Apologies if this is duplicated, but I don't think it made it through went I sent it yesterday.
Tim, as you are based in the UK, this might be of some interest. According to 523.7 of BS 7671:2008 (commonly referred to as the "Wiring Regs")....... where a cable is totally surrounded by thermal insulation having a greater thermal conductivity than 0.04 Wm-1K-1, the following derating factors are applied: length in insulation(mm) Derating factor 50 0.88 100 0.78 200 0.63 400 0.51 500 or more 0.50 These apply for conductor sizes up to 10mm^2 and are applied to the tabulated value for installation clipped direct to a surface (Reference method C). These are for UK electrical installations and so are not directly relevant to the original posting, but do give some insight into your question. Andy Best Regards, Andrew Wood MInstP Engineer - Special Products LAND Instruments International Stubley Lane, Dronfield, Derbyshire S18 1DJ, England This e-mail and its contents may be confidential, privileged and protected by law. Access is only authorised by the intended recipient. The contents of this e-mail may not be disclosed to, or used by, anyone other than the intended recipient, or stored or copied in any medium. If you are not the intended recipient, please advise the sender immediately. Land Instruments International is registered in London (Reg. No. 1659383) Registered office: Land Instruments International Limited, 2 New Star Road, PO Box 36, Leicester, Leicestershire, LE4 9JQ "Haynes, Tim (SELEX GALILEO, UK)" <[email protected]> Sent by: [email protected] 03/02/2009 09:27 AM To "Kunde, Brian" <[email protected]>, <[email protected]> cc Subject RE: De-Rating Hookup Wire Hi, Do you also need to de-rate the section of wire that is thermally insulated by the cable tie? Maybe the cable tie is too narrow to be of concern – but then what width is needed before de-rating does become necessary? I agree – all de-rating factors need to be applied. Regards Tim ************************ - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]>
