I think it was shared neutral. The cubicle wiring design could well have been from before 1979.
On the other hand, one of the graphics boxes for the HP 300 series had two power supplies with two power cords, so we were pushing the cubicle wiring pretty hard. wunder K6WRU Walter Underwood CM87wj http://observer.wunderwood.org/ (my blog) > On Aug 11, 2016, at 2:18 PM, Matt Zilmer <mzil...@roadrunner.com> wrote: > > Was this a "shared neutral" type of problem? I thought NEC ruled that out in > post-1979 wiring plans. > > 73, > > matt W6NIA > > > On 8/11/2016 2:10 PM, Walter Underwood wrote: >> In the late 1980’s, we had some cubicle wiring fires at HP Labs caused by >> computer power supplies. They had to replace all the wiring with bigger >> conductors and connectors for the neutral. The same thing happened with >> Project Athena at MIT. >> >> wunder >> K6WRU >> Walter Underwood >> wun...@wunderwood.org >> http://observer.wunderwood.org/ (my blog) >> >> >>> On Aug 11, 2016, at 1:09 PM, Jim Brown <j...@audiosystemsgroup.com> wrote: >>> >>> On Thu,8/11/2016 12:03 PM, Lewis Phelps wrote: >>>> So, why go to the extra expense of #6 wire? >>> All the calculators assume sinusoidal current (i.e., a perfect 60 Hz sine >>> wave). That's not the real world -- only un-controlled heating elements >>> draw sine wave current. For at least the past 30+ years, electronic loads >>> dominate, and the what's connected to the power line is a >>> transformer-rectifier-capacitor power supply, and now usually as the input >>> to an SMPS. The line current drawn by such a supply takes the form of short >>> pulses at positive and negative peaks of the 60 Hz waveform, so both IR >>> drop and dissipation is much greater than predicted by simple sine wave >>> analysis. None of this is taken into account by NEC. >>> >>> Thus, it IS good engineering practice to oversize AC conductors. >>> >>> There's a tutorial discussion of this in >>> >>> http://k9yc.com/GroundingAndAudio.pdf >>> >>> 73, Jim K9YC >>> >>> ______________________________________________________________ >>> Elecraft mailing list >>> Home: http://mailman.qth.net/mailman/listinfo/elecraft >>> Help: http://mailman.qth.net/mmfaq.htm >>> Post: mailto:Elecraft@mailman.qth.net >>> >>> This list hosted by: http://www.qsl.net >>> Please help support this email list: http://www.qsl.net/donate.html >>> Message delivered to wun...@wunderwood.org >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Elecraft@mailman.qth.net >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to mzil...@roadrunner.com > > -- > Always store beer in a dark place. - R. Heinlein > > Matt Zilmer, W6NIA > [Shiraz] > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to wun...@wunderwood.org ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
