pg 6-10 Domestic Electrical Installer – Module 6: Electrical Inspection, Testing & Documentation

A set of flashcards covering essential concepts from Domestic Electrical Installer Module 6, including pre-work surveys, continuity testing, bonding resistance limits, ring final circuit verification, and safety practices.

What is the purpose of a pre-work survey in electrical testing?

To identify earthing arrangements, disconnection times, isolation requirements, required labels, hazards, special locations, and equipment needs before work begins.

Which document sets the maximum required disconnection times that must be verified during a pre-work survey?

BS 7671.

During a pre-work survey, what standard must test equipment and leads comply with to be deemed safe and suitable?

GS38.

Which three elements make up Automatic Disconnection of Supply (ADS) protection?

Protective earthing, protective equipotential bonding, and automatic disconnection in case of a fault.

Which test verifies that circuit protective conductors (CPCs) are continuous and able to operate protective devices within required times?

Continuity of circuit protective conductors test.

What instrument is used to perform continuity tests on protective conductors?

A low-resistance ohmmeter.

In continuity testing, what do the symbols R1, R2 and Rn represent?

R1 = line conductor resistance, R2 = circuit protective conductor resistance, Rn = neutral conductor resistance.

Which test method links the phase and CPC at the distribution board and measures resistance at the accessory to obtain R1 + R2?

Test Method 1 (R1 + R2 test).

Which continuity method employs a long ‘wander’ lead from the main earth terminal to distant points?

Test Method 2 (wander or long-lead method).

What is the maximum acceptable resistance for main or supplementary bonding conductors when tested?

0.05 Ω or less.

Why must metallic enclosures such as conduit or trunking be inspected along their length during continuity testing?

To ensure they provide a sound protective conductor path with no breaks or excessive resistance.

According to BS 7671 643.2.1, which conductors must be verified for continuity in a ring final circuit?

Line, neutral, and circuit protective conductors (all live conductors of the ring).

What three resistance readings are recorded in Step 1 of ring final circuit continuity testing?

End-to-end resistance of the line (R1), neutral (Rn), and CPC (R2) conductors.

For a 2.5 mm² live conductor ring with a 1.5 mm² CPC, how should the CPC’s resistance compare to the line and neutral resistances?

The CPC resistance should be about 1.67 times higher.

What safety procedure must always precede any continuity or resistance testing on a circuit?

Safe isolation of the installation.

What could happen if an exposed-conductive-part is left without an effective earth connection?

It could become live during an earth fault, leaving no fault protection and posing a shock risk.

How can the result of an R1 + R2 test be further used besides confirming continuity?

To determine the earth fault loop impedance (Zs) at the test point.

Why must allowance be made for test-lead resistance when using a low-resistance ohmmeter?

Because the lead resistance can otherwise inflate measured values and give inaccurate continuity results.