contract with the energy supplier in which the network layout is given?
  • #5 19063243
    Pan.Kropa
    Level 35  
    Posts: 3919
    Help: 246
    Rate: 1120
    What is the value of your pre-meter collateral? And what fare?
  • #6 19063342
    fussil
    Level 9  
    Posts: 16
    Rate: 3
    Unfortunately, I can't see the connection of the cable or the grilles because I don't have the meter attached yet. It will most likely be installed tomorrow.
    Connection power 2kW, voltage 0.4kV
    classified in group V
    Pre-meter protection - 10A in the cable-measurement connector
    power factor tg < 0.4
    The low-voltage network operates in the TN-C system
  • #7 19063349
    Pan.Kropa
    Level 35  
    Posts: 3919
    Help: 246
    Rate: 1120
    Well, with 10A fuse you can draw about 2300 watts.
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  • #8 19063359
    fussil
    Level 9  
    Posts: 16
    Rate: 3
    That's why I want to increase it to 4kW and the question is whether the cable will last that long
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  • #9 19063362
    moze-byc
    Level 29  
    Posts: 1001
    Help: 133
    Rate: 140
    fussil wrote:
    the low-voltage network operates in the TN-C system

    In this case, I do not know who pulled 3 * 2.5mm there, but he did it wrong. Well, it couldn't possibly get any worse. The cable to be removed (you will use it in the garage) and there is 2x10mm and a section plus an equipotential ground in the garage, possibly the same with 4x10mm.

    Added after 3 [minutes]:

    fussil wrote:
    That's why I want to increase it to 4kW and the question is whether the cable will last that long

    It won't hold up, and it's not suitable for use as a WLZ. According to the standards, the PEN cable must be at least 10mm sq and it does not matter whether you will consume 20kW or 2kW with it. It's got to be the end.
    I edited. I am asking for more subdued statements so that no one has to correct them. {TM]
  • #10 19063632
    adwlodar
    Level 28  
    Posts: 1067
    Help: 111
    Rate: 245
    moze-byc wrote:
    for positioning is 2x10mm

    I'd rather give it to myself:
    1. Moderately available cable, i.e. YKY 2x10, moreover, the price in the 4x10 network is ridiculously low compared to 2x10
    2. You will need a 3 phase device soon and more costs with cable replacement / digging etc.

    With the replacement of the cable, I advise you to wait for the conditions from ZE anyway. We can assume the division of PEN in the garage, and if the "state within the state" (ZE) does, we have no influence on it ...

    Where are you from Author? What operator?
  • #11 19063644
    moze-byc
    Level 29  
    Posts: 1001
    Help: 133
    Rate: 140
    adwlodar wrote:
    the price on the 4x10 network is ridiculously small compared to 2x10

    Tell that to someone who preferred to buy a 2.5mm :)
    adwlodar wrote:
    With the replacement of the cable, I advise you to wait for the conditions from ZE anyway. We can assume the division of PEN in the garage, and if the "state within the state" (ZE) does, we have no influence on it ...

    The division will have to be in the garage, I don't see any other option. But we will see.
  • #12 19063731
    Ktoś_tam
    Level 40  
    Posts: 5202
    Help: 502
    Rate: 2795
    fussil wrote:
    On one side connected to the meter box and on the other side in the garage to the 2x20A fuse box

    ... (3 posts further)

    pre-meter protection - 10A in the cable-measurement connector

    Do you see the logic here? What is your garage security job? I omit the fact of pre-counter protection, but such a nominal one cannot be found in the garage.

    Say I'm not mistaken, in the ground you have a "cable" in white outer insulation?

    I don't know who did it, but don't let that someone play electric because it can do more harm than good.
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Topic summary

✨ The discussion revolves around the capacity of a 3x2.5 mm² cable to handle power requirements for garage workshop tools, specifically whether it can support 3kW or 4kW. The user initially planned for 2kW but is considering an upgrade due to potential higher usage. Responses highlight the importance of considering the total load from various tools, including drills, grinders, and welding machines. Concerns are raised about the adequacy of the 3x2.5 mm² cable, especially given its length of 22 meters and installation conditions. Experts suggest that a minimum cable size of 10 mm² is necessary for safety and compliance with standards, particularly in a TN-C system. Recommendations include replacing the existing cable with a larger gauge to accommodate future power needs and ensure safety.
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FAQ

TL;DR: 10 mm² minimum PEN in TN‑C; "It won't hold up" for 3×2.5 as a supply. For 3–4 kW garage tools, replace the feed with 2×10 or 4×10 mm² and reuse 3×2.5 inside. [Elektroda, moze-byc, post #19063362] Why it matters: This FAQ guides homeowners setting up a TN‑C garage workshop on choosing 3 vs 4 kW and safe cable sizing.

Quick Facts

Can a 3×2.5 mm² cable feed 3–4 kW to my garage on TN‑C?

No. In TN‑C, the supply conductor is PEN and must be at least 10 mm². A 3×2.5 mm² cable cannot serve as the main supply (WLZ). Remove that run and install 2×10 or 4×10 mm². Repurpose the 3×2.5 mm² for internal circuits only. “It won’t hold up” for WLZ use. [Elektroda, moze-byc, post #19063362]

How much power can I draw with a 10 A pre‑meter fuse?

About 2,300 W at 230 V. That’s your ceiling until the operator upgrades your contractual power and upstream fuse. For sustained workshop use, request a higher limit or a three‑phase connection. [Elektroda, Pan.Kropa, post #19063349]

Is 3 kW or 4 kW enough for drills, grinder, vacuum, and an occasional welder?

Budget power for what runs simultaneously. Count lighting plus a vacuum and one power tool. “Take as much power as the tools you will be comfortable working with at once.” Even 4 kW can be tight depending on combinations. [Elektroda, moze-byc, post #19063211]

What is the minimum PEN cross‑section and why?

PEN must be at least 10 mm² by standard, independent of whether you draw 2 kW or 20 kW. This maintains a robust fault path and safe operation. “According to the standards, the PEN cable must be at least 10mm sq.” [Elektroda, moze-byc, post #19063362]

Which cable type should I install for the garage supply?

Use YKY 2×10 mm² for single‑phase TN‑C supplies, or YKY 4×10 mm² to future‑proof for three‑phase. 4×10 mm² is readily available and the price difference is small versus 2×10 mm². [Elektroda, adwlodar, post #19063632]

Where should I split PEN into PE and N?

Plan the PEN split in the garage distribution board. Provide separate PE and N bars and bonding as required. “The division will have to be in the garage.” Coordinate with the operator’s conditions before finalizing. [Elektroda, moze-byc, post #19063644]

Should I replace the already buried 3×2.5 mm²?

Yes, for use as the supply it is incorrect. Remove it as WLZ and reuse the cable inside the garage for branch circuits. Replace the supply with 2×10 or 4×10 mm² per TN‑C requirements. [Elektroda, moze-byc, post #19063362]

How do I request a power increase without rework?

Follow this quick plan:
  1. Request connection conditions from your operator (ZE) before digging or buying cable.
  2. Select YKY 4×10 mm² if you may want three‑phase later.
  3. Implement the PEN division and cable routing once ZE’s conditions arrive. [Elektroda, adwlodar, post #19063632]

Is three‑phase worth considering for a garage workshop?

Yes. You may soon add a three‑phase device; replacing the cable later means new digging and costs. Running 4×10 mm² now avoids rework, and the cost difference versus 2×10 mm² is small. [Elektroda, adwlodar, post #19063632]

What checks ensure a safe underground run?

Evaluate voltage drop, installation method (cooling), and short‑circuit loop impedance. “So that the short‑circuit protections work and the cables do not ignite.” An undersized or poorly cooled run risks failure to trip and overheating. [Elektroda, moze-byc, post #19063211]

Is a white‑sheathed cable in the ground a red flag?

Yes. A white jacket underground suggests an indoor cable was buried. Pause the job, verify the exact cable type, and reassess the installer’s competence. “Don’t let that someone play electric.” [Elektroda, Ktoś_tam, post #19063731]

Does a 2×20 A garage subpanel make sense with a 10 A upstream fuse?

No. That coordination is questionable, since the upstream 10 A protection would trip first. Re‑evaluate downstream ratings so they align with the supply and operator limits. [Elektroda, Ktoś_tam, post #19063731]

What should I document from the meter box before deciding?

Photograph the metering box, labels, and any busbar arrangements. Obtain switching‑station documentation and the utility contract showing network type and fuse values. This confirms TN‑C details and how to size and connect your new cable. [Elektroda, moze-byc, post #19063240]
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