Joe, It may be possible for permanently connected equipment to have a second connection to earth, but for equipment connected to the mains supply via a plug, it does not seem feasible to have a second connection to earth. I do not believe that this a solution that the standards or electrical codes would accept.
A Class 1 product depends on basic insulation and earthing for its electrical safety. The design of the product must be such that when the earth connection is removed it still does not present a safety hazard, in accordance with the single fault requirements of the relevant safety standard. When the earth connection is broken, the most acute problem is likely to be the touch current or leakage current from the product's enclosure. Generally, the problem is solved by ensuring that the design of the power supply and associated circuitry limits this current to acceptable values, rather than by adding a second earth connection. Best Wishes, Jon Griver http://www.601help.com The Medical Device Developers' Guide to IEC 60601-1 > > Group, > > This is a general product safety question: > > In order to avoid test failures during a single fault condition where the > primary ground is removed, what design methods can be used to add a second > ground to the system so that a ground is still provided even during a > single fault condition of removing the primary ground? > > All responses are appreciated. > > Regards > > Joe Martin > EMC/Product Safety Engineer > Applied Biosystems > marti...@appliedbiosystems.com > > > > > ------------------------------------------- > 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: > http://www.rcic.com/ click on "Virtual Conference Hall," > > ------------------------------------------- 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: http://www.rcic.com/ click on "Virtual Conference Hall,"
