Re: [TowerTalk] Wiring Sky Needle tower for 220 VAC

[Grant Saviers <grants2@pacbell.net>]

You are correct that ampacity is a maximum current rating.  #6 Al is 
0.81 ohms/kft and #10 Cu is 1.29 ohms/kft so there is a substantial 
difference in DC resistance indicated by the ampacity ratings (40 amps 
#10 Cu vs 60 amps #6 Al THHN direct burial).  1/3 less voltage drop for 
motor starting (about the same for AC Z).  Can't beat free though.
Grant KZ1W


On 11/5/2013 11:49 AM, Richard (Rick) Karlquist wrote:
> On 11/5/2013 11:32 AM, Grant Saviers wrote:
> > Another alternative is the Home Depot 6/4 aluminum cable, when I bought
> > 165' for a 50amp  construction drop they called it "hot tub wire". About
> > a buck a foot, so more ampacity than #10 Cu at lower cost and ok for
> > direct burial.
> >
> > Grant KZ1W
> The problem with the US Tower motor is that it draws 20A plus
> a surge when you start and the relays drop out if you get much below 
> 120V.  "Ampacity" refers to what the wire can carry without 
> overheating, but on  a long run like 250 feet, you need much heavier 
> wire than what ampacity would dictate.  My tower would only operate
> on cool days, it was that close to not working.
>
> I happened to get my 250 foot 4 by #10 extension cord for nothing.
> I would never actually buy something like that new.
>
> Rick N6RK
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