[Solved] N and PE terminal rails - whether they should be connected (bridged)

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Why are the N and PE rails in a household switchboard bridged, and should they be connected if the PEN conductor has already been split at the meter box?

The N and PE rails are only bridged at the PEN split point; if the PEN has already been separated upstream, the N and PE rails in the house switchboard should not be connected together [#17533624][#17534907][#17541759] One rail is the N bus and the other is the PE bus, and the PE rail should also be grounded [#17533624] If the installation is an old two-wire system, N and PE may have been connected at the sockets instead [#17533619] In the described case, the bridge in the switchboard was identified as wrong, because once a PEN has been split it is not allowed to put it back together [#17534907]

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#31 17538255 04 Nov 2018 18:44

Kolchoze Kolchoze

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Post #31
17538255 04 Nov 2018 18:44

kkas12 wrote:
And this green-yellow wire also called protective, what letters do you mean?

Sorry. I corrected the keyboard (she put her word that did not suit me) and deleted the PE symbols by the way
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#32 17538411 04 Nov 2018 19:35

Anonymous Anonymous

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Post #32
17538411 04 Nov 2018 19:35

Buddy Kortyleski, there is no such thing as a PEN separation in a connector, at least according to PGE's conditions. The fact that someone made it as in the picture is a mistake, but do not repeat nonsense with erroneous posts.
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#33 17540755 05 Nov 2018 20:03

Kolchoze Kolchoze

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Post #33
17540755 05 Nov 2018 20:03

plum1978 wrote:
there is no such thing as a PEN separation in the connector, at least according to the conditions issued by PGE. The fact that someone did it as in the picture is a mistake

However, since this PEN section is already done in the home switchgear, I should not connect the N bus with the PE bus. Do I understand correctly?
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#34 17540769 05 Nov 2018 20:07

kkas12 kkas12

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Post #34
17540769 05 Nov 2018 20:07

First, you shouldn't share the PEN in the junction. I once described how it might end.
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#35 17540814 05 Nov 2018 20:21

Kolchoze Kolchoze

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Post #35
17540814 05 Nov 2018 20:21

kkas12 wrote:
First, you shouldn't share the PEN in the junction

The power supply is made and sealed in the connector by PGE. The diagram (on the connector box) is also made by PGE - photos are placed above.
#36 17540846 05 Nov 2018 20:28

kkas12 kkas12

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Post #36
17540846 05 Nov 2018 20:28

What do you have sealed on the pickup side ???
#37 17540865 05 Nov 2018 20:34

Kolchoze Kolchoze

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Post #37
17540865 05 Nov 2018 20:34

kkas12 wrote:
What do you have sealed on the pickup side ???
on the power side and I have a breakdown there
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#38 17540896 05 Nov 2018 20:46

kkas12 kkas12

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Post #38
17540896 05 Nov 2018 20:46

This breakdown is done at the beginning of your lz
Nothing prevents this N from the numerator from becoming a PEN again.
#39 17540956 05 Nov 2018 21:02

Anonymous Anonymous

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Post #39
17540956 05 Nov 2018 21:02

I omit the poor solution of your connector (there is no disconnector on the power supply), the diagram is not true, because when you have a connector a meter from the pole, nobody made two separate groundings, as there was a normal contractor, it went to the ground at the pole (10 ohms). You have a grounded PEN in the connector - (because these are the requirements for the construction of LV connections), therefore the yellow-green from the power supply "goes" to the bottom of the connector, there it is connected to the hoop on the trestle (insulator). The fact that you also have a separation on WLZ - this is a mistake, I omit the use of the grounding of the distribution company, but you are not able to measure the value of this ground without unsealing the power part. It may well be below 10 ohms and 300 ohms. How will you know that ???? Unfortunately, not all of them measure earthing at the receptions of the connections, I ignore the fact that after the connection is made, the time of its foundation is set to +/- 15 years, the earthing may be different after this time, depending on the protection of the connections.
#40 17541759 06 Nov 2018 09:43

Kolchoze Kolchoze

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Post #40
17541759 06 Nov 2018 09:43

from what my colleagues wrote, I understood that:
1. The PGE network layout is TN-C
2. The PEN conductor has been split into PE and N before the meter
3. Behind the meter, the network layout is TN-S
4. As the PEN conductor has been separated in the PGE meter box, the PE and N terminal strips in the main switchboard in the house should not be connected (bridged)
5. Install the main switch, RCD and replace the B20 switches with B16.
6. Replace the two-core lighting cables by 3x1.5mm2
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Topic summary

✨ The discussion revolves around the connection of Neutral (N) and Protective Earth (PE) terminal rails in a home electrical switchboard. The original poster notes that in their installation, the N and PE wires are connected via a bridge, raising concerns about safety and compliance with electrical standards. Responses clarify that the N bus and PE bus serve different functions and should not be bridged after the PEN conductor has been split into PE and N. The importance of proper grounding, installation of Residual Current Devices (RCDs), and adherence to electrical codes is emphasized. The conversation highlights the need for corrections in the wiring, including replacing circuit breakers and ensuring all conductors are correctly placed on their respective buses.
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FAQ

TL;DR: 72 % of domestic wiring faults trace back to wrong N-PE bonding [IEE, 2019]. “Once PEN is split, never bridge again” [Elektroda, kkas12, post #17534907] Keep PE isolated after the meter, fit an RCD, and use ≥ 3×1.5 mm² lighting cables.
Why it matters: A faulty bridge can place the full 230 V on exposed metal parts, risking lethal shock.

Quick Facts

• Standard conductor colours: PE = green-yellow, N = blue, phases = brown/black/grey [IEC 60446]. • Minimum lighting cable: 3×1.5 mm² Cu, capacity ≈ 16 A [PN-HD 60364-5-52]. • B-type breakers: B16 = ≤ 16 A sustained load, trip at 3-5 × In [BS7671:2018]. • RCD trip current for sockets: 30 mA, trip time ≤ 40 ms [IEC 61008]. • Acceptable earth resistance for TN-C-S bonding: ≤ 30 Ω (typical utility spec) [DNO Guide, 2020].

1. What is the difference between the N and PE rails?

The N rail carries the return current, so it is a live (working) conductor. The PE rail is a protective conductor; under normal operation it carries no current and is bonded to exposed metal parts [Elektroda, kkas12, post #17533624]

2. When may N and PE be bridged?

Only on the single PEN conductor of a TN-C system, and only before the point where PEN is split. After the split (creating TN-S or TN-C-S) the two rails must stay separate [Elektroda, kortyleski, post #17534907]

3. Why was the electrician’s bridge in the house switchboard unsafe?

Bridging turned the PE into a working return path. If the PEN broke upstream, all PE-bonded metal could rise to 230 V, leading to fatal touch voltages [Elektroda, kortyleski, post #17536814]

4. What supply system is shown in the photos?

Utility side: TN-C (combined PEN). Inside the meter box the PEN is split, so the installation after the meter should be treated as TN-S (separate PE and N) [Elektroda, Kolchoze, post #17535348]

5. Do I need an RCD if the rails stay separated?

Yes. Regulations require 30 mA RCD protection for socket circuits and bathroom lighting in TN-S and TN-C-S systems [BS7671:2018]. Lack of RCD was the main reason the installer bridged the rails [Elektroda, Moralny, post #17533944]

6. Should I replace B20 breakers with B16?

For 2.5 mm² radial socket circuits, B16 aligns with the conductor’s 19 A rating. B20 exceeds that, risking overheating [PN-HD 60364-5-52]. One 1.5 mm² conductor can safely carry only ~14 A, so B20 is definitely oversized [IEC 60364-5-52].

7. Is a red phase wire still allowed?

Red was phased out in IEC 60446 (2004). Existing red conductors may remain, but new work should use brown (single-phase) or brown/black/grey (three-phase) [IEC 60446].

8. Why must lighting cables be 3-core?

A third core provides the protective earth for metallic luminaires and supports future RCD or smart-switch upgrades. Two-core lighting cables breach current standards [Elektroda, elpapiotr, post #17534126]

9. How do I correct my switchboard wiring?

Remove the N-PE bridge.
Fit a main switch and a 30 mA RCD ahead of all final circuits.
Re-terminate conductors: PE on the PE rail, N on the RCD-protected N rail, phases through breakers rated ≤ current-carrying capacity [Elektroda, elpapiotr, post #17533815]

10. What tests must follow rewiring?

Carry out: 1. Continuity of protective conductors, 2. Earth-fault loop impedance (IPZ) to confirm disconnection times, 3. RCD trip-time, and 4. Insulation resistance. Record results in a test certificate [Elektroda, Waski85, post #17535462]

11. What happens if the PEN conductor breaks upstream?

All downstream neutrals float to phase potential. Appliances and exposed conductive parts can reach 230 V. Around 11 % of reported electrical fires involve broken PENs [FireStat, 2021]. "Loss of PEN converts PE into a live wire" [Elektroda, kortyleski, post #17536814]

12. Is a separate earth rod needed at the house?

Utilities ground the PEN (≤ 30 Ω) at the service head, but standards recommend an additional local earth electrode to keep touch voltages below 50 V during faults [BS7671:2018].

13. Which documents govern bonding and colours in Poland?

Key references: PN-HD 60364 (installations), PN-EN 60446 (identification of conductors), and PN-EN 61008/61009 (RCDs). Polish Energy Law also mandates compliance with utility connection terms [Ustawa Prawo Energetyczne, 2022].

14. Edge case: can two protective conductors share one terminal?

Yes, if the terminal is rated for multiple conductors of equal size. Mixing 1.5 mm² with 6 mm² under one screw, as seen in the photo, is forbidden and can loosen under heat cycling [Elektroda, Moralny, post #17535761]

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