"Dan Krueger" wrote in message
ink.net...
CalifBill wrote:

"Jack Goff" wrote in message
...

On Sat, 08 Apr 2006 00:54:50 GMT, Dan Krueger
wrote:


John Wentworth wrote:

"Mys Terry" wrote in message
om...


The distance in this case is a pretty important factor. I don't think
a 15 amp "tool" is going to be very happy on a 100 foot 12 gauge cord.



You're correct. To have a not greater than 3% voltage drop, a 15 amp
load
on a 100 foot cable would require #8 wire.
See http://www.elec-toolbox.com/calculators/voltdrop.htm for a voltage
drop
calculator.



Contractors use 100' 12ga extension cords every day to power large saws,
rotary hammer drills, and other big tools powered by their generators.
10ga or bigger would be expensive, hard to find, and not necessary.

Dan

Exactly correct. The calculator referenced only allows a 3% voltage
drop, which is only 3.6V for a nominal 120V ac circuit. Maybe if
you're running sensitive medical equipment that's necessary, but not
for power tools. A 15 amp circular hand saw is perfectly "happy"
running on 105V or so, over a 10% drop.

Think of it this way... your home wiring is usually 14ga for normal 15
amp branch circuits. Not unusual to have a 100ft run between the
breaker box and the outlets. Some voltage drop is expected, and
safety factors are built into everything you buy.

Jack



15 amp circuits are 14 gauge, and few run 100' inside a house. More like
50' at most. Contractors use 12 gauge because you can move the cord.
And most saws and tools are built to run in a 15 amp circuit, not draw 15
amps. Most are in the 7-8 amp range.

I think you are mistaken. 12 ga cords are heavier than 14 ga. Also,
anything with an electric motor will draw more power when you start it and
have it under a load than when it's running without a load. I have never
seen a standard 7-1/4" circular that would start and cut while drawing
only 8 amps. Most are rate at 12+ amps.

Dan

I say a 12 ga, which is normally a 20 amp circuit, because anything larger
is a real pain to move. Most saws will draw a lot less than 15 amps. My
Sil Mag 77 is rated 13 amps, and that is probably with the blade jammed or
near jammed.