Continuity when you can't isolateThe circuit can't be switched off. How do you test the cpc?

Answer c. "Can't be switched off" tells you it's a periodic, even though it doesn't say so. On initial verification the circuit would be dead anyway.

• Normally you'd use test method 1 (R1 + R2): link line and cpc at the board, then test between the line and cpc terminals at every point, e.g. every luminaire and every switch on a lighting circuit. That needs the circuit dead.
• Section 3.10 covers testing during periodics. It's short and refers back to the section 2 tests (2.6.5 onwards), but it adds some extra points.
• Where you can't isolate, don't disconnect protective and bonding conductors. Under fault conditions, exposed and extraneous-conductive-parts could rise to a dangerous voltage.
• The next paragraph gives the convenient way: the wandering lead (long lead) method. Clip the long lead to the MET, then touch the other lead on each metal accessory: switch screw heads, metal-clad sockets and luminaire casings. Be careful up steps, and cordon off the area.

GN3 · 2.6.5 continuity, test method 1 (R1 + R2) GN3 · 3.10 testing during periodic inspection GN3 · can't isolate: don't disconnect protective conductors, use the wandering / long lead · 3.10.3 · p.128