Andrew Don't try to explain that double insulation and earthing are both acceptable alternatives - only 1 persion in 10 will understand and the public won't care!
Option 1 - I think knowledgeable technical people in most countries would actually prefer this for the reasons you mention in your 2nd paragraph - but there are very few of these "technical people". Option 2 - Messy & open to continued confusion for everybody - including your own staff. Option 3 - Provided there is double insulation between the hazardous parts and the metal case, remove the double-insulation mark )not allowed on a Class II product) and provide installation instructions as for a normal earthed product (i.e. MUST be earthed). Then if someone does not earth it the product should still be "safe". (This is the way Rich Nute often explains the use of double-insulation in many of HP's earthed products.) My preference is Option 3 -> almost the least effort and probably the least customer and marketing "hostile" reactions (but it will cost a little more for the cable and strain relief). # Additionally it might (or might not?) help with any static control problems - which can get quite nasty in cold areas where the humidity is very low - and with any equipotentialisation problems which could occur because cold-stores are metal walled. Regards John Allen -----Original Message----- From: Andrew Wood [mailto:andrew.w...@landinst.com] Sent: 05 November 2001 14:27 To: 'emc-pstc' Subject: CLASS 11(DOUBLE INSULATED) & 2/3-CORE CABLE All I have a piece of equipment falling under the scope of EN6010. To set the scene it is a low volume product, approx 0.5m cube, stainless steel enclosure and will sit on a bench in food cold storage areas. Mains lead connects via IP68 connector. It incorporates a SMPS for universal mains operation ( current draw approx 0.3A). Because of problems ensuring a reliable earth in some locations for its predecessor, I have specifically designed it to be Class2 (double insulated). Therefore safe for all markets. Now, ironically, I am encountering some "unease" with the UK sales dept. After all everyone KNOWS that a metal box should be earthed. (I don't dismiss this attitude lightly because it is no doubt shared by some of the customer base.) Technically there is no problem with providing a 3-core cable and connecting up the earth conductor. And after all if 2 levels of protection is good, 3 levels is better. Option 1 is obviously to stick with the design as is and educate sales/customers where necessary. Option 2 is to provide a 3core product for the some markets and a 2core product for others. This goes against the original intention to have a universal product. Is there an option 3? ie provide 3core cable and explain in the manual that product is designed to be safe without an earth but the earth may be fitted if desired. What about the square in square symbol? I'm sure that I'm not the first to be looking at these questions. Any and all thoughts would be appreciated. Best regards, Andy. Andrew Wood Engineer (Specials) Land Instruments International England Please excuse following message automatically inserted by server........ 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. ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server. ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
