Recording RCD test results
Inspection Testing · Lesson 24 · Advanced
Purpose
Record RCD results with device identity, test method, location and restoration evidence.
Learning objectives
- Use the current required method
- Separate field verification from type testing
- Prove polarity through the complete path
- Compare fault current with every affected rating
A bare time in milliseconds cannot be audited unless it is tied to the correct device, rated current, delay class, waveform/test setting, circuit and applicable criterion.
Core theory
Record device BS/EN or product identification as required, type/delay marking, IΔn, test current/method, result, instrument and the circuit(s) protected. Use the schedule field defined by the applicable form.
Where repeated phase-angle tests are legitimately made, record the required/worst result according to current guidance and state diagnostic extras separately. Never copy one board-level result into every circuit without linkage.
Operate the integral test button where required, confirm all poles/open neutral behavior as applicable, restore loads/clocks/controls and record defects, replacements and retests.
| Term | Meaning | Symbol | Unit |
|---|---|---|---|
| Test button | Built-in functional mechanism creating an internal imbalance | Not applicable | Not applicable |
| Worst result | Governing result among required repeated conditions | Not applicable | Not applicable |
| Traceability | Link from result to exact device, circuit, method and instrument | Not applicable | Not applicable |
Assumptions: Supplied readings and criteria are fictional evidence; Current edition and exact equipment data remain governing.
- Compare: Both are below the supplied 300 ms maximum.
- Record: Use the applicable form/method; 201 ms is the slower governing evidence if one value is required.
- Retain: Keep both raw readings in supporting records when useful.
Both pass the supplied limit; 201 ms is the worst observed required result.
Reasonableness check: The decision distinguishes the measured quantity, protective function and equipment rating instead of treating one tester result as a complete certificate.
- Applying obsolete half-rated/5× rules as universal requirements
- Selecting an RCD type from trip time alone
- Checking PFC only against the final-circuit breaker
Where this appears in practice
RCD, polarity and PFC verification confirms correct conductor/device operation and that installed equipment can safely interrupt credible faults.
Knowledge check
Can the same trip time be copied across every circuit protected by one RCD without identifying the shared device?
No. Record the relationship and device-level evidence transparently.
Answer: No. Record the relationship and device-level evidence transparently.
Practical exercise
Audit an RCD schedule for missing type/delay, wrong test multiplier, shared-device ambiguity and unrecorded retest.
Summary
- Current field RCD testing is intentionally simplified
- Polarity requires both topology and final confirmation
- PFC is a worst-case rating and coordination check
Sources and review
- Changes to RCD testing in BS 7671:2018+A2:2022: IET Wiring Matters; 2022; confirm A4:2026/GN3 status; United Kingdom
- BS 7671 and Guidance Note 3: Inspection & Testing: IET; BS 7671:2018+A4:2026 / GN3 10th edition; transition rules apply; United Kingdom
- Minimizing unnecessary live testing for initial verification: IET Wiring Matters; 2025; United Kingdom
- GS38: Electrical test equipment for low-voltage systems: HSE; Fourth edition; Great Britain
Editorial review date: 2026-08-22. Professional electrical review is pending.