Electricians? Anyone know how long a chain of extension cords can be?

Extension cords can get pretty darn long. I don't see a problem with this.

Prawn, I agree with JoNightshade. Your extension cords connected together won't be a problem. Just make sure they're all plugged in tightly together.

But wow, several hundred yards long? That's pretty long, but not implausible by any means. It'll be a bitch later to take them all down and coil them all back up. (What am I saying? This is a book!)

allen

And now you can plausibly have the whole place burst into flames. That's always exciting.

several miles. but not as many kilometers.

One or two of these should do it:

http://www.amazon.com/dp/B0000225BA/?tag=absolutewritedm-20

Prawn said:

In my WIP, I have a thick, industrial extension cord going off a third floor balcony, and down into a basement, then into a passage several hundred yards long.

Is their a limit to over how long a distance you can chain extension cords together?

Batteries won't work, they need a lot of power to run something like a compressor, but I don't want to put in something that is impossible. Implausible I don't mind.

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It's not impossible, but could be implausible. Variables are the length of the cord (longer is worse), the size of the elecrical conductors in the cord (larger is better), and the number of cords (each plug/mechanical connection is a source of resistance, more is bad). You can (or you could years ago) get 100-foot extension cords at Home Depot, good for things such as electic lawn mowers (I think someone still makes them). A compressor could probably run on a few strung together, but the more there are, the greater the voltage drop in the cord, and the less likely the compressor will start up (it uses much more current when it starts up than when it's running). Also, if it does run, running it on reduced voltage could cause it to overheat (electric motors are funny about that - LESS voltage can make them use MORE power, and turn it into heat).

Here's a scenario: they have two things plugged into the end of the cord: a 100 watt lightbulb and the compressor. The light is on, and the compressor is turned on. The light goes to about half brightness, and the compressor hums and groans but doesn't start running. Someone who knows something about electricity sees what's happening, and knows the light is pulling power too. If it's turned off, there's a little more power for the compressor, and it's more likely to start up. They turn the light off, start the compressor, and then turn the light back on. The light slows down the compressor a little bit, but since it's past its super-high-current starting phase, it keeps running.


Perhaps something more technically plausible is they buy a 500-foot roll (in your WIP it may take several rolls) of Romex (brand name of house wiring - stiff wire meant for permanent in-wall installations rather than "portable" use) - this roll will weigh maybe 100 pounds and at current copper prices probably cost well over $200 (so perhaps they steal it). They fix plugs and jacks on the ends and do their thing. This will work better than extension cords, but even that many extension cords will be expensive and heavy. Check your local hardware/home improvement store...

You would have to use 14 gauge Romex as mentioned above.

Normal or standard extension cords would not work at all. There would be too much voltage loss due to wire resistance.

Also bear in mind, most compressors need 20 Amp service. Most household outlet circuits are 15 Amp.

Prawn said:

In my WIP, I have a thick, industrial extension cord going off a third floor balcony, and down into a basement, then into a passage several hundred yards long.
Is their a limit to over how long a distance you can chain extension cords together?

Click to expand...

Yes there is a limit ... and you are over it.

http://www.machinetoolhelp.com/misc/toolsdata/extensioncordlengths.html

You'll burn something up at that length no doubt...

Air compressors draw a crapload of power. Usually an isolated circuit and heavy wiring. Mine has a twenty-five foot extension cord and that's about the limit I'd want to go. The plug still heats up slightly.

Usual approach if using a compressor a distance from the power source is to fill it, truck it to the job, use it, and then bring it back. Or rent a portable generator if it's a long job. A portable generator is probably going to cost you less than the extension cords you're going to need anyways (you're going to be using the biggest, heaviest extension cords you can find).

The other approach is going with Romex and wiring that way. But I'd pay for a professional to install it. And I do a lot of my own electrical work.

And I'd go with a 30 amp fuse for the sucker. Especially a compressor with some age on it takes so much juice to start the sucker.

Best of luck,

Jim Clark-Dawe

An extention cord that long wouldn't even power a small motor, like a saw. No way a compressor would run.

If it is an air compressor, there is another solution .. leave the compressor in the room and run the compressed air line all that distance.

Compressed air lines can go long distances without too many issues.

It also means that the noise of the compressor is a long way away, too!

Good luck,

Mac

Why not a gas powered generator?

From practical experience, I can tell you that you can chain together a few hundred feet of extension cord and run a small motor.

Have a couple acre property -- it's a few hundred feet to the back of the property, and there's no power back there. I've run extension cords out to the far corners of the property to run things like weed whackers and power tools. Not a big issue. Wouldn't recommend it from a safety aspect, but sometimes, you gotta do what you gotta do.

For small job (usually carpentry-associated stuff) I use a 12 volt battery and an inverter. You can run a drill or power saw for quite awhile (hours, of intemittent use) off a 12 volt car battery. And it's easier to carry a battery to the back of the lot than it is to drag a bunch of extension cords back there ... you'd be surprised at what you can run off a car battery.

I'd imagine the same would apply for a small air compresser. If it's got an air tank attached, it wouldn't be running all the time, just when the air got low.

They could use a gas powered compressor, then theres no need for electricity.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=5637

With the Honda motor and being underground it would not be heard very far. If they started the motor only when they need to recharge the tank it might work.

How deep underground is it? I'm no expert, but I'd say five feet-ish would effectively soundproof the tunnel. Also, out of curiosity, how are they disposing of the dirt, supporting the ceiling/walls, and all that? This sounds interesting.

if you're using a number of ext. cords, they should all be the same type. Also, a car battery probably wouldn't have the oomph needed. You'd need something bigger/stronger.