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PEN Division, 4-Pole Surge Arrester Use in TNC-S Network: Is Image & Connection Correct?

semper fidelis1 42096 12
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  • #1 17934976
    semper fidelis1
    Level 6  
    Posts: 5
    Rate: 13
    Hello

    I have a question about the PEN division and the use of a 4-pole surge arrester in the TNC-S network.

    Is what the picture shows okay? I mean the PEN division at the input to the switchgear, then the PE to the PE bus which will be earthed to the hoop also located in the switchgear and connected to the earthing of the surge arrester.

    The overvoltage limiter is 4-way, although I do not know if it makes sense to protect N which is galvanically connected with PEN and PE, I just have it?

    TNC network with S division in my switchboard. Cable connection 4x 10mm2.
    PEN Division, 4-Pole Surge Arrester Use in TNC-S Network: Is Image & Connection Correct?
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  • #2 17935094
    mawerix123
    Level 39  
    Posts: 4143
    Help: 482
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    What is this protector :?: how did you pick it up :?:
    It's yellow-green in the lower right corner of where it will be mounted :?:
    What is this object and what does its power supply look like apart from this 4x10 cable :?:
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  • #3 17935432
    semper fidelis1
    Level 6  
    Posts: 5
    Rate: 13
    The PE rail is also originally installed in the switchgear at the bottom (I have Legrand).

    It will be a single-family house. It is the main separation, then there will be 5 pcs.

    Counter protection C25.

    The ABB B + C protector was recommended to me in an electrical store and there was nothing else on the project except that there should be a B and C protector.
  • #4 17935452
    mawerix123
    Level 39  
    Posts: 4143
    Help: 482
    Rate: 949
    You have not written how the house is powered, overhead or cable, and how long the 4x10 section is.
    The house has a lightning protection system :?:

    semper fidelis1 wrote:
    The ABB B + C protector was recommended to me in an electrical store


    Because it had been lying on the shelf for too long :D they should recommend a TN-C protector but they probably didn't have one ;)
  • #5 17935462
    semper fidelis1
    Level 6  
    Posts: 5
    Rate: 13
    That's right, they didn't have 3 poles, but what's the difference? I can't connect anything to N?

    Not exactly like the picture below.

    My power supply is earth, some 25m connection, then it is connected to the overhead line.

    There will be no lightning protection - at least for now and you will brighten me up, what will it change? The earthing hoop is connected to the earth ring around the house with the 4x32 hoop.

    PEN Division, 4-Pole Surge Arrester Use in TNC-S Network: Is Image & Connection Correct?
  • #6 17935480
    mawerix123
    Level 39  
    Posts: 4143
    Help: 482
    Rate: 949
    In my opinion, you should have an arrestor based on a magneto.

    In my opinion, this limiter is not suitable for home limp 7kA, laughs are the worst, they have about 20kA, although these are stretched values because at 8/20 where the 7kA is 10/350 and it seems it is a T1 (B) type protector and not B + C.

    With the amount you invested in ABB, you would probably buy the right one.
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  • #7 17935532
    semper fidelis1
    Level 6  
    Posts: 5
    Rate: 13
    No, you have T1 + T2 written on it, I invested less than PLN 500 in it, I do not know what would be the right one, the electrician wanted to give me some Chinese for PLN 250, I thought I would buy a better one, I did not analyze it like you because I honestly don't know much about protectors. One more thing in the project is that the ZE provides type I protection.
    Regardless of it, is the connection method correct? Should this N finally be connected to the protector or just leave it empty? If it was not, the protector is already for the division, I know there should also be N connected.
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  • #9 17935701
    semper fidelis1
    Level 6  
    Posts: 5
    Rate: 13
    Very nice article and well-written that the knowledge about when and what to use by electricians is very general, to put it mildly, most of them choose the cheap one, the customer is satisfied, the cash register agrees. I wouldn't see any further what kind of protector to use and I won't insist, but I'm not saying mine is bad anyway. However, this was not what I wanted to ask if the model is good, I could draw a square and sign it because I only mean the connections - I also had the opinion that the PE should be first to the protector and then to the PE rails, for example, but I don't know if it's the best idea.

    If someone thinks that my protector is bad, I spent money unnecessarily, I will be happy to hear what it should be - you can always replace it.
  • Helpful post
    #10 17935714
    retrofood
    VIP Meritorious for electroda.pl  
    Posts: 31317
    Help: 1140
    Rate: 4781
    Each protector is supplied with the manufacturer's instructions. So you should first check if what you bought is intended for the type of network you have, and if so, the required connection method is shown in the drawings.
  • #11 17936144
    CYRUS2
    Level 43  
    Posts: 17639
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    semper fidelis1 wrote:
    My power supply is earth, some 25m connection, then it is connected to the overhead line.
    If there is a break in the PEN in the overhead network, the receivers will also be damaged.
    The protectors will not work for this.
    semper fidelis1 wrote:
    Counter protection C25.
    Better power limiter, w or D25.
    D25 is an opportunity for short circuit selectivity
  • #12 17936156
    retrofood
    VIP Meritorious for electroda.pl  
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    CYRUS2 wrote:
    semper fidelis1 wrote:
    Counter protection C25.
    Better power limiter, w or D25.
    D25 is an opportunity for short circuit selectivity

    But it is not the author who specifies the type of security. It does in terms of attachment.
  • #13 17936252
    CYRUS2
    Level 43  
    Posts: 17639
    Help: 1221
    Rate: 3448
    retrofood wrote:
    But it is not the author who specifies the type of security. It does in terms of attachment.
    The amperage is the same.
    Power limits the same.
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Topic summary

✨ The discussion revolves around the use of a 4-pole surge arrester in a TNC-S network and the correct implementation of PEN division at the switchgear input. The user seeks clarification on the appropriateness of their setup, which includes connecting the PE to the PE bus and the earthing of the surge arrester. Various responses highlight concerns about the type of surge protector used, with suggestions for a more suitable model based on its specifications. The importance of following manufacturer instructions for installation and ensuring compatibility with the network type is emphasized. Additionally, the potential risks associated with PEN breaks in overhead networks are noted, along with the necessity of proper earthing and lightning protection considerations.
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FAQ

TL;DR: For TN‑C‑S, size your Type 1+2 SPD correctly—20 kA beats 7 kA; "this limiter is not suitable" if underrated. This FAQ clarifies PEN splitting and 4‑pole SPD connections so you wire it right. [Elektroda, mawerix123, post #17935480]

Why it matters: Picking the wrong SPD type or wiring PEN/PE/N incorrectly leaves your installation exposed and can damage equipment.

Quick facts:

  • Use a TN‑C SPD before the PEN split; use a 4‑pole 3+1 SPD after the split in TN‑C‑S. [Schneider Electric, 2018]
  • With overhead feeders or LPS, place a Type 1+2 SPD at the service entrance; verify if your DSO already provides Type 1. [ABB, 2018]
  • Keep total SPD lead length ≤ 0.5 m; each extra 0.5 m can add approx. 1 kV at 10 kA. [DEHN, 2017]
  • SPDs do not protect against a broken PEN on an overhead line; plan PEN monitoring and solid earthing. [Elektroda, CYRUS2, post #17936144]
  • Typical retail examples mentioned: combined T1+T2 SPD ~ PLN 250–500. [Elektroda, semper fidelis1, post #17935532]

Quick Facts

  • Use a TN‑C SPD before the PEN split; use a 4‑pole 3+1 SPD after the split in TN‑C‑S. [Schneider Electric, 2018]
  • With overhead feeders or LPS, place a Type 1+2 SPD at the service entrance; verify if your DSO already provides Type 1. [ABB, 2018]
  • Keep total SPD lead length ≤ 0.5 m; each extra 0.5 m can add approx. 1 kV at 10 kA. [DEHN, 2017]
  • SPDs do not protect against a broken PEN on an overhead line; plan PEN monitoring and solid earthing. [Elektroda, CYRUS2, post #17936144]
  • Typical retail examples mentioned: combined T1+T2 SPD ~ PLN 250–500. [Elektroda, semper fidelis1, post #17935532]

Is a 4‑pole SPD correct in a TN‑C‑S board after the PEN split?

Yes. After splitting PEN to PE and N, use a 4‑pole (3+1) SPD. Connect L1, L2, L3, and N to the SPD, and SPD PE to the main earthing bar. Place it near the main switch. Keep leads very short. [Schneider Electric, 2018]

Should I connect the N pole of the SPD if N is bonded to PEN at the split?

Yes. After the split, N and PE are separate conductors. The N pole is essential in a 3+1 topology to clamp neutral transients to PE. Without N, neutral overvoltages are not controlled. Before the split (TN‑C), use a TN‑C SPD. [Schneider Electric, 2018]

Is a 7 kA SPD enough for a house with overhead supply?

No. 7 kA devices are undersized at the service entrance. Typical service-entry SPDs use higher surge ratings. As one pro noted, "this limiter is not suitable." Aim for significantly higher kA capability for durability. [Elektroda, mawerix123, post #17935480]

Will an SPD protect against a broken PEN on an overhead line?

No. A broken PEN causes dangerous neutral shifts that SPDs cannot correct. Equipment can still be damaged. Use PEN monitoring and robust earthing to mitigate this risk. SPDs address surge energy, not conductor continuity. [Elektroda, CYRUS2, post #17936144]

Should PE go first to the SPD and then to the PE bar?

Connect the SPD directly to the main earthing bar with the shortest, straightest path. Then bond the PE bar to that bar. Short leads reduce added voltage; every extra 0.5 m can add approx. 1 kV at 10 kA. [DEHN, 2017]

What do the labels B, C, and T1/T2 mean (B+C vs T1+T2)?

B means Type 1. C means Type 2. A combined device marked B+C is a Type 1+2 SPD. Use combined units at service entrances to cover both lightning and switching surges. ABB and others label this clearly. [ABB, 2018]

Which SPD topology for TN‑C vs TN‑C‑S networks?

In TN‑C before the split, use a 3‑pole SPD connected to L1‑L2‑L3‑PEN. In TN‑C‑S after the split, use a 4‑pole 3+1 device connecting L1‑L2‑L3‑N to PE. Follow the device’s topology diagram. [Schneider Electric, 2018]

Do I need Type 1 if I don’t have a lightning protection system (LPS)?

Overhead feeds and service masts can conduct direct surge energy. Use a Type 1+2 at the service entrance unless the DSO already provides Type 1 upstream. If provided, a Type 2 downstream can suffice. Verify in writing. [ABB, 2018]

C25 vs D25 upstream protection—what should I use?

D‑curve can improve short‑circuit selectivity at the same current rating. However, your DSO specifies the main protective device. "It is not the author who specifies the type of security." Coordinate changes with them. [Elektroda, retrofood, post #17936156]

How should I bond the SPD to a ring earth electrode?

Bond the SPD to the main earthing bar that connects to the ring electrode. Use a short, straight conductor with adequate cross‑section (typical 16 mm² Cu). Avoid loops and sharp bends. Keep total SPD connection length ≤ 0.5 m. [DEHN, 2017]

How do I install a combined Type 1+2 SPD at the main board?

  1. Split PEN to PE and N on the main bar, bonded to the earthing electrode.
  2. Mount the 3+1 SPD near the main switch; connect L1‑L2‑L3‑N in, PE to the earthing bar.
  3. Keep all SPD leads short and straight; verify tightening torques. [ABB, 2018]

How do I confirm I’m using the right SPD and wiring?

Always follow the manufacturer’s diagrams and notes for your network type. "Each protector is supplied with the manufacturer's instructions." Check topology, conductor sizes, and placement before energizing. [Elektroda, retrofood, post #17935714]
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