Welder / electric / barn question

[Scott in IN]

My house is 600 feet from the road and though the electric company only guarantees voltage 300 feet from the road, all is good. The problem is that I want to run power to my barn which is around another 400 feet further from the road, which I"m thinking would be a problem (voltage drop and such).

I"m wanting to run a stick welder (50 amp / 220 buzzbox), air compressor (110 volts) and at some point a mill and a lathe (via a phase converter) along with lights and power tools (not all at the same time). The barn is already wired for lights and 110 plugs for my 6.5K watt generator (but it barely runs my compressor). Soooooo I can either:

1. Spend + or - $7,000 (which I don"t have) to put in a new 7.8KV feed 600 feet long up to the house and then run it into a step down transformer and then run it into the house and then barn.

2. Buy a ($2K) bigger generator (I"m thinking 15K watts would do) and run the barn with the generator when I need to weld or use machine tools (just on weekends and such). Maybe a diesel or water cooled unit..

3. Buy one of those ($3K) slick Miller or Lincoln combo welder/generator units. Use the welder part to weld and the 10.0k watt generator to run the rest of the barn.

Number 2 looks the most appealing for cost but thoughts from the group?

Scott

 

[rustyj]

Probably be cheaper to move the barn closer to yer house, wouldn't it?

 

[Anonymous-0]

A lot depends on planned use, intermittant or forty hours a week.
Also see windmill thread on tractor talk.

 

[Scott in IN]

Just every so often, when something breaks or putzing around..

 

[scott#2]

In welding, proper voltages and current rule when it comes to good beads. I would probably start looking for a Miller big 40 diesel or better. Some can be had for 2-3 k and are capable of multi process welding, mig, stick, tig, etc. You could even run a plasma cutter off of it and it would handle all your lighting needs. Might want to make it reasonably portable, they fill in for house current pretty well when the lights go out. Pretty quiet and fuel effecient. Forget about runing a phase converter on a generator, you need about 2 horse of phase coonverter for every horse of motor load for any machine. Change the motors to 110/220 single phase on your machines. Youll probably never use more than 10 kw, motor start load is the critical factor here, know the surge rating of what ever genset you buy. I can run a whole house, all lights, 3 refrigerators, ac, furnace/pump, multiple ups's, fans, 2 tvs, stove and oven (minus 1 burner) on 12.5. Turn on the other burner and it goes into overload and kicks out.

scott#2

 

[paul]

Trench in the wire.

If you plan to stay there a lifetime, the rest of your life you can walk the 400 feet to your shed, flip on a switch & weld, or mill, or....

Any other option, you end up putzing, fixing, sloshing fuel, ...... Actually getting anything done is a lot less fun under those condtions, and you find yourself staying in the house.....

--->Paul

 

[kurt:ky]

If it only weekends and not daily and probably not every weekend I would look into a welder generator combo. My gas air commpressor and Miller welder cv and cc unit mounted in my truck does me well. It sticks- migs -and tigs. For mig and flux-core,I use a Miller VS 12 Extreme wire feeder.

 

[Anonymous-0]

In comparing your financial cases, you need to add the operating costs to your capital outlay. Compare option 1 & 2, you have a $5,000 capital savings minus the operating expenses.
Assumptions
1. Cost of Electricity: $.10/kw hr
2. Use your barn for 12 hours/weekend
3. Use 110 kw hrs/weekend
4. Diesel fuel - $3/gallon
5. Generator uses 1 gallon/hr
6. X = number of weeks to break even

$5,000 = X*$3/gal*12 hrs/weekend-X*$0.10*110kw
X = $5,000/25
X = 200 weekends or 4 years to break even

You need to estimate your electrical usage/weekend to get a better comparison. 110 kw hrs/weekend is quite high. If it was 50kw hrs/weekend, your break even point would be 161 weekends or 3 years.

Good Luck

 

[suptscottyb]

400 ft is not that far. I ran 300 ft to a new 100amp sub panel for the wells 2 years ago at about 1.50 ft. Even if costs have doubled, I would run copper out to the barn.

 

[Anonymous-0]

A portable welder would most likely be DC current and would be superior to a buzz box with the added benefit of being able to take wherever it is needed. Like if something broke in the field. Dave

 

[scott#2]

JIC

http://www.powerstream.com/Wire_Size.htm

 

[Greg_Ky]

I ran 600ft. of 2" pvc conduit underground with steel 90 degree sweeps at each end and installed a transformer pad from the power company and it only cost me $585.00 for the cost of the wire when the power company pulled it in and set the transformer. (the year 2001)

 

[Greg_Ky]

Should have also said the conduit if I remember correctly was around $400.00

 

[MarkB_MI]

You don't say what kind of service you have to your house. If you have 200 amp service, then I don't see why you couldn't run 2/0 or heavier cable out to your shop for 100 amp service.

Now if you have less than 100 amp service to your house, then you really should upgrade to 200 amp service anyway, and even 100 amp is marginal these days. Of course, if you want to upgrade, the power company will probably insist on moving the transformer up to your house.

I'm wondering how you ended up with a transformer 600 feet from your house. It seems to me that at some point in time the power company screwed up; that should give you some leverage to get them to pay some or all of the cost of new service.

 

[Anonymous-0]

I'd go this route, trailer mount it and weld for the neighbors @ $50/hr.
3. Buy one of those ($3K) slick Miller or Lincoln combo welder/generator units. Use the welder part to weld and the 10.0k watt generator to run the rest of the barn.

 

[Stan in Oly, WA]

Hi farmall300u,

Nicely done! Perhaps it's not intuitive from looking at your equation or its results (it wasn't intuitive to me, and I'm generally quite good at this type of problem) that if the barn if used fewer hours per week and other factors remain constant, then the break even point will take more weeks. For example, 4 hours per week at the lower rate of electricity useage would extend the break even to a little over 9 years.

An interesting issue that can't be worked out by any math that I'm capable of is that the choice will change the variables, as Paul suggested in his posting. The inconvenience of everything involved in running a generator will inevitably reduce the amount that the shop is used; the less the shop is used, the more the generator seems the better choice. Conversely, the convenience of being able to use the shop by merely flipping a switch will increase the amount it is used, making electricity, relatively, the better choice. In other words, either choice will (tend to) create a situation which will support it as the better choice.

All the best, Stan

 

[Dan Woodall]

You won't have any problems running that equipment on less than 100 amp service, I have the same setup in an old barn running (2) Lathes, (1) Mill (2) welders (1 mig and 1 tig),a 220 AC unit, lights and ther hand tools with almost all that running at the same time, and I have yet to trip a breaker. I recommend burying the wire and do it right. It's too much work, and too loud to run a generator, plus it cost more in fuel. Dan.

 

[Bus Driver]

At that distance the voltage drop will be significant if several loads are online at the same time. With no current draw, there is no voltage drop. The higher the current draw, the greater the voltage drop. Better have an engineer look over your plan. Some electricians could do the proper calculations, but some who say they can, cannot. Mention was made of well pumps. Well pumps typically have motors with Service Factor (SF) of 1.5, occasionally higher. In simple terms, those motors will work well at significant voltage drops. A motor with SF of 1.0 or 1.05 will overheat with voltages more than about 5% low.

 

[Dick L]

How Do I Calculate Voltage Drop?
Sunday, January 1st, 2006
Q: I have a barn on my property that I would like to get power to. This barn is 377 feet from the nearest power. I would like to have 50 amps @240 volts and I’m going to run my power in conduit. What size wire do I need to run?

A: The formula for voltage drop is: Vd = 2K x L x I / Cm

Vd = Voltage Drop
I = Current in Conductor (Amperes)
L = One way Length of Circuit
Cm = Cross Section Area of Conductor (Circular Mils)
K = Resistance in ohms of one circular mil foot of conductor
K = 12.9 for Copper Conductors @ 75 degrees C
K = 21.2 for Aluminum Conductors @ 75 degree C
/ = Divided by

I will assume you are going to use copper conductors and your temperature is @ 75 degrees C.

Reasonable operating efficiency is achieved if the voltage drop of a feeder or a branch circuit is limited to 3 percent. However, the total voltage drop of a branch circuit plus a feeder can reach 5% and still achieve reasonable operating efficieny (210.19(A)(1)FPN No. 4 or 215.2(A)(4)FPN No. 2).

8 AWG = 50 amps @ 75 degrees C = 16510 Cm
Vd = 2 x 12.9 x 377 x 50 / 16510 = 30 volts
30 volts / 240 volts = 0.125 = 12.5% = Not Acceptable

6 AWG = 65 amps @ 75 degrees C = 26240 Cm
Vd = 2 x 12.9 x 377 x 50 / 26240 = 19 volts
19 volts / 240 volts = 0.079 = 7.9% = Not Acceptable

4 AWG = 85 amps @ 75 degrees C = 41740 Cm
Vd = 2 x 12.9 x 377 x 50 / 41740 = 12 volts
12 volts / 240 volts = 0.05 = 5% = Not Acceptable - This is not acceptable because the 5% voltage drop is at your sub panel. If you were to run any wire beyond the sub panel, your voltage drop would exceed 5%. I’m assuming you are going to install a light and some receptacles in your barn.

3 AWG = 100 amps @ 75 degrees C = 52620 Cm
Vd = 2 x 12.9 x 377 x 50 / 52620 = 9 volts
9 volts / 240 volts = 0.038 = 3.8% = Acceptable

Your equipment grounding conductor (ground wire) is sized off of table 250.122. You need to run a 10 AWG copper ground wire for this circuit.

To summarize; you need to run 3 - 3 AWG (2-hots and 1-neutral) branch circuit conductors and 1 - 10 AWG equipment grounding conductor (ground wire).

Check back tomorrow and I will show you how to calculate the conduit size for these conductors.

Tip:

Plan for voltage drop at 100 feet and increase one wire size for every 100 feet thereafter.

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