TN-C and TN-C-S system questions

21 Aug 2011
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United Kingdom
Hi, i would like to know when there is TN-C system where PEN is both neutral and earth conductor togerther. When you convert the system to TN-C-S and separate earth from neutral:

1. connect earth and N using the same bolt to PEN
2. connect earth and N separately using individual bolts to PEN

Furthermore is it worth converting TN-C to TN-C-S?
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You seem to have your wires crossed.

TNS = Terra Neut Seperate.

TNCS = Terra Neut Combined.

Cable sheath or seperate earth conductor.

To do the combined you connect both N and E together at the main board

Only do it at the first incomer point or it will impact on to RCDs.

This lowers the earth loop impedance route back to the supply.

Helps if you have a bad earth return path



TNC-S is very common in the UK, where we have a Protective Multiple Earth system in most areas which is essential to making it pretty safe. If your country works in a different way, then it would be unwise to try to apply parts of the UK method.

TNCS = Terra Neut Combined
This is wrong. Mike appears to have his wires crossed. TNC-S means Terra Neutral Combined - (then) Separate(d)

They are combined in the distribution and supply cables, but separated at the cutout, and (must) remain separate within the consumer's installation.

"you" must never combine them. Only the distribution network operator may do it, provided the supply meets the criteria.

It is incorrect, and very dangerous, for Mike to suggest a consumer or domestic electrician should connect them.
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Hi again

Anyone who asks about TT TNC TNCS must know it only applies from any building main incoming board line, back to the supply transformer. It cannot be used in most internal circuits. N currents canj find thier way into the earthing system
No volts, but tingily in the shower.

The comment on domestic electics etc is not valid, I have had internall transmision systems from 11kv down to 2,2kv all within the consumers own wiring system.

In many places, The authority supply typically came in at 33kv.

You dont mention your status, but I presume you would not be asking about tns etc if you were untrained.