I believe that in the USA, the AC power feed is defined by the National Electrical Code (NEC). For Residential service, the utility company will supply a 120-0-120 three-wire feed to a house. At the point of entry, the "0" wire will be tied to a physical ground rod. The "0" wire, which we call Neutral, will then be routed to a distribution busbar in the circuit breaker panel of the house. Both of the "120" lines will route through the meter and then through the circuit breakers. Power for various loads is drawn from the individual breakers. A Safety Ground distribution busbar is also connected to the ground rod, and Safety Ground wires go from the distribution busbar to all (typically NEMA-15) outlets too.
For typical Class B FCC Residential equipment, the "high" side will connect to a circuit breaker output and the "low" or "return" side will connect back to the Neutral distribution busbar. So, if you are testing to FCC Part 15 for Class B, then I would say that your power source should have the Neutral tied to the Ground. And for justification, you can cite the NEC as governing the electrical interface where a Class B equipment would be utilized. Ed Price WB6WSN Chula Vista, CA USA -----Original Message----- From: John Woodgate [mailto:[email protected]] Sent: Wednesday, October 23, 2013 7:19 AM To: [email protected] Subject: Re: [PSES] AC input test voltages - requirement for grounded phase? In message < <mailto:camsb7hsnbuxus1fwguu9em2oo-vqjxvagdxqb8jnwbwpfo5...@mail.gmail.com> camsb7hsnbuxus1fwguu9em2oo-vqjxvagdxqb8jnwbwpfo5...@mail.gmail.com>, dated Wed, 23 Oct 2013, Pat Lawler < <mailto:[email protected]> [email protected]> writes: >Do the EMC test standards require one of the AC input phases ('neutral' >in the U.S.) be grounded? If so, where can I find an example of this >requirement? I can't recall any specific provision, but the testing must be done under conditions that are as realistic as possible, and a balanced mains supply does not qualify unless the product is specifically intended to be operated from such a supply. -- OOO - Own Opinions Only. With best wishes. See <http://www.jmwa.demon.co.uk> www.jmwa.demon.co.uk If dictionaries were correct, we would only need one, because they would all give the same information. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
