Regulations, Standards and Safety
This domain tests how well you can apply the National Rules for Electrical Installations (ET101, derived from the HD 60364 / IEC 60364 family) alongside Irish health and safety law, and how you demonstrate compliance through isolation practice and certification.
Structure of the rules
Parts 1 to 7 cover scope and definitions, protection, selection and erection of equipment, verification, and special locations such as bathrooms, swimming pools, construction sites and agricultural premises. Part 4 protection includes basic protection (insulation, barriers, IP ratings), fault protection by automatic disconnection of supply, overcurrent and overvoltage protection. Part 6 verification is what produces your test results and certificates.
Disconnection and RCDs
Automatic disconnection times are 0.4 s for final circuits up to 32 A and 5 s for distribution circuits and fixed equipment above 32 A. A 30 mA RCD provides additional protection, not a substitute for earthing and bonding. Select the RCD type for the load: type AC for plain sinusoidal AC, type A where pulsating DC is present, type B where smooth DC can appear, such as three-phase drives, EV charging and some PV inverters.
Worked example
A 9.5 kW shower at 230 V draws 9500 / 230 = 41.3 A. A 40 A device fails In ≥ Ib, so a 45 A MCB is chosen, with a cable whose corrected Iz is at least 45 A. The measured Zs must not exceed the maximum for that device at 0.4 s, and the bathroom location requires 30 mA RCD protection and supplementary bonding where the rules call for it.
Traps
Applying 0.4 s to a distribution circuit; treating an RCD as a replacement for a CPC; quoting UK guidance numbers where ET101 applies; and comparing Zs with the cold-conductor maximum instead of the value at operating temperature.