I read in !emc-pstc that Rich Nute <[email protected]> wrote (in <[email protected]>) about 'How do I do this test?' on Mon, 8 Dec 2003: > > > >Hi John: > > >> But what it is really NOT to be used for is anything that has wiring >> installed in the walls and/or ceiling voids. This wiring is very >> vulnerable to accidental contact with mains wiring when the building is >> being altered, painted etc. > >In the USA, we violate this principle. As far >as I know, this wiring has not proved vulnerable >to accidental contact with mains wiring.
On the sci.electronics.xxx newsgroups we get quite a few enquiries from householders who have put nails and screws through hidden wiring. > >In the USA, power for doorbells is floating SELV >and is installed in the walls and ceiling voids. >Same for telephone conductors. There are no >requirements for the insulation of these wires >as voltage is SELV and the power is considered >less than that necessary for fire. > >Such wiring cannot be in contact with the mains >wiring in those walls and ceilings. Furthermore, >the mains wiring must be protected against >insulation or conductor damage due to alterations, >etc., by installing various protective devices >and by routing limitations. > > I understand your point, but this is a case where the precautionary principle can reasonably be applied to at least some systems. The household appliance and telecoms people must make their own decisions; I am concerned with professional audio and that industry sector does not use Class II to any extent; there is always provision for earthing. It isn't just my idea, but many people do not know why we use Class I almost exclusively. Safety is, of course, not the only reason; that's why the concept of functional earth exists. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
