12 ga. extension cords and 220 volts

I have two 12 ga extension cords, one is rated for 15 amps (???? they seem to be covering their buts with both hands) and 115 volts and the other just has a "20 amps" notation, no voltage rating seen.

At Home Chepo I see all their 12 ga cords are rated for 115 - 120 volts.

All my Romex wiring seems to be comfortable handling 600 volts (if I recall correctly).

Is this just because of the pattern and/or construction of the plug ends (and them covering the behinds for liability purposes), or is there a safty issue with running 220 volts through multi-strand copper 12 ga wire? All I can imagine is heat production which might melt the insulation.

Is 7 amps at 220 volts going to cause more heat than, say 13 amps at 115 volts?

All my Romex wiring seems to be comfortable handling 600 volts (if I recall correctly).

Thanks,
Tim

The cords were marked 15 amp because that is all a common 120v plug and receptacle is rated to, and thus becomes the limiting factor.

I have a 1hp Craftsman compressor, probably 35 years old, bought it new. When I built my shop it was a year before I got power on the building. For a year, a 100 ft long, 12 gauge, 120v extension cord lay in the yard running from an outlet on the back porch of the house out to the shop. That little Craftsman compressor shows something like 17 amps on the data plate, and it ran just fine on that cord, when it started the fluorescent trouble light also on the circuit would go out momentarily but I understood that, considering the amps I was drawing.

Charles

Buying air hose rather than extension cords surely is the way to go - at those distances the most I am planning to do is use a framing gun.

I posted that question before I left work last night, then stopped on the way home at LoweDown and checked out air hose. I did not realize how cheap it is.

Still, good information in those posts - stuff I can surely use next time I need to do some dangerous kind of gerryrigging.

$20 will get you 100 feet of hose, I'd go that route. Compressers don't like extention cords, they draw a lot of power to start up. Trips breakers real easy. Not sure you will find a 7 amp 240v breaker to protect that cord. ;)

--->Paul

Sufficiently large air hoses (to avoid excess pressure drop) is certainly one way to go.

yall take care now

John T

Home Depot sells bulk 12/3 cable rated at 300 volts. I made up an extension cord for my compressor and it works great. However, for the distance you want to run, 12/3 is marginal. It takes a LOT of current to start a loaded compressor. If you're going to use the extension cord a lot, I think I'd go for 10/3. For occasional use, 12/3 will be fine.

John T

You need 3 conductors, of course, the two hots and one safety equipment grounding conductor i.e. 12/3 or called 12/2 with ground.

The other issue is voltage drop but at only 7 amps load on 12 gauge conductors at 100 feet I dont forsee a problem but didnt run any calculations.

As far as how many watts of heat you dissipate over the entire cord, its I squared R but the R is fairly low on 12 gauge copper for 100 feet. Its also E x I (220 volts x 7 amps) so at twice the voltage and the same current it doubles, but the same motor only draws half as much current if the voltage doubles. BUTTTTT T the current rating of the cord is what the heat dissipation capacity is all about sooooo oooo if its rated 20 amps (depends on if in free air or conduit or whatever) then it can handle that current without exceeding the heat capacity of the insulation.

Have a plug n cord or other disconnect means at the motor of course and also of course current overload protection (proper sized breaker or fuze) back at the source to protect the feeders. The motor ought to have its own thermal overload to protect the motor itslef

John T Long retired n a bit rusty Electrical Engineer SO NO WARRANTY LOL

I entered "voltage drop calculator" on Google and got one that said that 12 gauge wire will carry 19 amps 100.4' with a maximum 3% voltage drop. When I entered 22.2 amps (7.4 X 3) it said that 12 gauge cannot carry 22.2 amps, not that it would carry it a shorter distance as I expected.

I'd be the world's biggest hypocrite if I cautioned you not to do something just because it was dangerous and foolhardy. Dangerous and Foolhardy is my middle name (actually it's Jameson.) I'm also sure that you're well aware of the potential insurance consequences you'd face if your insurance company ever heard you were doing something like that even in the same county where there was a fire. One thing I will mention though, is that you want to take a setup like that apart just as soon as you finish using it. Anything electrical that is jury rigged together is like a land mine waiting to blow up the next innocent person to touch it. Ask BuickandDeere his opinion of such a project if you want to encourage cursing that you will actually be able to hear all the way from central Canada.

All the best, Stan

God protects fools, drunks and little boys. Only thing thats kept me alive.