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Educational use: ElectraCore supports learning and preliminary checks. It does not replace a competent electrician or engineer. Verify results, equipment data, and current local regulations before installation or live work.
Courses/Inspection & Testing/Insulation Resistance

lesson · 7min · Lesson 14 of 36

Electronic equipment and IR testing

Course syllabusCourse overview
01Test Sequence & Preparation
  1. ReadWhy test sequence matters: safety
  2. ReadDead tests before live tests
  3. ReadTest instrument calibration and leads
  4. ReadBS 7671 Appendix 6 test schedule
  5. quizPreparation quiz
02Continuity Testing
  1. ReadRing final continuity: three tests explained
  2. ReadProtective conductor continuity
  3. ReadMain and supplementary bonding continuity
  4. ReadContinuity test results: limits and recording
  5. exerciseContinuity exercise
03Insulation Resistance
  1. ReadIR testing principles: 500V, 1000V
  2. ReadTesting between live conductors and earth
  3. ReadLow IR readings: causes and diagnosis
  4. ReadElectronic equipment and IR testing
  5. quizIR testing quiz
04Earth Fault Loop Impedance
  1. ReadExternal impedance Ze measurement
  2. ReadTotal loop impedance Zs measurement
  3. ReadComparing Zs to Table 41.1 limits
  4. ReadCorrecting excessive Zs readings
  5. exerciseZs measurement exercise
05RCD Testing
  1. ReadRCD tripping current tests: half-rated and rated
  2. ReadRCD trip time testing at 1× and 5× rated current
  3. ReadMaximum trip time limits for different RCD types
  4. ReadRecording RCD test results
  5. quizRCD testing quiz
06Polarity & PFC
  1. ReadPolarity testing: dead and live methods
  2. ReadPFC measurement at origin and boards
  3. ReadVerifying PFC against device ratings
  4. quizPolarity and PFC quiz
07Certification & EICRs
  1. ReadEIC: Electrical Installation Certificate
  2. ReadMinor Works Certificate: when to use
  3. ReadEICR: periodic inspection
  4. ReadObservation codes C1, C2, C3, FI
  5. exerciseEICR coding exercise
08Final Assessment
  1. exerciseFull mock test schedule: complete it
  2. quizFinal written assessment
Lesson · 7min
SIMPLIFIED CHARGE MODEL · I = Q / t+electron drift = current1 A = 1 coulomb per second
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In this lesson

PurposeCore theoryWorked exampleKnowledge checkSources

In this lesson

PurposeCore theoryWorked exampleKnowledge checkSources
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ElectraCore lesson handout

Electronic equipment and IR testing

Inspection Testing · Lesson 14 · Advanced

AdvancedReview: professional review pending

Purpose

Protect electronic equipment during IR testing while still obtaining meaningful wiring evidence.

Before you beginSafe isolation and test preparation · Continuity and protective-device fundamentals

Learning objectives

  • Select a safe valid method
  • Protect connected equipment
  • Interpret measured versus design values
  • Diagnose without bypassing protective evidence

LED drivers, dimmers, controls, appliances, SPDs, filters, VSDs and monitoring equipment may be damaged or bias results. ‘Disconnect everything’ can also leave untested cable sections, so plan each boundary.

INSULATION TEST BOUNDARY AND LEAKAGEINSULATION TEST BOUNDARY AND LEAKAGEORIGINCIRCUITtest pointinspect · isolate · prove · measure · interpret · restore · record

Core theory

Use manufacturer and current standard guidance to disconnect, isolate or link conductors around sensitive equipment. Record what was excluded and how its supply cable was tested.

Where equipment cannot reasonably be disconnected, an approved lower test voltage or combined-live-to-earth method may be used only under applicable rules; record the method and limitations.

After discharge and reconnection, verify polarity, settings, protective paths and function. Do not assume an appliance's internal electronic leakage represents fixed-wiring failure.

Terms, symbols, and units
TermMeaningSymbolUnit
SPDSurge protective deviceNot applicableNot applicable
EMC filterNetwork that can create intentional leakage pathsNot applicableNot applicable
Test boundaryExact conductors/equipment included in a resultNot applicableNot applicable
Worked exampleAn SPD is rated for normal mains service but its manufacturer requires disconnection for 500 V DC IR testing.

Assumptions: Supplied values and device limits are fictional design evidence; Instrument uncertainty and current edition data remain to be checked.

  1. Follow data: Safely disconnect/isolate the SPD as instructed.
  2. Test: Test fixed wiring with the SPD excluded and record the boundary.
  3. Restore: Discharge, reconnect correctly and verify indication/protection before service.

Do not test through the SPD contrary to its instructions; preserve wiring evidence and record exclusion/restoration.

Reasonableness check: The conclusion retains units, test boundary and protective-device context; one favorable reading cannot excuse an unsafe method.

Common mistakes
  • Testing connected electronics at an unsuitable DC voltage
  • Treating parallel paths as the designed CPC
  • Comparing a measured Zs with the wrong device curve or an unqualified tabulated value

Where this appears in practice

IR and loop verification provide complementary evidence: insulation limits unintended current paths while loop impedance supports automatic disconnection under faults.

SafetyIR testing charges capacitance and can damage equipment; isolate, disconnect/protect devices, control access and discharge after test. Loop testing is live and Ze procedures may disturb earthing and bonding. Use declared data or a controlled competent method, check diverted current and restore every connection.
Local code checkUse the BS 7671 edition applicable to the work, current Guidance Note 3, exact protective-device data, supply operator information and instrument/manufacturer instructions. During the 2026 transition, record the actual edition used. Ze work can remove a protective/bonding path and expose diverted-neutral current hazards; direct measurement is not automatically preferable to reliable declared supply data.

Knowledge check

May an IR result omit connected equipment without recording the boundary?

No. The certificate must show the meaningful extent/method and any limitation.

Answer: No. The certificate must show the meaningful extent/method and any limitation.

Practical exercise

Plan IR testing for a circuit with SPDs, smart controls, LED drivers and an inaccessible fixed appliance.

Summary

  • Choose voltage and connections from actual equipment
  • Loop boundaries must be explicit
  • Compare results with exact current design evidence

Sources and review

  • BS 7671 and Guidance Note 3: Inspection & Testing: IET; BS 7671:2018+A4:2026 / GN3 10th edition; transition rules apply; United Kingdom
  • Guidance Note 3 errata and diverted-neutral safety note: IET; GN3 9th-edition errata; use current GN3 procedure; 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.

Educational material for learning and preliminary checks. Verify current local requirements and exact equipment instructions. This lesson does not replace competent professional work.

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