What is
EICR Testing

What EICR testing actually involves and why each test matters

EICR testing is more than just a visual look at the consumer unit. It involves systematic electrical measurements that verify safety in ways human eyes cannot detect. Understanding what's tested helps you appreciate the value of EICRs and why proper testing takes 2-4 hours.

Part 1: Visual inspection.

• Examine consumer unit (fuse board) for: type, age, RCD protection, condition, accessibility, labelling.
• Check sockets and switches for: damage, scorching, looseness, age.
• Inspect light fittings and switches for: damage, missing parts, modifications.
• Examine visible cabling for: damage, wear, correct routing, support clips.
• Check earthing arrangements: main bonding to gas/water, supplementary bonding in bathrooms.
• Inspect for any non-compliant additions or modifications.
• Look at protective devices (fuses, MCBs, RCDs) for correct type and rating.
• Typically takes 30-60 minutes for a 3-bedroom property.

Part 2: Test 1 - Insulation resistance test.

• What it measures. Insulation resistance between live conductors and earth, plus between live conductors themselves.
• Why it matters. Damaged or degraded insulation can cause electric shock, fire or unreliable circuit operation.
• How it works. Specialised insulation tester applies 250V or 500V DC to circuit. Measures current leakage through insulation.
• BS 7671 requirement. Insulation resistance must be greater than 1 megohm.
• Typical good reading. Hundreds of megohms or 'OL' (over limit) on tester.
• Failures. Damaged cable insulation, water ingress, deteriorated old wiring.
• Per circuit. Each circuit tested separately with all loads disconnected.

Part 2: Test 2 - Continuity test.

• What it measures. Earth conductor continuity throughout circuit. Ring main continuity for socket circuits.
• Why it matters. Broken earth means no protection from earth faults. Unsafe.
• How it works. Tester sends low current through earth path. Measures resistance.
• BS 7671 requirement. Earth continuity should be very low resistance (typically less than 1 ohm).
• Ring main continuity. Specifically for socket ring circuits. Confirms ring is intact.
• Per circuit. Each circuit's earth path tested.
• Common issues. Damaged earth wire, poor terminations, broken ring at junction.

Part 2: Test 3 - Polarity test.

• What it measures. Confirms live and neutral conductors are correctly identified at each accessory.
• Why it matters. Reversed polarity means switches break neutral instead of live. Switching off doesn't isolate fault. Lamps stay live.
• How it works. Tester confirms live conductor reaches the live terminal at sockets and switches.
• BS 7671 requirement. All accessories must have correct polarity.
• Common issues. Reversed wiring at sockets, particularly older installations or DIY work.
• Per accessory. Each socket and switch checked.

Part 2: Test 4 - RCD trip time test.

• What it measures. Time RCD takes to trip when fault current flows.
• Why it matters. RCDs save lives by tripping quickly during earth faults. Slow or non-tripping RCD is dangerous.
• How it works. RCD tester injects controlled fault current at multiple test currents (e.g. 1x, 5x rated trip).
• BS 7671 requirement. 30mA RCD must trip within 40ms at 5x rated current. Within 300ms at rated current.
• Common issues. RCD failed (mechanical failure), wrong type for application, missing on circuits requiring it (showers, outdoor).
• Per RCD. Each RCD tested individually.

Part 2: Test 5 - Earth fault loop impedance.

• What it measures. Total resistance of earth fault path from circuit to substation and back.
• Why it matters. Determines fault current and whether protective devices will operate within safe time.
• How it works. Loop impedance tester measures path including supply transformer, neutral, earth.
• BS 7671 requirement. Specific maximum values per circuit type and protective device.
• Common issues. Long cable runs, undersized cables, poor earthing arrangements.
• Per circuit. Calculated for each circuit type.

Test equipment used:

• Multifunction tester (MFT). Combines insulation, continuity, loop impedance, RCD testing in one unit. Common UK brands: Megger, Fluke, Kewtech, Metrel.
• Approved voltage indicator. Confirms circuits are dead before testing. Two-pole tester typical.
• Proving unit. Verifies voltage indicator works correctly.
• Calibrated to UK standards. All test equipment annually calibrated and certified.
• Cost of equipment. Professional MFT £300-£1500. Annual calibration £50-£150.

What's documented during testing:

• Each test result recorded on EICR document.
• Tabular format with circuit name, test type, measured value, pass/fail.
• Defects noted with C1, C2, C3 or FI codes.
• Visual observations recorded.
• Limitations of testing (anything not fully tested).
• Overall result: Satisfactory or Unsatisfactory.
• Recommendations for any required action.

Power requirements during testing:

• Power must be off for insulation resistance test (could damage equipment).
• Power on for RCD and loop impedance tests.
• Each circuit tested individually, briefly powered off then on.
• Total power-off time 30-60 minutes spread across visit.
• Some whole-property power-off briefly (15-30 minutes).
• Disconnect sensitive equipment beforehand if concerned.

Why some tests reveal issues that visual inspection misses:

• Insulation degradation invisible until tested.
• Internal cable damage hidden by outer sheath.
• Reversed polarity not visible without testing.
• RCD mechanical failure can occur without external signs.
• Earth path interruptions can be intermittent.
• Loop impedance issues only revealed through measurement.
• This is why EICR testing is more thorough than just visual checks.

Common UK EICR test failures:

• Old installations. Insulation resistance failure in pre-1970s rubber-insulated cables.
• Bathroom modifications. Missing or insufficient bonding.
• Outdoor lights. Damaged cables and lack of RCD protection.
• Kitchen rewires. Polarity errors at sockets.
• Older fuse boards. No RCD protection (typically C3 not C2).
• DIY additions. Various issues from unqualified work.
• Garage and outbuilding installations. Insulation degradation from moisture.

What you can do to prepare for EICR testing:

• Provide access to consumer unit (clear any storage).
• Provide access to all sockets and switches.
• Inform of any specific concerns or recent issues.
• Provide previous EICR if available.
• Plan for power-off periods (save work, defrost food, etc).
• Be present or available for questions.
• Allow 2-4 hours for typical 3-bedroom property.

Knowing what EICR testing involves helps UK property owners understand the value of a thorough inspection. Our full EICR Help hub covers EICR cost, validity periods, legal requirements and broader electrical inspection guidance for UK homes and businesses.