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Advice needed for ultra long 50 or better 100 amp extension

Advice needed for ultra long 50 or better 100 amp extension

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  #1  
Old 10-25-16, 03:21 PM
J
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Advice needed for ultra long 50 or better 100 amp extension

Hi,

I need to operate a welder, plasma cutter and compressor about 300 feet away from the electric construction pole. If I run the calculators, 100 amp comes out at 2 AWG and 50 amps at 4 AWG.

No this is only for temporary use and its outside, so I do not care if the cable gets burning hot. I think none of the tools should be ultra sensitive to voltage drop. I am looking for the cheapest solution. It's single phase, so L1 L2 and ground should be enough. Ground should not need full diameter or ?

I have a cheap 6/6/10 cable offer, could that be used ? Any electrician here who can do a good recommendation?

Thanks
 
  #2  
Old 10-25-16, 04:31 PM
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Sounds like a good way to burn out the motor on the compressor. We need to know full load amps of each machine and duty cycle of the welder.

Best guess would be to run 2-2-2-4 quad-plex overhead to a subpanel at the location of the machines.
 
  #3  
Old 10-25-16, 06:46 PM
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Cheapest way? Rent a generator.

Ray is correct, the compressor motor will be the biggest issue. IT will draw 3x the current on startup and the voltage will sag a lot possible damaging the motor. The only two machines that will run at the same time is the compressor and plasma cutter (unless the welder is a TIG) We need the nameplate current of those two machines.

300' of 6/2 NM-b cable is going to cost a pretty penny. The home stores will only sell you a full roll. 500' of 6-2 NMb is $461 at Big Orange. By the foot is $1.79.
 
  #4  
Old 10-26-16, 02:07 PM
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Yeah I agree that renting a generator is certainly something you should look at. You should be able to get a tow-behind diesel generator for a week for about the same price, maybe even a little less, as that much cable.
 
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Old 10-27-16, 08:38 AM
J
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Thanks for the great replies.

Lets try to address the issues:

1.) Compressor and 3 x startup load

This could be solved by a huge capacitor. However, those are expensive of course too. Maybe I put the compressor closer to the outlet and use a long and big air cable. 100 feet 1/2 inch is less than 50 $. I know this is an electric thread, but anybody by chance has any knowledge if a 300 feet air hose would be an issue ?

2.) Welder and cutter

Both models are everlast and both have standard Nema 6-50 plugs. This is a little confusing because welder input says max 55 amp and cutter 70 amps ! How can that be on a nema 6/50 ? (models are MTS 400 and 80 S). Duty cycle on both is rated at 100 % at the amps I will pull, but I would assume will be rather in the 60 % range based on the work.

Looking into aluminium cables, I think the best option is to use this:

https://www.wireandcableyourway.com/...ing-wire.html?

It's rated at 160/215 amps and voltage sag for 300 feet would be 3.88 % @ 100 amps. if I move the compressor to a separate plug close to the outlet I think I should be fine ?

Last question. if the compressor pulls 3x on startup, does the fuse not pop ? I have two 50 amp and one 100 amp breaker outlet at the power pole.

Generator is no option as this consctrucion will go on for month.

Thanks again for all your great help
 
  #6  
Old 10-27-16, 10:15 AM
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"air cable"? That made me chuckle. Air hose can be run any length you want. What it will affect is the cfm. When no air is being used the air inside any length hose will be the same. When you use air at the end the resistance in the hose will slow the air and reduce the CFM at the end. Smaller and longer hoses have more resistance and have less CFM.

You haven't provided the rating or power requirement of your compressor so we can't comment whether or not your circuit breakers will trip. The breaker will either need to be oversized to handle the initial starting load or use a slow acting breaker that's intended for motors.
 
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Old 10-27-16, 02:37 PM
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It's usually better with the air compressor to use a longer hose and a shorter electrical cable if you can.

If it's an actual fuse on the compressor it should be a Slow-blow to allow for the start-up current. A standard fast acting fuse would blow when the compressor starts. Modern breakers have an HCAR rating that allows a large start-up surge for a couple seconds for motors.

That #1/0 aluminum URD cable you linked would be OK, but check in to aluminum service drop cable -- it might be a little cheaper than the URD (underground) cable. Make sure to secure and terminate it well at both ends. Use no-ox paste on the terminations to protect the exposed aluminum. You can support it by setting temporary poles or making a tee-pee out of three 12 foot 2x4s.
 
  #8  
Old 10-27-16, 06:10 PM
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It's usually better with the air compressor to use a longer hose and a shorter electrical cable if you can.
True, PROVIDED that you use a large enough air hose to supply the load. The concept is exactly the same as voltage drop with electricity, the longer the hose run the more power lost through the run.

Depending upon the pressure AND flow required at the point of use along with the sustained pressure output by the compressor AND the sustained flow rate I think I would use nothing less than a 3/4 inch inside diameter hose. If it will be an intermittent load, like a nail gun, then a smaller hose plus a surge tank of about five or ten gallon size near the point of use will be fine. If it is for a continuous-use tool like a sander/grinder, drill, impact wrench or even the plasma cutter used for extended periods you will need the larger hose. Most air tools require 90 psi continuous supply at the tool for best operation.
 
 

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