Is there a formula for calculating the power lost when using extremely long extension cords?

An 18ga copper wire will have a resistance of about 6.4ohms per 1000ft. You can figure out how much voltage you will lose using the E=IR formula (voltage drop = current * resistance). remember that the wire distance is twice the length of the cord because the current has to go both ways - out and back.

If the drop is 5v, your device would be trying to run on 105v vs 110v. Lower voltage will deliver less current to your device.

See http://www.powerstream.com/Wire_Size.htm for more info. It has a pretty cool voltage drop calculator

Extension Cord Calculator

Yes it will work to use a extension cord. But its not the proper installation. You should not run extension cords in attics, and they are designed for temp. use. The exhaust fan designed to be hard wired. With that said, make sure you check the Load on the exhaust fan,(AMPS) If the amps are less than 10 you can use a #14cord, if its 10-16amps use a #12 cord. The length of the cord is very important, you should use as short of a cord as you can. the longer the cord, the bigger the wire of the cord needs to be. Hope this helps

you want better wire for 900 feet.

first you need to compute for your voltage drop in order to compute your power line losses.

go here:http://www.neccode.com/freestuff.php?id=freegenera...