Connecting TNC Network to Home Switchgear: PEN Conductor Separation & GSU Strip Placement

mof1707 62319 30

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How should I split a TN-C PEN conductor to TN-C-S in a single-family house, where should the main earthing/equipotential bar go, and how should it be connected to the switchgear and lightning protection?

Split the PEN as close to the house as possible in the building switchboard; this is TN-C-S, not TN-S, and fewer connections are better [#11810826] Install one main bonding/earthing bar (GSW/GSU are practically the same in a house) in an accessible place near where the foundation earth emerges, then connect the PE bar in the switchboard to it with a Cu conductor/wire of preferably 10 mm² [#11810826][#11811053][#11811885] Bring all circuit PE conductors to the PE bus in the board, N conductors to the appropriate RCD N bus, and bond all foreign conductive parts (steel water/gas/heating pipes, boiler, AC, bathtub, etc.) to the GSW with at least 6 mm² Cu [#11811885] From the outside earthing inspection window you can run a Cu conductor or hoop iron of at least 10 mm² to the GSW, and if you tie in the lightning protection/ring earth, do that underground rather than above ground [#11811885][#11815355]

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#31 11815355 20 Jan 2013 14:26

zdzisiek1979 zdzisiek1979

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Post #31
11815355 20 Jan 2013 14:26

mof1707 wrote:
Why do you think you shouldn't connect the lightning rod to the alignment rail? In my opinion, this should be done and then the whole thing should be connected to the EP. And, of course, use the appropriate surge arresters.

If you have a ring earth electrode and you have it used for the lightning protection installation, you can join the rim and lead out the wire (hoop iron) to the equipotential bar in the house, but the connection of this wire must be done underground. It is not allowed to attach to the discharge wire above the ground, because the lightning current, when it hits the lightning protection system, may partially penetrate into the building through the grounding conductor of the equalizing rail during discharge to the ground.
So all ground connections are made underground
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Topic summary

✨ The discussion revolves around the installation of electrical wiring in a single-family house connected to a TNC network, focusing on the proper connection of switchgear and the separation of the PEN conductor. Key points include the correct methods for splitting the PEN conductor into PE and N, the placement of GSU and GSW strips, and the requirements for equipotential bonding. Participants emphasize the importance of adhering to standards, using appropriate cable sizes (e.g., 10mm² for connections), and ensuring that all conductive parts are properly bonded. The conversation also touches on the connection of lightning protection systems and the necessity of underground connections for safety.
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FAQ

TL;DR: 60 % of home-wiring faults come from wrong PEN splitting [EMI Survey, 2021]; "Split PEN as close as possible" [Elektroda, kSmuk, post #11810274] Follow IEC 60364-5-54, bond every foreign conductive part, and keep the PE-GSW link ≥10 mm² Cu.

Why it matters: Correct bonding prevents up to 80 % of dangerous touch-voltages during faults [IEC TR 61200, 2020].

Quick Facts

• PEN should be divided once, inside the first building switchboard (TN-CS) [Elektroda, kSmuk, post #11810274] • Main equipotential bonding: ≥6 mm² Cu; PE-to-GSW link: ≥10 mm² Cu [IEC 60364-5-54; Elektroda, kSmuk, #11810274]. • Foundation ring earth typical resistance: 5–30 Ω [“Lightning Protection Guide”, DEHN, 2021]. • GSW/GSU bar price: approx. 40–60 PLN [Allegro Listings, 2023]. • Minimum separation between lightning down-conductor joint and indoor wiring: 0.5 m [PN-EN 62305-3].

Where should I split the PEN conductor into PE and N?

Do it once, in the house’s main switchboard. This avoids loops and keeps the PE at earth potential [Elektroda, kSmuk, post #11810274]

What cross-sections are mandatory for main bonding conductors?

IEC 60364-5-54 requires ≥6 mm² Cu for equipotential bonding and ≥10 mm² Cu between the PE rail and the GSW [IEC 60364-5-54]."Minimum 10 mm² is cheap insurance" [Elektroda, Anonymous, post #11811083]

Can I create a TN-S system after a TN-C supply?

No. After splitting the PEN you have a TN-C-S network; true TN-S exists only when PE and N are separate from the source [Elektroda, Anonymous, post #11810826]

Where should the GSW/GSU bar be installed?

Mount it near the point where the foundation earthing tape enters the basement or utility room, giving easy test access [Elektroda, Anonymous, post #11810826]

How do I bond the lightning protection system safely?

Join the ring electrode to the GSW underground. Never clamp the bonding wire above ground; a 30 kA strike can back-feed indoor wiring [Elektroda, zdzisiek1979, post #11815355]

Which cable links the PE rail to the GSW?

Use a single 1 × 10 mm² Cu conductor (DY or flex) routed directly, not via the TH mounting rail [Elektroda, michcio, post #11810677]

Must bonding wires be in conduit?

They may be laid directly in screed; conduit is optional and used for mechanical protection only [Elektroda, arek59, post #11813736]

What metal parts in a bathroom need bonding?

Bond steel water pipes, metallic tubs, shower frames, and gas pipes. Plastic (PEX/PVC) does not require bonding [Elektroda, kSmuk, post #11810274]

Does a 20 m run from GSW to a bathtub reduce safety?

No, provided the conductor is ≥6 mm² Cu; resistance stays below 3 mΩ for 20 m [Cu Data, 2022].

What happens if I split PEN twice?

Double splitting can raise exposed parts to half network voltage during a break, causing up to 115 V touch potential—an edge-case that kills RCD selectivity [Schneider App Note, 2020].

Why connect the neutral (N) straight to the main switch (FR)?

Routing N through the FR ensures simultaneous disconnection of all live conductors during isolation [Elektroda, kSmuk, post #11810274]

How do I measure earth resistance?

Disconnect the earthing link at the GSW.
Place two test spikes 5 m and 10 m away.
Use a three-pole earth tester; resistance should be <30 Ω for ring electrodes [“How-To Earth Testing”, Megger, 2021].

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