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Bonding continuity: a tick, not a numberIs 0.05 ohms the pass mark for bonding?

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There is no single target number. A bonding conductor’s resistance depends on its length and its cross-sectional area, nothing else. So work out what it should read: Table B1 gives milliohms per metre, and you need the length from the installer or the designer.

Example: an expected reading

10 mm² bonding conductor · 30 m
Table B1 · 10 mm² = 1.83 mΩ/m
R = (1.83 × 30) ÷ 1000 = 0.055 Ω
Don’t treat 0.05 Ω as a pass mark for the conductor. It’s a figure that gets quoted, but the conductor’s own reading depends on its length and size. A long run will read more and be perfectly sound; compare against what that length should give.
Compare your two readings. The clamp reading is the conductor end to end; the pipe reading adds the clamp’s contact with the pipe, so it should be only a little higher. A pipe reading well above the clamp reading, or open circuit, means the clamp isn’t making proper contact.

You don’t record a number for bonding. On EIC page 2, under main protective bonding conductors, give the material and size and tick “connection / continuity verified”. The condition report has the same box.

Guidance Note 3 · Appendix B · Table B1

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