Guidance Note 3: Inspection & Testing (Electrical Regulations)

Product Information

A note has been added clarifying that where non-metallic pipes, e.g. plastic, enter the building and are then connected to metallic pipes within the building, the metallic pipes within the building do not normally require protective bonding as they are unlikely to be extraneous-conductive-parts. Reference to insulating sections has been removed. There is a large element of "measure with a micrometer, mark in chalk, cut with an axe" about the decision about what is an acceptable Zs level for a given breaker anyway, in the sense it is a very accurate calculation of something that does not happen - for example if faults actually were zero resistance, they would not actually dissipate any energy and would not get hot - as I'm sure you realise looking at any burnt end will confirm this is not the case ?.

From Table 1, a 60 m 2.5/1.5 mm 2 ring final circuit only shows a change of one in the least significant digit in the reading as you move around the ring, but with the same ring final circuit wired in 4.0/1.5 mm 2, the change is five in the least significant digit on the instrument. This is a change of 25% of the lowest reading. The lowest reading deviates by 20% from the existing rule of thumb, and the highest reading is predicted by the rule of thumb. The longer the circuit, the more noticeable the difference in reading will be on a test instrument. Whilst BS 7671:2018+A2:2022 doesn’t require other types of RCD testing, however additional tests are not precluded and may be useful for fault finding purposes, these tests could include: All mechanical or electrical equipment has a finite lifespan. For RCDs, part of the product standard test procedure is to ensure a minimum number of operating cycles. BS EN 61008 requires RCDs having I Δn > 10 mA are subjected to 2000 operating cycles, each operating cycle consisting of a closing operation followed by an opening operation. This is a combination of manual operation, using the test button and using a test current of I Δn. BS EN IEC 61557-6:2021 Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. Equipment for testing, measuring or monitoring of protective measures. Effectiveness of residual current devices (RCD) in TT, TN and IT system. When the Type A setting is selected on the instrument, a half wave pulsating residual test current superimposed on a smooth direct current of 6 mA is produced, which effectively applies a 1.4 multiplier to the rated residual current (I Δn). For example, if the 30 mA setting is selected, the RCD will be subjected to a test current of 42 mA (30 x 1.4 = 42 mA).Just because the installation does not fully comply with BS 7671:2018+A1:2020, does not necessarily mean it is unsafe, which will depend on the condition of the installation. The inspector must apply engineering judgment to determine if it is safe for continued use. Who can carry out an EICR? An EICR is an electrical installation condition report, on the condition of an electrical installation. The process involves a combination of inspection and testing to determine if the electrical installation is safe for continued use. and on completion, a report is issued. The requirements for RCD testing have been changed and Table 3A (Time/current performance criteria for RCDs) in Appendix 3 has been deleted. Regardless of RCD Type, an alternating current test at rated residual operating current (IMn) is used to verify the effectiveness. Section 702 - Swimming pools and other basins

Predicted measured resistance = r y//r g = 0.5013×0.5013 ÷ (0.5013+0.5013) = 0.2507 Ω Step 3, resistance at Test Point 5 The inspector will require a range of test equipment to enable test results to be obtained. For domestic and the testing of smaller installations, a multi-function installation tester will be sufficient. For larger and more complex installations, other test equipment will be required. Installation test equipment should comply with the relevant BS EN 61557 standard, be in good condition and be formally calibrated. Good quality test leads, probes and crocodile clips complying with the guidance in HSE GS38 that are in good condition are essential for personal safety. Additional requirements have been added for installations where the generating set or sets may operate in parallel with other sources including systems for the distribution of electricity to the public. It is clear to see from the definition that someone carrying out EICRs is required to have adequate education, training, and experience to do so. An inspection and testing qualification place is a good place to start, but it is also necessary that the inspector has the necessary experience. Common mistakes observed on EICRs Section D – Extent and limitations of inspection and testingPredicted measured resistance = r y//r g = 0.6511×0.3515 ÷ (0.6511+0.3515) = 0.2283 Ω Results and conclusion

Some test instruments have a variable trip current setting, if a tripping current of 50 mA at five times I Δn was selected on the Type A setting, a trip current of 350 mA could be simulated (50 x 5 x 1.4 = 350 mA). However, the variable test current feature is not available on all test instruments. For ‘S’ Type time-delayed RCDs, the operating time shall be between 130 ms (minimum) and 500 ms (maximum). S Type time-delayed RCDs are not applicable for additional protection, hence, the operating times are not included in Regulation 643.8. Modifications have been made to Regulation Group 543.7 concerning earthing requirements for the installation of equipment having high protective conductor currents. When carrying out an earth fault loop impedance test at ambient temperature, it is necessary to adjust the value to take into account increased resistance of the conductors due to a rise in temperature caused by load current. Regulation 544.1.1 concerning main protective bonding conductors has also been revised. Chapter 55 - Other equipmentPD IEC/TR 62350:2006 Guidance for the correct use of residual current-operated protective devices (RCDs) for household and similar use. Section 411 contains a number of significant changes. Some of the main changes are mentioned below.

Appendix 4 includes minor changes concerning a cable surrounded by thermal insulation. Appendix 6 Model forms for certification and reporting BS 7671:2018, Tables 41.2, 41.3, and 41.4 indicate the maximum earth fault loop impedance values, it’s important to note that these are the maximum values which should not be exceeded when the cable is at it’s assumed conductor operating temperature (70c). Requirements for IT systems have also been redrafted. Changes also include requirements for fault protection and requirements for protective equipotential bonding. Section 711 Exhibitions, shows and stands A person carrying out an EICR is required to be competent. The term skilled person (electrically) is used in BS 7671:2018+A1:2020, defined as below:However, it is important to remember that Table 3.2 is titled ‘recommended initial frequencies of inspection of electrical installations.’ The first important word is ‘recommended’, it is exactly that, a recommendation and not a legal requirement. It is also important to note that this is for initial frequencies for new installations. It is worth noting that for domestic rented accommodation and houses in multiple occupation, the recommended maximum period between each inspection and test is five years or change of occupancy, which is often overlooked.