Mel, I believe the requirement for separation between earth and TNV stems from the fact that the PTTs, in particular BT in the UK, are concerned about the mains plugs being incorrectly wired by users. Secondly they fear that the earth from the supply may not be a true earth and a fault occuring in another piece of equipment on the same ring may induce nasties into the earth path. I don't suggest we get into a debate on the whys or wherefores of this, it has been flogged to death in the various committees already.
There are no requirements between SELV circuits and earth. However SELV may be Earthed or unearthed. Please also note that in the new amendment 3 there is a note which states that all references to earth in the standard imply PE. Best regards Barry Singleton Approvals Specialist email:[email protected] Securicor 3net Limited Ringway House Bell Road Daneshill Basingstoke Hants RG24 8FB UK Tel: 44 (0)1256 792174 Fax: 44 (0)1256 840429 ------------- Original Text From: Mel Pedersen <[email protected]>, on 03/01/97 13:18: To: "'TREG'" <[email protected]> Maybe they are confused? There is a requirement (see Fig. 17 in section = 6.3) for a supplementary barrier between your TNV circuit and earth, but = between SELV and earth?? see section 2.3.3 and 2.3.6...I'm not sure = that a barrier between SELV and earth makes sense... Mel Pedersen, Midcom Inc. [email protected] Disclaimers apply.
