Over the last few years, our lab has seen GFCIs falsely trip during the radiated immunity test at 3V/m (don't recall frequency) and by conducted emissions caused by a motor speed controller (frequency drive). In the later case, fingers got pointed in all directions. If the GFCI trips for any reason other than high leakage or line imbalance then is it the fault of the GFCI? Are there GFCIs on the market that specifically designed for applications such as frequency drives where they are less susceptible to conducted emissions and line harmonics?
We know the NEC requires GFCIs to be used in bathrooms, basements, garages and on curtain products such as hair dryers, hot tubs and window air conditioners, but in the workplace, where are GFCIs absolutely required? Case in point, I know of a product which has a motorized spinning platform with sandpaper with water running on it (wet sanding). The frequency drive that runs the motor causes a GFCI to trip yet the product passes conducted emissions (class A) and leakage current test (about 1ma). Is the problem with the product or the GFCI? Does a GFCI have to be used with such a product? If so, are there alternate solutions to using a GFCI such as providing addition earth ground connections? Thanks. The Other Brian From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Thursday, July 19, 2007 8:41 AM To: [email protected] Subject: RE: Cell/mobile phones destroying electronic devices I have been doing some research over the past few months regarding the susceptibility of GFCIs and AFCIs to interference. I have yet to uncover any documented evidence of cellular telephones or other wireless devices interfering with these devices. Even with the large antennas of the wiring, it is difficult to couple enough energy to cause a problem. GFCIs and AFCIs are somewhat susceptible to conducted interference, but the designs have been greatly improved over the years. As a general rule, you don't want GFCIs and AFCIs in circuits for life safety applications. They should not be used for fire alarm systems, fire pump systems or emergency lighting. These devices should definitely be avoided for any application where a power interruption will cause significant financial harm or put lives at risk. As Doug Smith noted, Information Technology Equipment (ITE) should not be used on GFCI circuits. IEC 60950-1 allows an ITE device with a non-locking plug to have an earth leakage current of up to 3.5 mA. A GFCI in North America is set to trip at around 5 mA. If you plug in your computer, monitor, printer, scanner, cell phone charger and cordless phone base into a power strip on a GFCI protected circuit, you may easily find it tripping regularly. AFCIs work differently, but they too can be very susceptible to conducted noise from ITE. I have worked with some that are well tested for immunity to conducted noise and some which regularly trip in ITE environments. In the interest of full disclosure, I will note that APC is a subsidiary of Schneider Electric which also owns Square-D. I am aware of extensive testing of the Square-D devices for conducted immunity and they are not among the devices for which I have found problems. 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. "Tarver, Peter" <peter.tarver@san mina-sci.com> To Sent by: <[email protected]> [email protected] cc Subject 07/18/2007 05:06 RE: Cell/mobile phones destroying PM electronic devices All - In a similar vein to this thread, in January of this year, I posted a request for information regarding wireless phones interfering with GFCI devices. This same request was also posted on the EMC-PSTC and Electrical Safety IEEE Community pages, in order to broaden the audience and to alleviate one expressed concern regarding the confidentiality statement that (no doubt) appears at the bottom of this e-mail. Unfortunately, there's been no responses that I'm aware of. I've duplicated that request, below. Any input would be appreciate. If there is a concern about passing the information through me, I can put anyone interested in responding in touch with the appropriate staff at the TIA. ***ORIGINAL REQUEST*** The TIA (Telecommunication Industry Association) is looking for any information on incidents of wireless phones (cordless, cell, etc.) interfering with ground fault circuit interrupters (GFCIs). If anyone has any information relating to this, please let me know and I will forward information to the interested group. Regards, Peter L. 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