As I understand things (in my American-centric world), a GFCI duplex outlet protector contains a toroidal core that senses the differential current between the Hot and Neutral conductors. The magnetic field is pretty well-contained within that toroid core. Electric fields are dependent of the applied voltage and the physical structure of the conductors, but I don’t think there any reason to expect E-fields from a GFCI to be any different than E-fields from a standard duplex outlet. Also, the GFCI duplex outlet protector only senses differential current (which it assumes is attributable to a ground fault); it does not sense load current nor does it trip to open the circuit due to current overload.
A typical 1-pole circuit breaker (in a home distribution box) senses load current and opens the circuit due to an overload. It uses two methods of current sensing, thermal and electromagnetic. The thermal sensing consists of a bimetallic leaf that carries the load current, experiences Ohmic heating and applies a force to a trip mechanism. The electromagnetic sensing consists of a solenoid coil that carries the load current, a straight cylindrical core and a lever that also exerts force on the trip mechanism. The thermal system is aimed at sensing long-term loads while the electromagnetic system is aimed at sensing short-term loads. As the thermal system deliberately generates heat, the breaker case will run a bit warm. As the electromagnet system uses an open, cylindrical core, it will create a non-uniform magnetic field. I have never tried to measure this field, but insects sensitive to magnetic fields would certainly sense the magnetic field around a loaded circuit breaker. (Perhaps some circuit breakers have shielded cases, but I have never seen anything other than plastic.) That’s a basic circuit breaker; they get more complicated with incorporating GFCI and AFCI sensing directly in the breaker. However, I’m speculating that the major H-field contribution comes from that solenoid current sensing subsystem. And that’s about all I know about shrimp, I mean GFCI’s. Ed Price WB6WSN Chula Vista, CA USA From: John Woodgate [mailto:[email protected]] Sent: Thursday, September 15, 2016 5:42 AM To: [email protected] Subject: Re: [PSES] Fire ants Does a GFCI also produce stronger electric fields than occur in other boxes? But magnetic field sensitivity is quite possibly the explanation. With best wishes DESIGN IT IN! OOO – Own Opinions Only <http://www.jmwa.demon.co.uk/> www.jmwa.demon.co.uk J M Woodgate and Associates Rayleigh England Sylvae in aeternum manent. From: IEEE [mailto:[email protected]] Sent: Thursday, September 15, 2016 1:25 PM To: [email protected] Subject: Re: [PSES] Fire ants I wonder if there are any entomologists that are studying this effect? Has anyone looked up any of the ant specialists to see if they’ve been exploring this phenomena? WRT to Don’s experience, I wonder if it’s the magnetic field that is attracting them more than the electric field? The GFCI has some toroidal current transformers that might be part of the attraction… I was also wondering if the abdominal signalling/pheromone release behaviour following the electric shock was a call to battle with a perceived enemy, against which they could not win. I guess if you pile on enough dead ants you can eventually trip the breaker feeding the circuit, and the ants “win”, at least in the moment. Anyway, sounds like we need some bug guys involved in this discussion… Doug Nix [email protected] +1 (519) 729-5704 On Sep 15, 2016, at 06:14, Gies, Don (Nokia - US) <[email protected]> wrote: Yes. I had a GFCI 20A circuit breaker in my panel feeding my pool pump motor. I went to open my pool last spring and the breaker kept tripping. So, I concluded that the breaker went bad. I opened up the breaker panel to change the breaker and found that the GFCI breaker was infested with ants (regular ones, not fire ants), but interestingly, the GFCI breaker was the ONLY breaker in the entire panel that had ants. DON GIES NOKIA Bell Labs SENIOR PRODUCT COMPLIANCE ENGINEER GLOBAL PRODUCT COMPLIANCE LABORATORY 600-700 Mountain Avenue Room 5B-104 Murray Hill, NJ 07974-0636 USA Phone: +1 908 582 5978 Mobile: +1 732 207 7828 <mailto:[email protected]> [email protected] From: Doug Powell [mailto:[email protected]] Sent: Wednesday, September 14, 2016 6:04 PM To: [email protected] Subject: [PSES] Fire ants All, I was wondering if anyone has any real experiences with fire ant infestation in electrical equipment that they would be willing to share. <http://articles.extension.org/pages/30057/ants-and-electrical-equipment> http://articles.extension.org/pages/30057/ants-and-electrical-equipment It seems to me that for high current contractors and electrical disconnects (not using self-wiping contacts) with contaminants between connection points can result in resistive connections, I^2R heating, potential arcing and if enough voltage is present, series arc faults which over time can erode connections and result in a fire. Does anyone have experience with this as a real problem? Thanks Doug -- Douglas E Powell <mailto:[email protected]> [email protected] <http://www.linkedin.com/in/dougp01> http://www.linkedin.com/in/dougp01 - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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