Robert Know that even UL Certified extension cords are for temporary use only. They are not to be plugged into an appliance and left undisturbed for a long period of time.
Greg Nielsen Compliance Engineer Set Engineering, Inc. -----Original Message----- From: Robert Macy [mailto:[email protected]] Sent: Thursday, October 25, 2001 2:30 PM To: Jim Eichner; [email protected] Subject: Re: skinny power cords. Yes, I believe it was contamination. There is a tissue box on the night stand above the outlet. Tissue lint is insidious. The extension cord had been plugged in (AND LEFT UNDISTURBED) for a long period of time. Exactly, how the buildup made its way to an inside surface I don't know. But remember, an experienced fireman related that this is how most electrical fires start in his experience - an outlet shorts between blades (or in that area), the breaker does not trip while the arc is sustained, flames develop, and great damage occurs. I was upset that the 15A breaker could care less about the arc sizzling at the outlet. The reason I mention the extension cord is to point out that the plug plugged into the outlet was high quality and not a "cheap" lamp cord of suspect origin. Yet, this plug still carbonized AND FLAMED! making things much worse. Now, I do maintenance around our home using compressed air can to blow the outlet box clear of everything and unplug everything and wipe all surfaces clean. This has worked, but may not always, since sprays etc used in the area tend to produce a gummy, waxlike deposit on the outlet and there still may be stuff down inside. - Robert - Robert A. Macy, PE [email protected] 408 286 3985 fx 408 297 9121 AJM International Electronics Consultants 619 North First St, San Jose, CA 95112 -----Original Message----- From: Jim Eichner <[email protected]> To: [email protected] <[email protected]> List-Post: [email protected] Date: Thursday, October 25, 2001 12:07 PM Subject: RE: skinny power cords. > >I'm curious: given that North American plug blades are >1/2" apart, there >must have been substantial contamination to aid in 120Vac jumping that far >(arcing). Did you identify any sort of contamination or moisture? > >Jim Eichner, P.Eng. >Manager, Engineering Services >Xantrex Technology Inc. >Mobile Power >phone: (604) 422-2546 >fax: (604) 420-1591 >e-mail: [email protected] >web: www.xantrex.com > > >-----Original Message----- >From: Robert Macy [mailto:[email protected]] >Sent: Thursday, October 25, 2001 8:50 AM >To: Roman, Dan; [email protected] >Subject: Re: skinny power cords. > > > >Just have to jump in here with personal experience: > >In our bedroom we have a deLonghi radiator heater which uses an extension >cord (high cost UL approved) heavy guage #12 wire to power it - when it's >used. This extension cord plugs into a "multi outlet" adapter, also heavy >duty UL approved. At the time of the incident there was no power being used >from this outlet. > >I was in another room, my wife was sitting on the edge of the bed watching a >news blurb on TV when she heard a funny sound, a scritch, scritch. She >called to me to come listen. Scritch, scritch, scritch got louder. As I >arrived, flames started lapping up the wall from the outlet while still >making arcing sounds. The flames were less than 6 inches from curtains. I >reached into all this and unplugged the extension cord which luckily stopped >the fireworks display. Imagine, if we had not been there. > >Upon examination, it appeared that an arc had formed between the blades of >the extension cord (remember no power at the time). That arc was not >sufficient to drop the 15A breaker to the outlet, yet was sufficient to >carbonize the UL approved material which further sustained the arc. > >I posted this to the newsgroup alt.home.repair where a fireman jumped in >describing how this exact mechanism is what starts most home fires! Isn't >that an encouraging thought! > >Anyway, a little damn fuse in the plug would not have helped in this >circumstance, complete waste of time, much like the main breaker was. > > - Robert - > > Robert A. Macy, PE [email protected] > 408 286 3985 fx 408 297 9121 > AJM International Electronics Consultants > 619 North First St, San Jose, CA 95112 > >-----Original Message----- >From: Roman, Dan <[email protected]> >To: [email protected] <[email protected]> >Date: Thursday, October 25, 2001 7:41 AM >Subject: RE: skinny power cords. > > >> >>I agreed completely with Scott. A 6 to 9 foot 18AWG cord will handle well >>in excess of 20A for a short period of time without starting to smoke >(heck, >>it'll handle close to in excess of 60A for a very very short time without >>bursting into flames--not that it was a good experience finding this out). >>Point is, the cordage will handle a fault either indefinitely or long >enough >>for the branch circuit breaker to trip provided you are connected to a 15A >>or 20A branch circuit. >> >>Another data point, you routinely pass more current through the cord when >>doing the earthing test and that uses more current than the cord is rated. >>Leave the tester on for awhile and the cord does not really heat up either. >> >>What this list needs is a power cord manufacturer or agency safety engineer >>that does power cords to settle this once and for all! >> >>Dan >> >>-----Original Message----- >>From: Scott Lacey [mailto:[email protected]] >>Sent: Wednesday, October 24, 2001 7:43 PM >>To: Gary McInturff >>Cc: [email protected] >>Subject: RE: skinny power cords. >> >> >> >>Gary, >>I believe the answer is that the power cord rating of 6 or 10 amps is the >>operating current, at which it will have minimum temperature rise. Under >>fault conditions it will experience a rather dramatic temperature rise that >>is still well below the melting temperature of the insulation. The breaker >>or fuse should clear well before the cord is "cooked" to the point of >>failure. >> >>Scott Lacey >> > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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