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Bonding question
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<blockquote data-quote="Ardet R" data-source="post: 466914" data-attributes="member: 30040"><p>But you seem to say that the distribution cable to the workshop is 50-70mm², this is not the cable size you are meant to be referring to to get the size of the bonding.</p><p></p><p>The bonding should be sized by the incoming cable from the DNO (like that is ever available to test!) for a 100A supply fuse the DNO would usually have a 35 or 25mm² supply cable though if this is an industrial site then the supply cable may be sized for a more substantial supply.</p><p></p><p>If the incoming DNO cable is also 70mm² then the bonding would need to be 25mm², but your distribution cable (SWA using the armour for earthing) would then not meet the size required for bonding and you would need a 25mm² copper conductor back to the origin.</p><p></p><p>If you have your EMT after at the dist board then the switch fuse to dist board earthing/bonding cable also needs to be of sufficient csa. The cable from the switch fuse to the dist board in the workshop is less than the bonding size required then you would have to get to the switch fuse (or go back to the supplying building!)</p><p></p><p>It would be much easier if the supply were TNS!</p></blockquote><p></p>
[QUOTE="Ardet R, post: 466914, member: 30040"] But you seem to say that the distribution cable to the workshop is 50-70mm², this is not the cable size you are meant to be referring to to get the size of the bonding. The bonding should be sized by the incoming cable from the DNO (like that is ever available to test!) for a 100A supply fuse the DNO would usually have a 35 or 25mm² supply cable though if this is an industrial site then the supply cable may be sized for a more substantial supply. If the incoming DNO cable is also 70mm² then the bonding would need to be 25mm², but your distribution cable (SWA using the armour for earthing) would then not meet the size required for bonding and you would need a 25mm² copper conductor back to the origin. If you have your EMT after at the dist board then the switch fuse to dist board earthing/bonding cable also needs to be of sufficient csa. The cable from the switch fuse to the dist board in the workshop is less than the bonding size required then you would have to get to the switch fuse (or go back to the supplying building!) It would be much easier if the supply were TNS! [/QUOTE]
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