Wire gauge for a certain length and load?

[chenopod]

I have a few questions that involve simple electrical wire theory, but the situation gets a little bit complicated.

I am trying to run an extension cord (or cords) into the woods to power a stage, with fairly powerful musical equipment, lights, PA, etc.

I'm assuming the power outlets that will be available are standard grounded 120 Volt, hopefully on the heavy duty side. The equipment I'm looking to power totals several thousand watts (rated at, lets say, 3000 W). However, the power draw is not consistent... it fluctuates with how hard the equipment is being pushed from moment to moment.

The distance is more than 1000 feet (probably more like 2000 ft). If I were to buy a single cord that is suitable for this job, I'm guessing the outlet itself would be the limiting factor in terms of resistance and heat, and I don't want to start any fires. I'm not even sure if a wire that is a large enough gauge would even come with the standard outlet plug. At this power draw and distance, even several 120-V outlets might not do the job, if the wire that runs from the power lines to the outlet box (or any internal wiring) is not a heavy enough gauge. For this type of job, do I need to look into other methods of getting enough power from the pole besides running several extension cords?

Does anyone have any specific advice on how to tackle this problem? (i.e. what type of gauge wire, how many extension cords, how to correctly tap the power lines, etc.)

Your help is most appreciated.

-Dave

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[John Grabowski]

Is there any reason why you cannot rent or buy a generator? A two thousand foot extension cord is not very practical for such a small load. You can get heavier gauge SO cord or single conductors but the wire will be quite expensive and heavy and you will need connectors every few hundred feet.

If you are concerned about noise from a generator, contact companies that rent motion picture equipment. Their generators are practically noiseless.

[Oren]

Rent-A-Generator

[Ralph Mowery]

You should look at another way to supply the power. It would take 2 or 3 extension cords made out of # 6 or # 8 copper wire. This is not something off the local electrical store. You would have to find seperate circuits to plug into. Most home 120v outlets are only good for 15 or 20 amps. It would take about 10 amps per 1200 watts.

A big part of the problem is the voltage drop of the wires. Too small wire and there will not be enough voltage to power the load.

[Erma1ina]

Eighty 25 ft, 20 gauge TROLL-e-lectric extension cords in series should do. Just plug the set into any 5 amp outlet and you're good to go. ;-)

[ransley]

TROLL A Generator, its a bunch of trolls cranking a gen unit. You could buy many many generators cheaper than the cable yur troliin fer

[hallerb]

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a friend does shows and has similiar issues. all solved by using a inverter connected to her vans battery, with the engine running.

one must realize that loads like audio systems rated a X watts, is audio watts out. much less than power line voltage watts in.

my friends entire audio system and some lamps run fine on a 1000 watt inverter. plus its a variable load, the inverter doesnt even get warm.

put a meter, like a clamp on amp meter or kill a watt meter on the entire setup. you will likely be pleasantly surprised........

[ransley]

d)

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Audio watts out can easily and more than equal input, my 600w rms mono power amp will blow a 15amp fuse on peaks, and its no cheapie at

1000$, I have another 200w head that uses a 3.5 amp fuse. A music group will likely need all that 3000 plus 2000+ in intermitant peaks.

[S. Barker]

Get a rental generator of the proper size and put it behind the stage. You'll never hear it. Save a lot of trouble and cording and such.

s

[HeyBub]

Is it really appropriate to use modern, electronic equipment for a back-to-nature event?

Wouldn't strolling minstrels be better?

[hallerb]

pod)

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assemble the entire system, and monitor its power use.........

only way to know for certain/

[Chris Hill]

3kw is at least 30a of 120v current. You could plug it all into two outlets on two circuit breakers, if you weren't 3000 feet away. Since you are, there would be a great deal of loss in the lines going back, and you'd have to run two cords. Your best bet is to rent one large quiet generator; get 4-5kw so you aren't pushing it too hard. If you want to buy something, buy a pair of Honda EU 2000 units with the parallel wiring kit. They are very quiet and will likely last forever in the use you propose. This would probably be only about double the price you'd pay for the wiring to do the job with extension cords, and it would actually work.

[hallerb]

a wire

if its a one shot deal, the best bet is a generator.

if its a long term use location direct burial cable, or even get a quote from the local power company for some poles and a transformer at the site.

such a estimate should be free.

if you can get a vehicle to the location, and thats likely given the equiptement used.

a generator powered from a vehicle, or a inverter on a vehicle, or two inverters on 2 seperate vehicles might be cost effective.

inverters are nice to have around

[Chris Hill]

That's the best idea for a long-term venue. Runing cables without a transformer would require very heavy cables and the cost would be quite high. By the time you bought and buried the cables for a 110 or

220 volt solution, you could have paid for the generators and you wouldn't have a trench to fill in.

[HeyBub]

One walk-in-off-the-street price for 6-3 outdoor wire comes to about $3.50 / ft. Say 1500 feet, you're talking over $5000.

Buy a trailer-mounted propane powered diesel generator.

[nicksanspam]

How much for a couple of used 3 kVA 240-480V transformers and skinnier wire?

Nick

[HeyBub]

Dunno. Say half price ($2500). A propane-powered generator is less than $1000.

e.g.:

[David Nebenzahl]

On 5/11/2008 4:51 AM [e-mail] spake thus:

Interesting idea (and I see someone gave some ballpark figures down yonder).

I'm wondering about losses: how much power would be lost in that pair of xformers?

In case anyone's wondering why in the world one would want to do this, it's because the higher the voltage, the skinnier the wire needed to carry the same (power) load (think high-voltage transmission lines), with smaller losses due to resistance.

[hallerb]

transformers are pretty efficent, otherwise power companies wouldnt use them. I will ask a buddy of mine who used to work for allis chalmers in the 60s, he was a design engineer for power company transformers. given their long life many he designed are likely still in use today.

[Ralph Mowery]

Most transformers do not have very much power loss. They can be around 98% efficent for well designed ones to 80 % for small not so well designed ones.