Where the designer decides to depart from the requirements of BS 7671, the resulting degree of safety must not be less than that obtained by compliance with the Regulations. The designer is responsible for the safety of the design. Any intended departure from the requirements of BS 7671, although the designer is confident regarding safety, must be recorded on the Electrical Installation Certificate. There is a difference between an intended departure and a non-compliance; points to note: - They have also estimated that around half of accidental fires caused in UK homes are due to electricity, the majority due to cooking appliances and white goods. The area is divided by 3.142 (Π) and the square root (√) of the answer is the radius (r). Multiply the radius by 2 and you have the diameter. Why are Different Cables and Flexes Used for Different Things?

Always look to cross-reference information provided with the 18th edition full guide when necessary. A larger size cable may also be used in situations where an electric supply needs to be run over a long distance. Using the incorrect size cable in this case may cause a large amperage drop resulting in not enough electrical power actually making it to the end of the cable to actually power the item. What About the Size of the Earth Wire? The first table below is for cables which are installed by Method 103 “Surrounded by thermal insulation including in a stud wall with thermal insulation with cable not touching the wall”.

For a TT arrangement, 21 0 is the usual stated maximum resistance of the distributor's earth electrode at the supply transformer. The resistance of the consumer's installation earth electrode should be as low as practicable and an The installer could for example, select as they deem appropriate; trunking, conduit, cable gland or cable entry accessories to minimise the opening around the cables. (d) the consumer's tails also need to be protected to avoid any foreseeable damage and, where entering a ferrous enclosure, do so through the same entry point. Information on Special Installations & Locations (Part 7 in the 18th edition bs7671) is only mentioned sparingly in this guide. However, some notes are included on the specific sections relating to Bathroom & Shower fittings, as well as advice on underfloor heating installations. Where consumers tails are protected against fault current by the distributors cut-out, the method of installation, maximum length and minimum cross-sectional area (csa) of the tails must comply with the requirements of the distributor. The three-way division of an installation can provide ways unprotected by RCDs for, say, fire systems and for two separate 30 rnA RCCBs to ensure that part of the installation will remain on supply in the event of a fault. Unprotected circuits will usually need to be installed in earthed metal conduit or wired with earthed metal-sheathed cables, see Figure 3.6.3(iii). 534

Band I (extra-low voltage) circuits must not be contained within the same wiring system (for example, trunking) as Band II (low voltage) circuits unless: An extractor fan supplied from a lighting circuit for a bathroom without a window should have its own means of isolation, as otherwise replacement or maintenance of the fan would have to be carried out in the dark. An isolation switch for a fan with an overrun facility will need to be triple-pole (switch wire, line and neutral), and must be installed outside zones 0, 1 and 2. Supplementary bonding

Updates to the 17th Edition Wiring Regulations (BS 7671)

BS 7671:2018 does not specify requirements for protection against transient overvoltages due to direct or nearby lightning strokes on the structure. For risk management for protection against transient overvoltages due to direct or nearby lightning strokes on the structure, see BS EN 62305-2. The situations in which you would use a larger cable size really depends. As mentioned, appliances such as electric power showers, large cookers, electric car chargers etc. will all draw larger amounts of current so will generally require a larger size cable to supply the required current and prevent too much current being drawn which can cause overheating and the potential for the cable to catch fire!

It is OK, when working on a building with the old colours, to joint the new to the old as long as the joint itself is done correctly. Yes, 230 V fittings may be installed above a shower or bath, but they must be at least IPX4. Extractor fans The cited distances are quoted within BS 6891:2015 Specification for the installation and maintenance of low pressure gas installation pipework of up to 35 mm (R 1114) on premises, clause 8.4.2. an intended departure must be recorded on the Electrical Installation Certificate an intended departure not recorded on the Electrical Installation Certificate is unacceptable, as it is simply a non-compliance and the certificate would, therefore, be worthless. The 101 value (in amperes) is normally marked on the device in a rectangle, for example, ~OOOIA and for the majority of applications the prospective fault current at the terminals of the circuit-breaker should not exceed this value. For domestic installations the prospective fault current is unlikely to exceed 6 kA, up to which value the len will equal lcs.Meter tails fall into two categories, supplier's tails and consumer's tails and there is a need to differentiate between the two. Regulation 701.415.2 (last paragraph) allows supplementary bonding to be omitted where the location containing a bath or shower is in a building with a protective equipotential bonding system in accordance with Regulation 411.3.1.2 and provided all of the following conditions are met: b) at a nominal voltage of 230 V AC single-phase or 400/230 V AC three-phase (c) supplied through a distributor's cut-out having a fuse or fuses rated at 100 A or The cables between the electricity meter and the consumer unit, known as the consumer's tails, are part of the consumer's installation and should be insulated and nonmetallic sheathed or insulated and enclosed within containment, for example, conduit or trunking. Consumer's tails are provided by the installer and are the responsibility of the owner of the electrical installation. 514.3.1 This can be further complicated by the location in which they will be installed and how effectively a given cable will be able to disperse heat e.g. a cable installed in an empty stud wall will dissipate heat much easier than a cable in a loft that buried under 200mm of insulation, so this needs to be considered also.

If you snip one of the wires and look at it face down you will see it’s cross section. Obviously this is a circle. The area, or cross sectional area of this circle is 1.5 mm square or 2.5 mm square.

What About the Size of the Earth Wire?

Preparation of instructions for use. Structuring, content and presentation General principles and detailed requirements and BS 4940 series (1994) Technical information on construction products and services. The size and complexity of the installation will dictate the nature and extent of the manual. For all other cases than above a risk assessment to determine the Calculated Risk Level CRL shall be conducted to 443.5 (see Appendix lET Guidance Note 1 for further information). Note: