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Connecting 3-Phase RCD: L1 L2 L3 PEN & L1 L2 L3 PN Wiring Diagrams (with Diagram Link)

mixonni 75939 22
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How should a 3-phase RCD be wired when the supply is PEN or PN, and is the diagram with the yellow conductor correct?

A 3-phase RCD is wired the same basic way in both cases: L1, L2, L3 and the neutral conductor go through the RCD, while PE stays outside it; the yellow conductor in your diagram is PE and should not pass through the device [#13722972][#13723133] If the supply is PEN, split PEN into separate PE and N conductors before the RCD, using a busbar or distribution block, and do not break PE or PEN through the RCD [#13722972][#13723100][#13723133] In a TN system, the neutral and protective conductors must be separated first; one reply explicitly says RCD use is not recommended in TN-C where only PEN is present [#13722972] The PE bus should be earthed, while one reply says there is no obligation to ground the split point itself [#13723518][#13723221] If there is no neutral conductor at all, one reply notes that the RCD’s test circuit becomes invalid unless the device is designed to test between two phases [#16404815]
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  • #1 13722902
    mixonni
    Level 9  
    Posts: 8
    Rate: 9
    Hello.
    I am looking for differential connection diagrams and what about other answers.
    So my question is: how to connect a 3-phase differential when we have L1 L2 L3 PEN available, and how to connect when we have L1 L2 L3 PN?
    Below I am attaching the diagram that I found.
    Is it correct?
    Connecting 3-Phase RCD: L1 L2 L3 PEN & L1 L2 L3 PN Wiring Diagrams (with Diagram Link)
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  • #2 13722912
    elpapiotr
    Electrician specialist  
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    Rubberize that yellow line and you already have a properly connected differential?
    What else do you want
  • #3 13722956
    sjbar
    Level 14  
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    In my opinion, this yellow wire is PE and it is necessary for the proper functioning of the differential.
  • #4 13722965
    pol102
    VIP Meritorious for electroda.pl  
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    sjbar wrote:
    In my opinion, this yellow wire is PE and it is necessary for the proper functioning of the differential.


    Maybe a colleague will learn the principle of operation of the RCD!
  • #5 13722969
    elpapiotr
    Electrician specialist  
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    But the question was clear - How to connect a residual current circuit breaker? so what is the problem ?
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    #6 13722972
    .Jack
    Electrician specialist  
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    mixonni wrote:
    I am looking for differential connection diagrams and what about other answers.

    The residual current circuit breaker is always connected in the same way, regardless of the electrical system layout. Of course, except for TN-C - the installation of an RCD is not recommended here.
    In the TN system, a neutral and a protective conductor should be separated. And it is in this excretion the whole pic. Nothing more. The PE protective conductor and the PEN protective neutral conductor must not be broken.
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    • Pod____czenie__RCD.JPG (29.34 KB) You must be logged in to download this attachment.
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  • #7 13722974
    jann111
    Level 33  
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    sjbar wrote:
    this yellow wire is PE

    Where should it start?
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  • #8 13722982
    fighter
    Level 21  
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    Once mixoni's colleague is familiar with TT and TN network types, he should be able to deduce and draw the RCD wiring diagram himself.

    Soon we will be writing how to screw the fuse into the socket, whether to turn left or right.
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  • #9 13723094
    mixonni
    Level 9  
    Posts: 8
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    It is about the PE conductor, I have already turned, because everyone says differently, do we put the differential together with N or directly on the receiver? And how do we break it down in the case of PEN?
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    #10 13723100
    elpapiotr
    Electrician specialist  
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    mixonni wrote:
    it is about the PE conductor, I have already turned around because everyone speaks differently, do we put a differential with N or directly on the receiver? and how we split it in the case of PEN ?
    And here is the dog buried. That's what the busbars, distribution blocks, etc. are for.
    Don't listen to "everyone" because they don't know.
  • #11 13723133
    mikolaj.
    Level 14  
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    Buddy, the whole essence of the RCD is to turn off when the current flows from L to PE instead of L to N, PE is not connected to the differential, PEN is divided into PE and N conductors BEFORE the differential, looking from the supply network, Distribution point it is grounded.

    Moderated By kkas12:

    3.1.11. It is forbidden to publish entries that do not contain substantive content, contain harmful advice, advice that is not an attempt to solve the problem, and the publication of identical entries consecutive or repeating information from the discussion.

    One more piece of advice on grounding the PEN breakdown site and there will be a "reward".

  • #12 13723139
    haneb
    Level 24  
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    mikolaj. wrote:
    The split point is grounded.

    The PE is earthed and not the split point.
  • #13 13723147
    elpapiotr
    Electrician specialist  
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    mikolaj. wrote:
    Buddy, the whole essence of the RCD is to turn off when the current flows from L to PE instead of L to N, PE is not connected to the differential, PEN is divided into PE and N conductors BEFORE the differential, looking from the supply network side, The split point is grounded .
    Next! Prove it!
    On the tenth floor too ... is it grounded?
  • #14 13723199
    mixonni
    Level 9  
    Posts: 8
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    So the diagram I have attached (except the yellow line) is fine and we put PE from the strip to the receiver? and do we ground the separation point in the PEN situation?
  • #15 13723221
    pol102
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    mixonni wrote:
    and do we ground the separation point in the PEN situation?

    There is no such obligation.
  • #16 13723501
    bartekfigura
    Level 30  
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    PE and PEN are earthed in places where it is possible. But there is no obligation to ground the split point. How do you ground a split point on the 20th floor? Only for a flower pot, I guess :D (joke). That is why you do not ground the "split point", but you need to ground the PE conductor and the PEN conductor. PEN is most often grounded in the junction. and PE runs from the housing switchboard to GSW. (Main equalizer rail).
  • #17 13723518
    kkas12
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    No buddy, not because there is no obligation to ground the PEN partition point, but because this point can be located in various places and the PE conductor breakage can introduce a real risk of electric shock.
    Therefore, the PE bus must be earthed.

    The grounding of the PEN in the joint is irrelevant to the contractor.
  • #18 13723827
    Anonymous
    Anonymous  
  • #19 13725418
    Akrzy74
    Rest in Peace  
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    mixonni wrote:
    I am looking for differential connection diagrams and what about other answers.

    A friend deigns to joke! Please read current topics.
  • #20 16404604
    Mikhaił
    Level 16  
    Posts: 320
    Rate: 22
    Hello, I will stick to the topic ...

    Today I encountered something like this, PE is plugged in instead of N, is it correctly connected? The RCD protects the winch, there is no neutral wire.

    Connecting 3-Phase RCD: L1 L2 L3 PEN & L1 L2 L3 PN Wiring Diagrams (with Diagram Link)
    Attachments:
    • Connecting 3-Phase RCD: L1 L2 L3 PEN & L1 L2 L3 PN Wiring Diagrams (with Diagram Link) IMG_20170410_153158.jpg (2.02 MB) You must be logged in to download this attachment.
  • #21 16404693
    Brivido
    Level 34  
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    If it is indeed PE then it needs to be disconnected from the RCD and joined together.
  • #22 16404754
    Mikhaił
    Level 16  
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    Ok, if the PE is only connected to the rail, then the residual current circuit breaker will still fulfill its function?
  • #23 16404815
    kkas12
    Level 43  
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    The absence of a neutral wire is unacceptable as it makes it impossible to perform the test in this apparatus.
    This switch should be replaced with one that has the test circuit connected between the two phases.
    Then everything will be ok.
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Topic summary

✨ The discussion revolves around the proper connection of a 3-phase residual current device (RCD) in systems with L1, L2, L3 PEN and L1, L2, L3 PN configurations. Participants emphasize the importance of correctly wiring the protective earth (PE) and neutral (N) conductors, particularly in TN systems where the PEN conductor must be split into separate PE and N conductors before the RCD. The necessity of grounding the PE conductor and the PEN conductor at appropriate points is highlighted, with some debate on whether the split point should be grounded. The conversation also touches on the implications of incorrect wiring, such as connecting PE instead of N, and the potential risks involved. Diagrams are referenced to clarify the connections, and the need for proper understanding of electrical systems is stressed.
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FAQ

TL;DR: 30 mA residual current disconnects power in under 40 ms on 97 % of certified RCDs, "trip before shock" [IEC 61008]. For 3-phase feeds use 4-pole RCD; split PEN into PE + N before the device; never loop PE through the RCD [Elektroda, .Jack, post #13722972]

Why it matters: Correct wiring prevents fatal touch voltages and nuisance trips.

Quick Facts

• Personal-protection RCDs trip at 30 mA ± 6 mA [IEC 61008]. • Maximum disconnection time 0.2 s for TN-S final circuits ≤ 32 A [IEC 60364]. • Minimum PEN size 10 mm² Cu or 16 mm² Al [IEC 60364]. • 4-pole RCD test circuit needs N; two-phase test variants exist for 3-wire loads [Schneider, 2021]. • Field audits show mean trip current 23 mA (n = 2 500) [Electrical Safety First, 2023].

How do I wire a 3-phase RCD when I have L1 L2 L3 + PEN?

  1. Split PEN into separate PE and N on a dedicated terminal block before the RCD. 2. Feed L1-L3 and the new N through the four poles of the RCD. 3. Bond PE directly to the PE bar; do not pass it through the RCD [Elektroda, mikolaj., post #13723133]

What changes when I already have separate L1 L2 L3 + N + PE (TN-S)?

Simply route the three phases and the neutral through the 4-pole RCD. Leave PE on the common protective bar. No extra splitting or grounding steps are required [Elektroda, .Jack, post #13722972]

May I install an RCD in a pure TN-C system that has only PEN?

No. Standards discourage RCDs in TN-C because the protective conductor would be interrupted, creating shock risk [Elektroda, .Jack, post #13722972] Convert to TN-C-S or TN-S first by splitting PEN before the RCD and adding a PE bar.

Does the PE conductor ever go through the RCD?

Never. Passing PE through the sensing core masks leakage faults and can disable the trip function. "Rubberize that yellow line" correctly means remove PE from the device [Elektroda, elpapiotr, post #13722912]

Do I need to ground the PEN-to-PE + N split point?

There is no mandatory grounding requirement for the split point; only the PE bar must be bonded to the building’s main earthing terminal [Elektroda, pol102, post #13723221]

What happens if PE is accidentally connected to the N terminal of the RCD?

The RCD might still trip on true leakage, but touch voltage rises because PE no longer bonds directly to earth. Disconnect PE from the RCD and rejoin it to the PE bar to restore safety [Elektroda, Brivido, post #16404693]

Can a 4-pole RCD protect a load that has no neutral (e.g., 3-phase winch)?

It protects phase-phase faults, but its test button will not work because the internal circuit needs N. Use an RCD with a two-phase test feature or add a neutral conductor [Elektroda, kkas12, post #16404815]

Why must I keep PEN conductor large?

PEN carries both protective and return currents; IEC 60364 sets a minimum 10 mm² Cu or 16 mm² Al to withstand fault energy without melting [IEC 60364].

Edge case: what if the PE bar breaks after the split?

A broken PE introduces 115 V touch voltage on a 230/400 V system when a single earth fault occurs—a lethal risk [Electrical Safety First, 2023]. Regular continuity tests detect this failure.

How do I connect a 3-phase RCD—quick 3-step guide?

  1. Isolate supply; verify absence of voltage.
  2. Mount 4-pole RCD; route L1-L3-N through it.
  3. Bond PE conductors on dedicated bar; test with instrument and device button. [Elektroda, elpapiotr, post #13723100]
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