Circuit Protection and the 17th Edition of the IEE Regulations

For 17th Edition Consumer Units including the Chint High Integrity Variant please click this link 

With the introduction of the 17th edition major changes came in to force, particularly in the area of Earth Leakage Protection.  The following can only be a summary, full and detailed information should be obtained from the regulations.

Installations should be so designed as to offer proper circuit discrimination so as to ensure maximum safety/convenience in the event of 1 circuit failure, this is particularly important in the case of lighting circuits.

Summary

• Regulation 411.3.3: All socket outlets meant for use by an ordinary peron with a rated current not exceeding 20 amps should be protected by a 30mA RCD.
• Regulation 701.411.3.3: All circuits in a room with a fixed bath or shower should be protected by 1 or more 30mA RCDs.
• Regulation 522.6.6, 522.6.7 and 522.6.8: All cables buried beneath a plaster surface of a wall at less than 50mm should be protected by 30mA RCDs.
• Regulation 411.3.3: All cables installed in metal stud partition walls should be protected by 30mA RCDs.

The following summary table refers to additional protection, generally this is additional to MCBs - Fuses, i.e. earth leakage protection.  Today SP (Single Pole) RCBOs are seen as a convenient method of offering both overload and Earth leakage protection from one device.

Summary Table

For 17th Edition Consumer Units please click this link

There are a number of factors to be taken in to consideration when determining the correct size of cable, what is the length of run, how is the cable being run, vol drop etc. For this reason we do not give specific advice as it should be left to a qualified electrician. However, as a rule of the thumb for general guidance only: 7/8kw - 6mm T&E up to 20m 9/10kw - 10mm T&E up to 20m

Disclaimer- This is general guidance and not meant as a definitive answer as each installation should be considered individually including how the cable is to be run. If in doubt consult a qualified electrician before you make a purchase.