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Proved dead is not finished: the other six stepsWhy a volt stick as well as your AVI?

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Everything up to here is one step of the eight. The installation being dead is what lets you do the rest safely; it is not the end of the check.

#	What you do	What you expect
3	Clamp the earthing conductor and main bonding again, now it is off	Current dropped to zero, or to an extremely small level
4	Volt stick at the MET, along the earthing conductor, along each main bonding conductor, and at the extraneous-conductive-parts	No voltage indicated
5	Disconnect the main protective bonding conductors	Nothing unusual
6	Volt stick again, same places	No voltage indicated
7	Reconnect the main protective bonding conductors	Nothing unusual
8	On a TN system, check the external earth fault loop impedance during your inspection and testing	A sensible Z_e — see below

✋Why a volt stick and not your AVI. While diverted current still has somewhere else to go, a two-pole voltage indicator will not see it. That is not a criticism of your tester — it is the physics. The book is explicit that a volt stick should be used as well. Not instead: as well.

Step 7 has a reason, and it is examinable. You put the bonding back so that insulation resistance testing can be carried out — the installation has to be connected to earth for that test. It is not tidiness. It is the next test on the sequence needing it.

Step 8 — and a number you have already met

As a rule of thumb, Z_e up to about 0.35 Ω on TN-C-S and 0.80 Ω on TN-S. A reading that is high is the signal.

✋Read that as a rule of thumb, not a pass mark. You will have met 0.35 and 0.80 elsewhere as expected maximum values. Here the book says plainly that slightly higher readings may occasionally be experienced, and that comparing against previous readings tells you more than either figure. A 0.38 Ω TN-C-S reading is a reason to look harder, not a verdict.

And the honest framing. The book says there is no simple test that shows diverted neutral current, and that these eight steps are an example of an approach for dwellings — not a universal procedure. Know them as the shape of the check, and know why each one is there.

Guidance Note 3 · Appendix D · the eight steps

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