Hello Joel, The ground connection is treated differently from other terminals because of what happens if it fails.
If a line connection comes loose, there should be some indication of a problem. The equipment will likely not operate properly or it will operate at a reduced capacity of some type. The earthed chassis of Class I equipment, or the double insulation of Class II equipment will protect the user from this failure. The indication of the problem should prompt the user to remove the product from service for repair. I realize that this doesn't always happen, but at least the user has been given some indication that there is a problem and it is now up to them to take action. If a ground connection fails, there will be no indication of a problem to the user. The product will likely continue to operate perfectly normally. A second failure, such as a loose line wire, could lead to the sudden and unexpected energizing of exposed metal. The product has now become hazardous without warning. I know that this is a generalization and we don't live in an ideal world. However, it is based on the concept of risk reduction. Adding a supplementary retention method to a ground connection can provide an additional level of safety. Ted Eckert American Power Conversion/MGE http://www.apc.com/ The items contained in this e-mail reflect the personal opinions of the writer and are only provided for the assistance of the reader. The writer is not speaking in an official capacity for APC-MGE or Schneider Electric. The speaker does not represent APC-MGE's or Schneider Electric's official position on any matter. Joel Sandberg <jbsandtech@yahoo .com> To Sent by: emc-p...@ieee.org emc-p...@ieee.org cc Subject 03/16/2008 09:36 Protective Earthing Terminal PM Construction Requirements To Members of the Product Safety Group; I am trying to find the construction requirements, and the standards that set these requirements, for a protective earth(ing) terminal. Many of us have learned that there needs to be locking washers and nuts between each ring lug. But where is this actually called out and required? I am trying to show the engineering department were I work which parts of this "good practice" are actually requirements of the requirements we will be claiming to meet. I have found a diagram at www.phihong/html/grounding.html (Phihong.com) that shows reasonable grounding technique. But this web site does not site any standard as a basis for the technique. I have searched 60601-1:1988 and 60950:95 looking for requirements and a diagram. I have found resistance requirements, 0.1 ohm max in 60601-1, section 18 f), but I can not find construction explicit requirements. Does anyone know if any standard includes explicit construction requirements for a protective earth terminal and for connections to a PE terminal? Thank you. Joel Sandberg Lake Worth, FL Looking for last minute shopping deals? Find them fast with Yahoo! Search. - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
