18th Edition Mythbuster

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Let Cudis shine some light on the 18th Edition. Do I need to install an 18th Edition Consumer Unit? No. There has been no change to the design of a metal consumer unit since the 17th Edition, Amendment 3. However the installation itself and circuit protection included must comply with the current regulations. Do I need to install 100A RCD’s in split load boards? No. The use of diversity factors to determine maximum demand when designing an installation is still an accepted practice in the 18th Edition (following the manufacturers guidelines). In most cases a 63A or 80A RCD would be appropriate, in cases where there is a possibility of overloading the RCD protecting the downstream circuits, then it may be more suitable to install 100A RCD’s. (BS 7671 Chapter 314.1) Do I need to install Type A RCCB’s as standard? No. For general purposes, Type AC RCD’s may be used. Certain installations require the use of Type A, Type B or Type F RCD’s to protect against DC fault current which may become present on the installation. Such installations include Solar PV and Car Charging Equipment. These devices can be installed at the location of the DC installation (at the AC side) and will prevent any DC earth leakage current entering the rest of the installation. (BS 7671 Chapter 531.3.3) Do I need to install a board with RCBO’s to overcome unwanted tripping of RCD’s/RCCB’s? No. The total earth leakage of the circuits protected by an RCD should not be more than 30% of the rated residual operating current (eg. a 30mA RCD, regulation state no more than 9mA of earth leakage detected on the downstream circuits). Bearing in mind that some circuits will naturally have more protective conductor current / earth leakage eg, circuits powering power supply units (like in PC’s) or transformers like LED Drivers. Careful consideration of subdivision of circuits between the 2 protective RCD’s may be enough to combat the accumulation of fault leakage. Although installing all RCBO’s will give more flexibility in the design of installation and reduce the consequences from tripping as only individual circuits will be affected. (BS 7671 Chapter 531.3.2) 6
www.cudis.co.uk Can I use another brands circuit protection in a Cudis consumer unit? Cudis, as the original manufacturer, do not recommend the use of another manufacturers circuit protection product be used in our enclosures, as they have not been designed or tested for use in our enclosures, therefore we cannot guarantee compatibility. As per the 18th Edition, if incompatible products are installed inside a Cudis consumer unit, then the person introducing the product becomes the original manufacturer with the corresponding obligations. (BS 7671 Chapter 536.4.203) Do I need to install AFDD’s? No. Arc Fault Detection Device’s at the moment are only recommended as a means of providing additional protection against fire caused by arc faults in AC final circuits. Although they may be specified in an electrical installation design, if so they should be installed at the origin of the final circuit to be protected and in AC single phase circuits not exceeding 230V. (BS 7671 Chapter 421.1.7 & 532.6) Do the provided clip in plastic blanks, to cover unused ways in a consumer unit, comply with the 18th Edition Regulations? Yes. All of our consumer units conform to BS61439-3 and we ensure that the blanks are firmly secured in place with sufficient stability and durability to maintain the required degrees of protection and appropriate separation from live parts under normal service conditions, taking account of relevant external influences. However, we also offer an MCB Blank which clips into the din rail offering greater levels of stability and durability which may be more suitable in some circumstances. (BS 7671 Chapter 416.2.3) Do I have to install an SPD in a domestic single dwelling? No. Not always. If a risk assessment is carried out and there are NO unacceptable consequences that exist and there is not an increased risk of lightning present. Then an SPD only has to be installed where the total value of the installation and equipment therein, justify having an SPD installed. This will involve a conversation with the customer to determine whether an SPD is required, however it should be considered that the cost of an SPD is usually far less than even one electronic device that may be attached to the installation. (BS 7671 Chapter 443.4) 7
Page 1 and 2: GUIDE TO THE NEW 18 TH EDITION WIRI
Page 3 and 4: www.cudis.co.uk Caravan Parks (708.
Page 5: www.cudis.co.uk Unwanted Tripping (

18th Edition Mythbuster

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