I will be running wire to my shop that is aprox 250' from the main elect box at the house. I would like to have 220 volts and 110 volts. The wire will be buried underground the average temp in my area in the summer is 100 degrees. What size wire should I use. I will be welding with a welder that draws around 30 amps. All the info you can give me as in wire size, breaker sizes. Thank you

jim taylor

Reference :
Wire Gauges
Let's just start with the normal situation :
.
30 Amps for welder.
How much for light and sockets?
How much for anything additional?
Let say that's all together 60 Amps. (make sure that is indeed so).
60 Amps means 4" wire.
.
Now let's see for changes for the remote situation :
.
The problem here is the distance of 250'= 80 yards.

See : Amps and Wire Gauge - 12V Circuit

Based on 60 Amps :

OFFICIONAL cable ratings :
AWG 4 up to 20 feet
AWG 2 up to 30 feet
AWG 1 up to 60 feet
AWG 3/0 up to 90 feet

250'= 75 meter. Cable resistance is 2 x distance= 150 meter (hot + neutral)

AWG 4 = 0.8 Ohm/1000 meter or 0.12 Ohm/150 meter or loss of 7,2 Volt
AWG 2 = 0.5 Ohm/1000 meter or 0.075 Ohm/150 meter or loss of 4,5 Volt
AWG 1 = 0,4 Ohm/1000 meter or 0.06 Ohm/150 meter or loss of 3.6 Volt
AWG 3/0 = 0.2 Ohm/1000 meter or 0.03 Ohm/150 meter or loss of 1.8 Volt

Suggested wire size = min. AWG 3/0 With voltage drop of less than 2 volts at 60 Amps.

The fuse depends on the real current and therefore remains 60 Amps.
Hope this helped you sufficiently.
If not contact me by clicking my handle and go to private mail.
:)

For a 60 amp load at 120/240 volts, use #4/0 aluminum wire. This will result with 2.2 % voltage drop. Much less cost than copper wire.

The max recommended by NEC for a feeder is 3 %.

If you want to use direct buried cable, look for URD (Underground Residential Distribution) cable. It has 4 conductors, twisted into one cable assembly,and uses USE insulation, rated for direct bury.

This cable is usually available at the home stores, and certainly at an electrical distributor. The wire size is too large for the connection terminals at both nds, so wire reducers or splices with smaller wire to match the terminal sizes will be needed.

If you want conduit, for this length of run , I would use 3 " PVC Sch 40, oversized to help with the wire pull, and 3 - #4/0 for the two hots and one neutral, and 1 - #2 Al for the equipment ground, all with XHHW insulation.

Are you guys serious?? 4/0 for a 60A sub panel?? How is anyone EVER supposed to terminate that cable. I want to know where in the world you came up with 4/0 for 60A at 250 feet??

Besides, you DO NOT use the full 60A when figuring voltage drop. You use the calculated load.

Also, the 3% number is way conservative. There is ABSOLUTELY NO reason to go under 3%. NONE.


Credendovidis, you need to be careful giving advice on US based boards. This last post of yours is SO far off it's not funny. That link you provided is for 12 volt systems. This is 120/240v!!


For the average 60A sub-panel #6 is typical and perfectly fine. Over 150' or so you should bump up to the next size. #4cu.

For an estimated 50A load, at 250', at 240v, using #4cu wire, the VD is 3.2% . COMPLETELY acceptable.
In fact 5% is acceptable by the letter of the SUGGESTED code.
The issue of voltage drop is NOT code required. It is merely suggested.

Stan, you may provide any advice you see fit, as I will.

If you feel I have provided an inacurrate answer then your free to use the "Report Inappropriate Post" button.

I stated 3% is recommended, I did not state "required".

Seems your using 240 volts to calculate the voltage drop at 3.2%.

I use 120 volts. Using your example, a 50 amp load will result in 6% Vd.

While the question revolves around a 240 volt tool, and it is possible but not probable to have a 50 amp 120 volt load, I use 120 volts to arrive at a reasonable worst case scenario that may occur.

What is calculated load? Running load of 50 amps? What about inrush current of the welder, and locked rotor amps of a motor starting? These, while not always apparent and seldom considered, will occur and will result in greater voltage drop at a time it is most needed to be at reduced level.

I also addressed the large wire in small terminal issue.

While 3% is conservative, this is a feeder already downstream of a utility feeder, panelboard, and who knows what, so better to be a bit conservative, still need to consider the length of any branch circuit, and this is where the remaining 2 % can be considered.

And I offered a readily commonly used aluminum cable as an alternative solution due to the high cost of copper. Plus over size will allow an easy increase in amperage load if and when the poster adds more load to his shop. Code does require that future expansion be considered.

No. I don't play that game unless the post is literally threatening.
I am not threatened by you TK.


Yes I am. We are talking about a 120/240v feeder. The notion that this feeder would be even close to 100% imbalanced is absurd.

NO. It would be 9.53% with #6. VD is NOT directly proportionate to voltage. It is compounded.
A 120v circuit will have over three times the VD than that of a 240v circuit with the same load.

I would safely say is it almost not possible. You will have some imbalance but you would have to intentionally lay out the breakers so that you would get any drastic load imbalance.



Yes, but 4/0?? Sure, you can suggest what you want and I'll suggest what I feel is correct.