[TowerTalk] Wiring Sky Needle tower for 220 VAC
Grant Saviers
grants2 at pacbell.net
Tue Nov 5 19:29:42 EST 2013
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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