I’ve changed the subject line because this discussion has strayed from the original question.
At retail rates (e.g. price per foot from lower.com) #6 wire is 89 cents per foot, and #12 wire is 8.2 cents per foot; assuming Clay’s 50 foot run and 3 wires for a 110 VAC circuit with ground, per NEC, the added cost for wire would be $121.20. Is it “good engineering practice?” It seems to be to be OK from an electrical standpoint, albeit unnecessary, and unnecessary from a cost standpoint, albeit not harmful. I can certainly understand “over-specifying” wire size in a 12 volt circuit, and using larger wire size than is required simply from considering ampacity, because the voltage drop is a much larger change proportionally, but I really don’t see the benefit from the expense and added installation difficulty of using larger-than-required wire for a 120VAC supply circuit. according to the online calculator at http://www.southwire.com/support/voltage-drop-calculator.htm, which takes into account both resistance and reactance of the wire: — for a 50 foot run of cable of #6 wire, at 20 amps and 120 volts AC single phase, the total voltage drop will be 0.884 volt, or 0.74%, for a net voltage at the end of the circuit of 119.1 volts (rounding) — for the same run with #12 wire, the total voltage drop will be 3.472 volts, or 2.90 percent, for a net voltage at the end of the circuit of 116.5 volts (rounding). The 3.47 volt drop would be intolerable in a 12 volt circuit providing power directly to amateur radio equipment, but seems to me irrelevant if feeding a competently-designed power supply that reduces the 120 volts AC supply to some lower voltage of DC supply. Any ham radio power supply that is specified to operate on 120 VAC should be able to operate without difficulty from a 116.5 volts supply. So, why go to the extra expense of #6 wire? While it seems to me to be to be harmless to “over-spec” the wire size, it also seems expensive and not necessary either per requirements of Section of 310-15 of the NEC or from a “good operating practices” perspective. Lew N6LEW > On Aug 11, 2016, at 11:12 AM, Kevin - K4VD <ke...@k4vd.net> wrote: > > The added cost of a 3x over-build seems like it would be awfully high. Is > this good engineering practice (seriously, I don't know)? > > Kevin K4VD > > On Thu, Aug 11, 2016 at 12:38 PM, Clay Autery <caut...@montac.com > <mailto:caut...@montac.com>> wrote: > >> How do you define "necessary". >> >> Paraphrasing K9YC, Jim.... "Big wire is your friend". >> >> I agree... >> >> I typically use wire at least 2 sizes larger than "required".... Often >> the wire size is determined by how big of a wire I can FIT in the >> application and how much money I can part with at the time. >> >> For instance, on my current power project... I am running 6 AWG x 4 from >> the service to the sub-panel @ 50 foot run for a 60 Amp separately >> derived service where there'll never be more than about a 20 Amp total >> demand... >> >> From the sub-panel to the receptacles about 3-1/2 feet below, I am using >> 10 AWG.... only because that's the largest wire the receptacle >> terminals are rated for. >> >> From the receptacles to all equipment, minimum 10 AWG... >> >> Bigger and shorter the wire, the better... >> >> ______________________ >> Clay Autery, KY5G >> MONTAC Enterprises >> (318) 518-1389 >> >> On 8/11/2016 10:43 AM, Ronnie Hull wrote: >>> Is 10 gauge necessary? >>> >>> Sent from my iPhone >> ______________________________________________________________ >> 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 ke...@k4vd.net <mailto:ke...@k4vd.net> >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > <http://mailman.qth.net/mailman/listinfo/elecraft> > Help: http://mailman.qth.net/mmfaq.htm <http://mailman.qth.net/mmfaq.htm> > Post: mailto:Elecraft@mailman.qth.net <mailto:Elecraft@mailman.qth.net> > > This list hosted by: http://www.qsl.net <http://www.qsl.net/> > Please help support this email list: http://www.qsl.net/donate.html > <http://www.qsl.net/donate.html> > Message delivered to l...@n6lew.us <mailto:l...@n6lew.us> Lew Phelps N6LEW Pasadena, CA DM04wd Elecraft K3-10 / KXV144 / XV432 Yaesu FT-7800 l...@n6lew.us www.n6lew.us Generalized Law of Entropy: Sooner or later, everything that has been put together will fall apart. ______________________________________________________________ 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