In the spirit of trying the simplest thing first, I'll swap the light switch out for a new one and see what happens.
Thanks for the tip, Jim -----Original Message----- From: Robert Macy [mailto:m...@california.com] Sent: Monday, July 10, 2000 12:49 PM To: Jim Eichner; emc-p...@majordomo.ieee.org Subject: Re: Are NTCs Safe to Use in Electrical Equipment-short life of light bulbs The subject of short life of light bulbs appears often on the alt.home.repair newsgroup. People come up with potential sources of problems like "on the same branch with the sump pump(or well pump)", and "long lines to the light bulb". Their solutions were to put in those dimmer switches that cause the light bulb to only get power at crossover "gently" turning them on. And "lower the voltage", and ... but the consensus of the true source of short lived light bulbs is "either a poor neutral termination or the light switch needs to be replaced!" I thought this a suspect answer until after this experience. My bathroom fixture took out light bulbs at the rate of about 1 per month, but that made sense with the concentration of heat inside its housing and with the ON/OFF cycling it is subjected to. Then one day the switch jammed up and had to be replaced. After that replacement, the fixture will keep bulbs for almost a year. Evidently, the "bouncing" contacts really do a trip on the cold filaments. You might be right in that an NTC (Negative Temperature Coefficient Resistor) will make up for it. But it hardly seems worth the effort. (Plus if it's not the switch, a potential of a poor neutral could really mean a major problem in your system. ) - Robert - Robert A. Macy, PE m...@california.com 408 286 3985 fx 408 297 9121 AJM International Electronics Consultants 619 North First St, San Jose, CA 95112 -----Original Message----- From: Jim Eichner <jim.eich...@xantrex.com> To: emc-p...@majordomo.ieee.org <emc-p...@majordomo.ieee.org> List-Post: emc-pstc@listserv.ieee.org Date: Monday, July 10, 2000 12:22 PM Subject: RE: Are NTCs Safe to Use in Electrical Equipment > >On the subject of NTC's, please allow me a slight detour from the compliance >world to the real world. > >I have a circuit in my house that blows light bulbs far more often than any >other. I can't determine any reason for this - the voltage seems normal and >there aren't any transient-producers on that same circuit (that I'm aware >of). Long life and rural-duty bulbs make little or no difference. > >Instead of figuring out the root cause, I'm considering resorting to trying >to deal with the symptom (blown bulbs) by putting an NTC in series with the >light fixture somewhere. My thinking is that the mechanism that blows an >incandescent bulb filament is related to the high inrush current into the >cold (and therefore low R) filament, and the physical and thermal stresses >that that inrush causes. > >Any comments on how likely this is to help, and whether or not I can safely >put an NTC in an junction box full of wires? I'd check the NTC's >temperature under load (they get hot) and compare that the the temp. rating >of the wires in the box. I'd also insulate the bare legs of the NTC and try >to make sure it isn't touching anything else. Anyone familiar with the >failure modes of these things? > >Thanks, > >Jim > >-----Original Message----- >From: Peter Merguerian [mailto:pmerguer...@itl.co.il] >Sent: Monday, July 10, 2000 7:58 AM >To: emc-p...@majordomo.ieee.org >Subject: Are NTCs Safe to Use in Electrical Equipment > > > >Dear All, > >I have seen some design where NTCs are used to limit inrush currents in >motion controllers. > >Q. Are NTCs safe and reliable as means to limit inrush currents? > >Q. Are there safety considerations to consider for circuits employing NTCs? > >Q. Are there any Approved (previously evaluated) NTC components out there? > > >I appreciate all of your comments and/or links regarding the use of NTCs in >electrical equipment. > >Thanks > >Peter Merguerian >Managing Director >Product Testing Division >I.T.L. (Product Testing) Ltd. >Hacharoshet 26, POB 211 >Or Yehuda 60251, Israel > >Tel: 972-3-5339022 Fax: 972-3-5339019 >e-mail: pmerguer...@itl.co.il >website: http://www.itl.co.il > > > > > > >------------------------------------------- >This message is from the IEEE EMC Society Product Safety >Technical Committee emc-pstc discussion list. > >To cancel your subscription, send mail to: > majord...@ieee.org >with the single line: > unsubscribe emc-pstc > >For help, send mail to the list administrators: > Jim Bacher: jim_bac...@mail.monarch.com > Michael Garretson: pstc_ad...@garretson.org > >For policy questions, send mail to: > Richard Nute: ri...@ieee.org > > >------------------------------------------- >This message is from the IEEE EMC Society Product Safety >Technical Committee emc-pstc discussion list. > >To cancel your subscription, send mail to: > majord...@ieee.org >with the single line: > unsubscribe emc-pstc > >For help, send mail to the list administrators: > Jim Bacher: jim_bac...@mail.monarch.com > Michael Garretson: pstc_ad...@garretson.org > >For policy questions, send mail to: > Richard Nute: ri...@ieee.org > > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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