Wires, Extension Cords and other Transmission Lines
by Bryan A. Thompson
Last Updated 2/10/2003
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Using Extension cords alone
If you've ever strung extension cords through the house during a blackout, you know how much this sucks. It takes a long time to unplug everything, string the extension cords and power strips and plug in everything, and since the power is out, it's usually all done in the dark. When the power comes back on, it takes even longer to dismantle the makeshift distribution system put everything back the way it was. The time this takes makes it impractical to do unless the blackout lasts for a really long time, so you're more likely not to use it at all.
Extension cords and the Emergency Power Distribution System
The Emergency Power Distribution System is my attempt to make the process of switching loads from grid power (when available) to an alternate power source (a generator or UPS), and then put it all back the way it was when grid power returns.
The EPDS consists of an alternate power source, a Honda EU2000i generator, a centralized distribution box which prioritizes loads and distributes power to them accordingly, and several wall switch boxes which sequentially switch the load from grid power to alternate power during a blackout.
Another vital part of the Emergency Power Distribution System is the conductors which connect the generator to the distribution box and the distribution box to the multiple wall switch boxes. Since I live in an apartment, I can't very well rewire, so I use extension cords. I use a 10ga cord between the generator and distribution box, and 12ga cords between the distribution box and the three wall switch boxes. All cords are as short as possible and as large as I could afford, and I estimate that these consume about 100W at their rated current - that's 7 percent of my generator output, just to get the power to where it's needed!
The cords are installed permanently everywhere that they can be. In the cases where extension cords are permanently installed, I used black cords and ran them along baseboards to camouflage their presence from a less-than-understanding landlord. The other cords are installed when blackouts happen. I have installed screw-in hooks over doorways to keep these cords out of the way while they're installed.
Wire Resistivity, Voltage Drop and Power Loss
These are my notes on wire resistivity, voltage drop and power loss for common wire sizes. This can help you to calculate the size extension cord to buy and the voltage drop and power loss to expect.
Note: Some of the information contained here was found from unknown sources on the Internet, and should be considered completely unreliable!