> RussellMc writes: >> Be absolutely certain that the contacts are rated to handle the maximum >> AC >> voltage that will be encountered. >> >> The AC load spec is almost always far more stringent than the DC load >> spec >> and failure to note this can cause relay failure at well below apparent >> rated (DC) value. >> >> >> >> Russell > > Now, I am curious. Why would the AC load spec be more > stringent? It would seem to me that DC conditions would be worse > since the flow of current is always at it's peak unless one is > closing the contacts on an inductive load at which point it would > be less current while the field was building in the inductor. When > the contacts opened, there could be a nasty arc if the inductor > had built up enough magnetic field. > > In AC, you sort of roll the dice and the contacts could > sometimes open or close right at a 0 crossing and nothing much > would happen as far as sparks or spikes. The peak voltage, > assuming a sine wave, would be roughly 1.4 times the RMS voltage. > > What am I missing? > > Martin McCormick WB5AGZ Also with an AC load, you get an arc quench every half cycle that you don't get with DC. Choosing a random relay from Mouser: https://www.mouser.com/datasheet/2/307/en-g5le-1131193.pdf Rated load Resistive: 10 A at 120 VAC; 8 A at 30 VDC Inductive: 5 A at 120 VAC; 4 A at 30 VDC Harold --=20 FCC Rules Updated Daily at http://www.hallikainen.com Not sent from an iPhone. --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .