R1+R2 Continuity Testing
Testing & Inspection · C&G 2365 Unit 304 / 2391 · Premium section
Continuity of protective conductors is the first dead test, and the usual method links the line conductor to the at the board, then measures between line and cpc at each point on the circuit. The reading at each point is for that point — the loop the fault current would take through the circuit's own conductors.
The instrument is a low-resistance ohmmeter, and the leads must be nulled first: a couple of tenths of an ohm of test lead looks exactly like a slightly loose termination once you are reading fractions of an ohm. The wander-lead method is the alternative where linking at the board is impractical, at the cost of a long lead whose own resistance you must account for.
The number matters twice. It confirms the protective conductor is continuous, and it feeds the calculation: Zs equals plus . A reading that drifts, or that is far lower than the cable length suggests, usually means a parallel path through metalwork rather than a good connection.
Common questions
- Is there a free R1+R2 Continuity Testing quiz?
- sits in the Testing & Inspection section, which is part of TradeTraining Premium — but the app is free to start, sample questions are open to everyone, and the free sections cover the fundamentals first.
- Where does R1+R2 Continuity Testing sit in the City & Guilds scheme?
- maps to C&G 2365 Unit 304 / 2391. On TradeTraining it lives in the Testing & Inspection section as bite-size lessons with practice questions.
- What does R1+R2 actually stand for?
- R1 is the resistance of the circuit's line conductor and R2 the resistance of its protective conductor. Measured together, they give the resistance of the path a line-to-earth fault would take within the circuit itself.
- Why do you null the test leads first?
- Because you are measuring in fractions of an ohm and the leads themselves have resistance. Without nulling, every reading is inflated by the leads and a healthy circuit can look like a poor one.