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Do-It-Yourself (DIY) Question & Answer Forum
Earthing conundrum
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<blockquote data-quote="Andy™" data-source="post: 480293" data-attributes="member: 2012"><p>its clear enough. if its TNCS 714.411.203 requires bonding conductor size of 6mm for a neutral upto 10mm, otherwise use table 54.8</p><p></p><p>544.1.1 states that where section 714 applies, then you follow that, which then refers you back to 54.8 in certain conditions, instead of all conditions which would be required by 544.1.1. basically, it allows a smaller bonding conductor or 6mm rather than the usual 10, in certain circumstances</p><p></p><p>but back to the TNS not being allowed etc... unlike other locations (722, 709 etc) which specifically state restrictions on earthing types (usually TNCS), 714 makes no reference to not allowing TNS or TNCS or TT, therefore all are acceptable and can be used</p><p></p><p>as for RCDs being required, in some cases under 714 it will be required, 714.411.3.3. normal columns it doesnt apply to</p><p></p><p>back to ADS and your disconnection times. if you have a TN system, then its unlikely your Zs will be too high to use the MCB / fuse. you probably will require one for TT though</p><p></p><p>so, feel free to fit an RCD if you want even if its not required, but there is no need to ditch your TNS earth and TT it</p></blockquote><p></p>
[QUOTE="Andy™, post: 480293, member: 2012"] its clear enough. if its TNCS 714.411.203 requires bonding conductor size of 6mm for a neutral upto 10mm, otherwise use table 54.8 544.1.1 states that where section 714 applies, then you follow that, which then refers you back to 54.8 in certain conditions, instead of all conditions which would be required by 544.1.1. basically, it allows a smaller bonding conductor or 6mm rather than the usual 10, in certain circumstances but back to the TNS not being allowed etc... unlike other locations (722, 709 etc) which specifically state restrictions on earthing types (usually TNCS), 714 makes no reference to not allowing TNS or TNCS or TT, therefore all are acceptable and can be used as for RCDs being required, in some cases under 714 it will be required, 714.411.3.3. normal columns it doesnt apply to back to ADS and your disconnection times. if you have a TN system, then its unlikely your Zs will be too high to use the MCB / fuse. you probably will require one for TT though so, feel free to fit an RCD if you want even if its not required, but there is no need to ditch your TNS earth and TT it [/QUOTE]
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