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Do-It-Yourself (DIY) Question & Answer Forum
Meter Tail installation that exceed 3 meters length passing through the building fabric?
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<blockquote data-quote="unphased" data-source="post: 273204" data-attributes="member: 6"><p>There is a regulation in BS7671 that may be the root of the 3m nonsense spouted about tails.</p><p></p><p>433.2.2 The device protecting a conductor against overload may be installed along the run of that conductor if the part of the run between the point where a change occurs (in cross-sectional area, method of installation, type of cable or conductor, or in environmental conditions) and the position of the protective device has neither branch circuits nor outlets for connection of current-using equipment and fulfils at least one of the following conditions:</p><p></p><p>i It is protected against fault current in accordance with the requirements stated in in Section 434.</p><p></p><p>ii Its length does not exceed 3m, it is installed in such a manner as to reduce the risk of fault to a minimum.....</p><p></p><p>I believe this could be the origin of the misinformed requirement. If you had tails at 25mm2 from the origin, and wanted to serve a fuseboard more than 3m away, provided you kept the tails at 25mm2 all the way and met the other requirements then there is no need to install another protective device (switched fuse) along the run. However, if you wanted to save some dosh and, say, have the first 3m in 25mm2 and install the remaining in 16mm2 if it was an exceptionally long run, then it could be done using that reg. This is an example of how hearsay and misinformation gets entrenched in this industry.</p></blockquote><p></p>
[QUOTE="unphased, post: 273204, member: 6"] There is a regulation in BS7671 that may be the root of the 3m nonsense spouted about tails. 433.2.2 The device protecting a conductor against overload may be installed along the run of that conductor if the part of the run between the point where a change occurs (in cross-sectional area, method of installation, type of cable or conductor, or in environmental conditions) and the position of the protective device has neither branch circuits nor outlets for connection of current-using equipment and fulfils at least one of the following conditions: i It is protected against fault current in accordance with the requirements stated in in Section 434. ii Its length does not exceed 3m, it is installed in such a manner as to reduce the risk of fault to a minimum..... I believe this could be the origin of the misinformed requirement. If you had tails at 25mm2 from the origin, and wanted to serve a fuseboard more than 3m away, provided you kept the tails at 25mm2 all the way and met the other requirements then there is no need to install another protective device (switched fuse) along the run. However, if you wanted to save some dosh and, say, have the first 3m in 25mm2 and install the remaining in 16mm2 if it was an exceptionally long run, then it could be done using that reg. This is an example of how hearsay and misinformation gets entrenched in this industry. [/QUOTE]
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Meter Tail installation that exceed 3 meters length passing through the building fabric?
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