OT: Barn Electric

My original intent was to put 100 amp 117vac service out there. Now, a neighbor is suggesting I pump 220 out to it. Q: Will that cable support 220? I really don't need 220v now since my compressor, welder etc. are all 110. I guess it might be nice some day. What do you guys think?

There are two problems with this setup: First, as others have said, the #2 aluminum is way too light. Second, the "local ground rod in lieu of four conductors" is not up to code. You need four conductors PLUS two local ground rods.

OK, what can you do to salvage this situation? If your trench is still open, I'd bury another #2 aluminum USE so you have four conductors per code. If it's closed, then go with your current plan. Two ground rods (per code) are better than one, however.

Now with regards to your desire for 220V, you already have it. I assume you're putting a 100 amp panel in your barn. It has two hot sides, each is 120 to neutral, but you get a total of 240 from hot to hot. So if you plug a 240V breaker in your panel, you have 240V.

To make the most of your marginal setup, you need to minimize the current in the neutral conductor. You do this in two ways: 1) use 240V equipment as much as possible, and 2) balance the loads on the two phases. If you can convert your compressor to 240V, by all means do so. It will cut the total current in half, while eliminating the voltage drop in the neutral conductor. Put your lighting on the opposite phase as your 120V outlets to help balance the loads. on each phase.

Link

your 400 foot run of #2 triplex is only good for 28 amps at 220v. You might be able to push 30 amps.

For such a low amp rating, you for sure want to use both legs of the wire, so you have 2 110v circuts. Or one weak 220v one.

After all, you alrady have the 3 wires burried - why not use them????? ?

If you only used one hot wire for 110v, you would only have 15 amps out there. hardly worth bothering with.

According to that same vdc, if the run is only 50 feet long, that same #2 wire could handle a 200 amp draw. That surprises me.

Distance makes a big difference.

--->Paul

Some answers to some of the questions:
My electrician specced the #2. It is three conductors, plus I (he) will drive a ground rod at the barn.

Mahalo,
doogdoog

Best wishes

John T

You really should have 3, two hot and one neutral, if you are going to use 240 v and 120 v devices and I ran 4 so I could tie the ground back to the ground at the house.

Consider upgrades using 240 volt motors for like a small compressor or a 240 volt welder so they only draw ONE HALF as much current and theres less voltage drop in that long wire run.....

THAT BEING SAID, but depending on the current draw, and based upon a 400 foot wire run, that No. 2 aluminum you chose is smaller then I would have recommended so as to lessen voltage drop across the 400 feet of cable. Thats NOT to say it wont work, its just to say at high current draw the lines voltage drop could become a problematic issue on bigger motor loads.

REGARDLESS OF ANY VOLTAGE DROP CONCERNS, if you run both phases out there (A & B) for 240 volts but balance individual 120 volt loads the best you can (some loads on Phase A the others on Phase B) you will reduce the Neutral return current WHICH IS A DEFINITE POSITIVE. If theres the same pure resistive load (at same phase angle etc) on both phases of 120 volts, there wouldnt be any Neutral current YAYYYYY YYYY

YES that wire will handle 240 volts, it would have one leg like Phase A red on one conductor and the other Phase B black on the other with the common bare/white conductor serving as the Neutral return current path. SUBJECT TO DISCLAIMER BELOW CONCERNING 3 VERSUS 4 CONDUCTORS

Sooooo oooo Id definitely run 240 volts out there..... ..Id use 240 volt motors or welders wherever possible,,,,, ,,Voltage Drop could (depends on load amps) be a problem.

You can go to Dave Holts or other electrical websites to plug in the wire size and length in feet and the amperage to determine voltage drop if necessary, but if you already have that wire buried you can, of course, go ahead and use it for a 120/240 volt service (depending n subject to load amps and voltage drop) just rememebr 240 volt loads will only draw half the current and reduce voltage drop..... .....

DISCLAIMER Im too rusty on the NEC (long retired) n too lazy to look up the rules regarding services to remote agricultural buildings regarding any necessity for four versus only three conductors from your main service panel to that remote location (if you run 240 volts) PLUS around here with pole buildings having concrete floors we have to use GFI receptacles!!!!! ! BE ADVISED N FOREWARNED

John T (LOng retired electrical engineer)

http://www.mikeholt.com/index.php?id=homegeneral

• Mike Holt

You don't have 200 amp service, its limited by the wires to 50 amp service.

Gerald J.

--->Paul

The No 2 is more of a common size for a 100 amp,,,,, ,, NOT a 200 amp service.

Thats NOT to say it dont work fine provided youre NOT pulling any big loads buttttt ttttt if you try to continually draw 200 amps on those No 2 conductors youre gonna eventually experience a meltdown lol Sure its not just a 100 amp service????? ????? ? Its hard to believe any competent electrician would have only used 100 amp rated feeder conductors on a 200 amp service ????? ????

PS maybe you have a 200 amp panelboard but its just fuzed/circuit breaker protected at 100 amps !!!!! !!!!! cuz I just dont see how they would have tried to provide 200 amps of service
with only 100 amps worth of wire !!!!! !

John T Long retired EE

• Hobby farm