What earthing system is in a home?

Most modern homes use TN-C-S: PEN is split into N and PE at the intake. Old houses are TN-C (no earth contact).

Can I earth to a radiator?

No — dangerous and prohibited. Use a proper earth rod or the PE conductor from the intake.

Earthing systems TN-C, TN-S, TN-C-S, TT, IT

Earthing system types per IEC 60364: TN-C, TN-S, TN-C-S, TT, IT — differences, pros, cons and applications.

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Earthing system designation

First letter — source neutral connection to earth: T (earthed) or I (isolated). Second — exposed conductive parts connection: N (to neutral) or T (separate earth).

Comparison

System	Description	Application
TN-C	Combined PEN conductor (neutral+earth in one)	Old housing stock, overhead lines
TN-S	Separate N and PE from the transformer	New construction, server rooms
TN-C-S	PEN split into N and PE at the intake	Modern homes (main system)
TT	Neutral earthed, frames via own rod	Houses with no trusted PEN
IT	Neutral isolated from earth	Medical, mining, continuous processes

Note: in TN-C an RCD is prohibited (combined PEN), and PEN must never be interrupted.

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Data is for reference. Final design decisions must follow current regulations and a qualified engineer.