Sorry, auto spell correct got in the way. That should have read “lowes.com”
lew > On Aug 11, 2016, at 12:03 PM, Lewis Phelps <[email protected]> wrote: > > 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 <http://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 > <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 <[email protected] >> <mailto:[email protected]>> 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 <[email protected] >> <mailto:[email protected]>> 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 >>> <http://mailman.qth.net/mailman/listinfo/elecraft> >>> Help: http://mailman.qth.net/mmfaq.htm <http://mailman.qth.net/mmfaq.htm> >>> Post: mailto:[email protected] <mailto:[email protected]> >>> >>> 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 [email protected] <mailto:[email protected]> >>> >> ______________________________________________________________ >> 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:[email protected] <mailto:[email protected]> >> >> 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 [email protected] <mailto:[email protected]> > Lew Phelps N6LEW > Pasadena, CA DM04wd > Elecraft K3-10 / KXV144 / XV432 > Yaesu FT-7800 > [email protected] <mailto:[email protected]> > www.n6lew.us <http://www.n6lew.us/> > > Generalized Law of Entropy: Sooner or later, everything that has been put > together will fall apart. > > > > > Lew Phelps N6LEW Pasadena, CA DM04wd Elecraft K3-10 / KXV144 / XV432 Yaesu FT-7800 [email protected] 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:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
