Author Topic: Distance between generator and point of use  (Read 7074 times)

veggie

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Distance between generator and point of use
« on: September 04, 2014, 04:30:43 AM »
Anyone here have a generator located 250 ft. or more from the house (or the point of power use)?
One possible site for me is a Barn which is approx 250 ft from the dwelling.
I would like to know if there are any issues in locating my Lister SR2 - 5kw generator in the barn and running a L--o--n--g power line to the transfer switch plug at the dwelling.
The line would be a combination of above ground (along a fence) and trenched from the fence to the dwelling.

anyone else with a run this long ?

veggie
« Last Edit: September 04, 2014, 05:02:11 AM by veggie »
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dieselgman

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Re: Distance between generator and point of use
« Reply #1 on: September 04, 2014, 04:52:29 AM »
I have used over 1,500' of power leads from generator to point of use before. Voltage drop is the big issue and is directly related to amount of current you need to draw and your cabling ampacity. The losses in very long runs are high unless you can afford very heavy cabling. There are some loads that are not very affected by lower voltages and many that are inoperable with that problem. lighting and lightly loaded circuits - generally no big problem.

Several things to look at, how heavy a cable can you afford? Look up the ampacity charts in the NEC (electrical codes) this will indicate amount of loading (in amps) that can be tolerated with a given length and gauge of cable.

Look at your necessary loads and decide based on the charts if your loads are compatible with the cabling you have available - or simply size your cable to match the load if you have the budget.

It is possible to use step-up and down transformers in this situation but they also incur additional losses and should not be necessary in your case. 250' is not an excessively long run for less than 5kW of loads.

I would also suggest to you that heavy overhead aluminum distribution line can be cheaper than along the ground copper in most locales. Your power company might even have surplus or cut-offs at a deep discount.

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« Last Edit: September 04, 2014, 05:02:07 AM by dieselgman »
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millman56

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Re: Distance between generator and point of use
« Reply #2 on: September 04, 2014, 08:17:32 AM »
Part of my set up has a run of at least 200`using 2.5 sq mm cabling, its 230 Volt, I can easily check the voltage drop over this with a 2KW load and give you some practical results.

Mark.

BruceM

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Re: Distance between generator and point of use
« Reply #3 on: September 04, 2014, 03:26:52 PM »
For the relatively short distance you're talking,  aluminum wire, as dieselgman suggests, is probably the best route.  Direct burial aluminum is most often used here.  Wire size vs distance for an acceptable voltage drop (2%) for aluminum or copper wire is easily found on the web.

My generator building  is sited over a hill from my house, and thus about 400 feet from my shop.  As long as you follow the wire size charts for your distance, distance is not a problem.  I distributed 240VAC only (just 2 wires) and then stepped it down to 120V via toroidal transformer, avoiding ST-3 load balance issues and saving on wire size. For very long runs, you can step up/down the voltage to reduce wire size even further, as wire size is determined by amperage.

Here's a link to a wire size calculator:

http://www.calculator.net/voltage-drop-calculator.html
« Last Edit: September 04, 2014, 09:13:47 PM by BruceM »

Tom

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Re: Distance between generator and point of use
« Reply #4 on: September 04, 2014, 06:02:12 PM »
The power shed at our old homestead was right at 250' from the house. My calculations showed that 4ga copper would handle the load for a 6kw generator. I found a deal on a 1000' roll of 3ga copper and put it into conduit. We have LOTS of gophers around here so I feel better about using a conduit rather than direct burial wire. While the trench was open a LP pipe was added too so the tank was a good ways from the house. The same tank also ran the generator.
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Horsepoor

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Re: Distance between generator and point of use
« Reply #5 on: September 04, 2014, 06:08:43 PM »
My run is 300 feet from the generator shed to the transfer switch, then into the house and the distribution panel. I was concerned about voltage drop at maximum power usage (50A - 240VAC). I used AWG #1 gage for the conductors and less for the neutral and ground (IIRC AWG #4). I do not regret spending the extra money.

Part of the #1 AWG justification was the permitting process for the tool shed with 100 amp service. I ran a line 50 feet from the genereator shed to hit the 250 foot line running from the tool shed to the house service panel. Thus, 250 + 50 = 300 feet run.

My suggestion is spend as much as you can on wire, over build if you can, do it right, and you'll never have to worry about voltage drops, poor performance, insulation fire, etc.
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millman56

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Re: Distance between generator and point of use
« Reply #6 on: September 04, 2014, 09:03:43 PM »
Directly connected to the generator  5.5 amps @ 220 Volts. Down approx  200`  of 2.5 sq mm cable 5.3 amps@  209 Volts, exactly the same load and frequency.  These measurements were taken with a combined Hz, Volts and Amp meter.

Mark.

mike90045

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Re: Distance between generator and point of use
« Reply #7 on: September 04, 2014, 09:08:00 PM »
I'm about 200' from my power source (XW6048 inverter & listeroid on autotransfer switch) and I'm running 200' of #2 aluminum wire.   No problems.    Just don't try to run your toaster oven on a 100', 16 ga extension cord.

buickanddeere

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Re: Distance between generator and point of use
« Reply #8 on: September 05, 2014, 01:41:56 AM »
  Your system will tend to suffer VD, in particular when starting motors.
  As previously stated. Save yourself a world of trouble and bury the cable in a conduit instead of direct burial.
  You can run a pair of #14 wire back to the generator from the building distribution/breaker panel back to the voltage sensing input of the generator's voltage regulator.  The voltage regulator will boost excitation to compensate for VD. Wide voltage swings will be eliminated.
  At that and longer distances. I would look at kijiji etc and find a pair of 10KW single phase 120/240 to 600 transformers. Step up at the generator and step down at the panel.