Dead tests first, live tests second. That sequence is not optional — it is a BS 7671 requirement. Dead tests confirm the circuit is safe to energise. Live tests confirm the protective devices will operate correctly under fault conditions. This guide explains every test, the correct order, and common mistakes.
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Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.
Dead tests are carried out with the supply isolated and prove the circuit is safe to energise: continuity of conductors (R1+R2 and ring), insulation resistance, separation, polarity and earth electrode resistance. Live tests are carried out with the supply energised and prove the protection works: earth fault loop impedance (Zs), prospective fault current, RCD operation, phase sequence and functional testing.
BS 7671 Regulation 643.1 requires the dead tests of Regulations 643.2 to 643.6 to be carried out in that order before the installation is energised. The live tests then follow under Regulations 643.7 to 643.10.
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Electrical testing is not a pick-and-choose exercise. The test sequence in BS 7671 Chapter 64 prescribes a specific order: visual inspection first, then the dead tests, then the live tests. This sequence exists for one reason — safety. Regulation 643.1 is explicit that the tests of Regulations 643.2 to 643.6 are carried out in that order before the installation is energised.
Dead tests verify that the circuit is fundamentally sound before you energise it. Continuity testing confirms that the protective conductor (the earth wire) is connected throughout the circuit and will carry fault current to the protective device. Insulation resistance testing confirms there are no short circuits or insulation breakdowns between conductors. Polarity testing confirms that line and neutral are not transposed.
If you skip dead tests and go straight to live testing, you are energising a circuit without knowing whether the earth is connected, the insulation is intact, or the polarity is correct. A circuit with a broken earth will not trip the protective device during a fault. A circuit with damaged insulation may cause a short circuit when energised. A circuit with reversed polarity may leave exposed metalwork live. Each of these scenarios can cause injury or death.
The testing sequence is not guidance — it is a requirement. Follow it every time.
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Every test in BS 7671 Chapter 64 is either a dead test (supply isolated) or a live test (supply energised). The table below maps each test to its regulation reference, the supply state required, and the instrument used.
Before performing any dead test, the circuit or installation must be safely isolated. This means the supply is disconnected, locked off, and proven dead using an approved voltage indicator. The full safe isolation procedure follows GS38 (HSE Guidance Note 38) and involves:
Only when the circuit is confirmed dead should you proceed with dead testing. This procedure applies whether you are doing initial verification or periodic inspection. On a periodic inspection of an existing installation, you isolate each circuit in turn, perform the dead tests, then re-energise for live tests.
Never assume a circuit is dead. Always prove dead with an approved voltage indicator before touching any conductor. "I turned it off at the board" is not proof of isolation — the circuit could be back-fed, the MCB could be mislabelled, or the wrong circuit could be isolated.
Dead tests are performed with the circuit de-energised (isolated). They are specified in BS 7671 Regulations 643.2 to 643.6 and, where an earth electrode is fitted, 643.7.2 — and must be carried out in that order before the circuit is energised. The dead tests are:
Uses a low-resistance ohmmeter to measure the resistance of the circuit protective conductor (CPC) from the distribution board to the furthest point. This confirms the earth wire is connected and will carry fault current. The measured R1+R2 value is also used to calculate the expected Zs (R1+R2 + Ze = Zs). See the continuity testing guide for the full procedure.
Specific to ring circuits. The three conductors (line, neutral, CPC) are tested individually to confirm they form a continuous ring with no breaks or interconnections. This involves measuring end-to-end resistance of each conductor, then cross-connecting and measuring at each socket to verify the ring is complete.
Measures the resistance between live conductors, and between live conductors and the protective conductor, at the DC test voltage set by BS 7671 Table 64. Values below the minimum indicate insulation breakdown — a fault path that can cause leakage current, nuisance RCD tripping, or a short circuit.
Source: BS 7671 Table 64. Where connected equipment may be damaged or affect the result, test before connection; a follow-up test at 250 V DC then applies, with a minimum of 1.0 MΩ (Regulation 643.3.3).
See the insulation resistance testing guide for detailed procedures.
Confirms that single-pole switching devices are connected in the line conductor only (not the neutral), that socket outlets are correctly wired (line on the right when viewed from the front), and that the centre contact of Edison screw lampholders is connected to line. Polarity can be verified using the continuity tester as part of the R1+R2 test.
For TT systems, the earth electrode resistance must be measured using the fall of potential method. This confirms the electrode provides a low enough resistance path for the RCD to operate within disconnection times.
Live tests are performed with the supply energised. They sit later in the same Chapter 64 test sequence — earth fault loop impedance (643.7.3), prospective fault current (643.7.3.201), additional protection including RCD operation (643.8), phase sequence (643.9) and functional testing (643.10) — and must only be carried out after the dead tests have been completed satisfactorily.
Measures the total impedance of the earth fault loop for each circuit — from the point of the fault, through the CPC, back through the MET, and through the supply transformer. The measured Zs must be less than the maximum value in BS 7671 Table 41.2, 41.3, or 41.4 for the protective device rating and type. If Zs is too high, the protective device will not disconnect within the required time — in a TN system, 0.4 s for final circuits up to 63 A and 5 s for distribution circuits (per Table 41.1). See the earth fault loop impedance guide for full details.
Measures the maximum current that would flow during a short circuit (PSCC) or an earth fault (PEFC) at the origin of the installation. The protective devices must have a breaking capacity equal to or greater than the prospective fault current. A typical domestic supply has a PSCC of 2 to 6 kA at the origin. The measurement is taken at the main distribution board. Use the prospective fault current calculator to verify.
BS 7671 Regulation 643.8 requires the effectiveness of additional protection by RCDs to be verified with suitable test equipment to BS EN 61557-6. A general, non-delay type RCD is deemed effective where it disconnects within 300 ms at its rated residual operating current (IΔn). In practice you test at x1 and x5 of IΔn; the ramp test (gradually increasing current until trip) confirms the actual trip current. The test uses the RCD function on a multifunction tester, connected at a socket or accessory on the protected circuit. See the RCD testing guide for detailed procedures.
Manual operation of each switchgear device, interlock, and control to confirm correct function. This includes operating every MCB, RCBO, and RCD manually, testing isolator switches, checking that interlocked devices operate in the correct sequence, and verifying emergency switching (such as fireman's switches or emergency stop buttons).
Whether you are doing dead tests or live tests, speak your readings into Elec-Mate: 'Ring 1, R1+R2 0.32, IR 200 meg, Zs 0.89…
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Try the certificate tools freeHere is the complete test sequence as specified by BS 7671 Chapter 64 and IET Guidance Note 3. Follow this order for every initial verification. For periodic inspections, the same sequence applies per circuit (isolate, dead test, re-energise, live test).
If any dead test fails, do not energise the circuit. Investigate the fault, rectify it, and re-test before proceeding. A failed insulation resistance test could indicate a short circuit that will trip the protective device (or worse) when energised. A failed continuity test means the earth is not connected and the circuit has no fault protection.
Even experienced electricians can fall into bad habits with the test sequence. These are the most common mistakes:
All test results — both dead and live — are recorded on the schedule of test results that accompanies the EICR or EIC. Each circuit has a row on the schedule with columns for every required test value.
The AI in Elec-Mate automatically compares your measured values against BS 7671 maximum permitted values and flags any that exceed the limit. If a value fails, it suggests the correct observation code (C1, C2, C3, or FI) and the matching regulation number.
The app guides you through dead tests then live tests in the correct order. Voice-enter your readings…
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