> We have a product for non-residential use that is powered by a line > frequency a.c. power pack. With a 230 V a.c. power pack, the product has > been tested by a NATA accredited laboratory and meets EN55022: 1995 Class > A. > > If we source a UL approved 115 V a.c. power pack, is it necessary to have > the product re-tested for EMI with the new power pack for sale in the USA?
The FCC's position on this matter is very clear. The FCC considers the total unit, including the power supply, to be the Equipment Under Test. The FCC rules state that compliance with CISPR 22 is an acceptable means to show compliance with the FCC. However, when testing to the CISPR 22 limits, the FCC test procedure, ANSI C63.4-1992, must be used. The testing must also be performed at the US line voltage, conducted emissions must be performed from 150 kHz to 30 MHz using both the QP and average limits (as per CISPR 22), and, if the unit uses or prduces a frequency above 108 MHz, radiated emissions testing must be performed up to the frequency specified by the FCC rules and using the FCC limit only for emissions above 1 GHz. It sounds like you will definitely need to retest the conducted emissions of the new power supply with your unit and you should probably rescan the radiated emissions to insure that the new power supply does not cause any unforseen problems. If you decide to perform all of tests again, you may decide to test to the FCC limits at 115 V. Finally, as of August 19, 1996, the FCC is implementing a program to separately approve power supplies and motherboards for Class B PC's. This program is currently in transition for power supplies until August 19, 1997 when it becomes mandatory. I know this product is a Class A device, but it may now be possible to purchase an FCC Class B approved power supply. Under this same rule change, the manufacturer/integrator is allowed to change the power supply, motherboard, I/O card, etc. in an approved FCC unit with an approved component (i.e., power supply) and not retest the unit. Please be aware that it has been an old practice of some power supply manuafacturers to advertize and place a sticker on their units (with the FCC logo) that states the units are FCC compliant. This is not necessarily the same as FCC approved. ==================================================== Ray Hammonds Tel: 301-417-0220 Chief EMC Engineer Fax: 301-417-9069 Washington Laboratories 7560 Lindbergh Drive Gaithersburg, MD 20879. USA
