I have a friend who teaches guitar lessons. A while back he built a small building and had it wired with a #4 USE aluminum feeder. After about a year he's decided to move the building another 220 ft. From where it was, making the total distance around 380 ft. from the breaker to the subpanel in his building. Total load 30 amps.???
Ran out of room on my phone

Should be under 3% at the subpanel.

A quick Vd calculator is here...

http://www.southwire.com/support/voltage-drop-calculator.htm

You can put this calc in most smartphones.

Give it a try.

Question...how did he move the building??

Don't know how he moved it. It wasn't a large building. Probably a 12x12 or something like that. I'm on my computer now. I tried to type the question above in on my phone and it didn't give me enough room to finish. There is a 60 amp breaker ahead of this feeder. Like I said the actual load is 30 amps or less. The biggest load he will have is a window air condition ( 20 amp. ) and I'm assuming it is a 120 volt a/c. I figure without even without any demand factors the #4 USE should be a large enough wire to carry the load, even at that length. Just double checking myself on the figures. He wants me to splice the wire for him underground.
I figure if the load was even 4000 watts./240 = 16.6 amps, the wire is big enough, if I am figuring it right, and according to what he told me he had in the building, the total don't even come up to that if he runs everything at one time, which he won't.
Thanks again

Well I suppose in theory you still have to consider the breaker rating rather than the actual estimated load.

sparkync

Did you try the calculator in the link I posted above?

Using that calc app

the Vd would be 2.79% with a 30 amp load.

6.696 volts, so 233volts approx. at load, IF the source voltage is 240 volts.

Should be no problem.

I doubt that AC is anywhere close to 20 amps. The start up may spike up to a big number but running, these things are not that big a load. A 144 sq/ft building should be fine with half a ton. A 6k BTU window shaker pulls about 5a.
The playhouse we set up for the kids has a big old CRT TV in it, lights and a 1/2 ton AC. It runs fine on a 15a circuit.
I think the TV draws as much as the AC.

And now, for a different perspective ....

I think we are setting ourselves up for confusion when we focus on extraneous things like the "percentage" of voltage drop, or the running amps of the appliance.

Instead ... what's your EXACT voltage at the end of the line, when the circuit is under load? I'm looking at one air conditioner right now, whose nameplate is marked "115." There's my target; I need to deliver 115 volts to the air conditioner while it is running.

If your voltage at the house is, for example, 118.2 volts, you can afford to lose about three amps.; yet, there's a joker in the deck.

The 'joker' helps you, in that the manufacturer has designed the air conditioner to tolerate slightly lower voltages; you have a 10% margin from the nameplate marking. That is, you "can" use a supply voltage as low as 106 volts.
It's best not to use this "extra" margin, as you have to allow for drops in what the power company supplies you. That will depend partly on how many of your neighbors are running their air conditioners at the time.

Now, let's look at the issue of amperage. The same unit I looked at before says it needs a 15 amp circuit and draws 4.9 amps.

Why the difference? Because the motor needs more than 4.9 amps to start up; the '4.9' figure is just to keep it running. I need my wires to be big enough to deliver 15 amps, or the air conditioner won't start.

OK, so you have a 60-amp breaker feeding the smallest possible wires to the shed. That means there's no way you can supply the shed with 60 amps of power. Your panel should have a smaller 'main' breaker, perhaps a 40-amp, or you'll be setting yourself up for lower voltages when the panel is fully loaded. Lower voltages burn out motors and give electronics nervous breakdowns.

With the panel IN the shed, you can power the air conditioner in my example with an ordinary 15-amp circuit.

You're not really allowed to simply run a 15-amp circuit from the house, for the air conditioner in my example. Since there WILL be voltage drop, especially at start-up, you'll need at least a 20-amp circuit .... and you really ought to have that on a 15-amp breaker at the shed.

Bigger wire means less voltage drop. Higher supply voltages allow for a greater drop.

Your wire is plenty large enough, for even a 30-amp panel at the shed. This would allow you to power the air conditioner, and have a lighting circuit as well as two receptacle circuits.

As for your splice ....

Yes, there are those 'direct burial' wire nuts. I'm paranoid, though, and assume a splice is a weak point that will later need to be checked. I don't like buried splices.

Here's what I do:

I place a fiberglass 'handhole' in the ground. About the size of a 5-gallon pail, these have a top you can readily remove. The bottom remains wide open; I usually set a small amount of gravel there, just so I can 'fine tune' the way the box sits in the hole. I set the box to match the slope and level of the ground around it.

I leave enough loose wire to come out of the ground about a foot; this makes it much easier to work with. I connect the wires with ordinary wire nuts, then dip the connections in Scotch-Kote to waterproof them. Then, I fold the wires into the handhole, placing the nuts so they open downwards.

Reno:
The 60 amp cb in the source panel is protecting the feeder conductors, and possibly the buss in the subpanel.

And knowing the exact voltage available at the source panel will weigh on the exact voltage at the subpanel. Hence that is why my comments say "IF".

The common trade practice of using a percentage for Vd is how I was taught, and what is 'suggested' within the NEC as a FPN.

And, yes there are voltage tolerances that appliances and a lot of other equipment have.

In most European countries the rule is rather simple. You're allowed a total of 4.5% voltage drop from the service fuses but not more than 1.5% at the meter, that leaves you with 3% to the very end of the longest circuit. Your grid operator is responsible for supplying a voltage that keeps your appliances within limits if you stick to the 3% rule. VOltage drop is always calculated at full nominal circuit load, i.e. the size of the supplying fuse/breaker. The only exception to this rule are circuits that only supply one hard-wired load, usually a motor, which requires a larger fuse/breaker to account for startup inrush and the motor is protected by a thermal cutout.

The reason I stress actual voltage measurements is because you simply need to.

I'll use my own house as an example. It was pretty common to get measurements of 118 volts - well within the ratings of normal equipment. From NEMA standards, a nameplate rating of "120" would mean the appliance could be expected to operate properly anywhere between 132 and 108 volts.

For a simple CFL light bulb (maybe 13 watts), no voltage drop would be seen. There was nothing wrong with THAT circuit. Yet, the lights often dimmed.

By golly, when the water heater came on, the voltage dropped to as low as 92 volts - low enough to make the microwave oven simply not heat, motors to experience very short lives, etc.

There was nothing wrong with the water heater, or the house wiring. The problem proved to be damaged power company wires serving the neighborhood.

A similar issue arose when a restaurant had its' new exhaust fan burn out after a few months. When a new starter was installed, one with electronic overloads, the overloads kept tripping.

The cause of that intermittent low voltage problem proved to be overloaded ("saturated") transformers. Over the years, increased air conditioning and refrigeration loads at a neighboring grocery store, combined with summer heat and the lunchtime 'rush' at the restaurant created a demand the transformers simply could not provide.

You won't know these things unless you check the supply voltage regularly. That 3% calculation is a nice reference, but really tells you very little.

In residential settings, it's common for one home to receive considerably fewer volts than another, simply because one house is closer to the transformer than the other. The guy getting the 125 volts feed can afford to lose a lot more than the guy at the end of the street, who might be receiving only 110 volts - especially if every house before his has the air conditioner running!

Both homeowners need to start worrying at 108 volts- which means the last guy in line might be in trouble from the start. That's why the voltage needs to be checked under operating conditions .... the supply won't be under much stress when its' installed, if it's installed on an April morning.

I have had a Weston 901 meter plugged in here for a quarter century. my line voltage is pretty stable at 123-124 so I can afford a little voltage drop if I need to. That makes me feel better if I have 50' or 100' of extension cord strung out but that is actually rare because I have power wired everywhere.
I have one of those 1/2 ton A/Cs in the kids play house (a manufactured shed) and the voltage is still good there (120 or so) with it running. That is at the end of a pretty long 12ga branch circuit (100' or so) and then a 14ga extension cord going to the play house.

Things are getting interesting when someone's out in the sticks, say almost 1 km from the transformer (not all that unusual in Europe) and then needs power somewhere outside - achieved by plugging in two 50-m extension leads, 1.5 mm2. That's perfectly legal because in Austria and Germany voltage drop and short circuit current calculations only apply to fixed wiring but I doubt a short at the end of those 100 m (around 330 ft.) would do anything to a 16 A breaker but eventually trip the thermal overload. Since there are no mandatory maximum trip times for short/overload many even consider it relatively harmless to exceed the maximum VD in fixed wiring.

We ran the numbers on this a long time ago and I think it takes about a half a KM of 16 ga wire (typical cheap extension cord here) to dissipate 1800w without tripping a 15a breaker, assuming a bolted fault on the far end. Of course that assumes all of the receptacles and plug caps connect perfectly. It takes about 8 ohms end to end. so 250 meters would do it.

I seem to remember a few 'hot' cheap extension cords.

I remember the numbers you refer to Greg. I did a class project back when I was an instructor at Vo Tech on voltage drop. It kept the guys thinking for two (2) nights.

That's assuming a decent loop impedance at the meter though. I've heard of supplies where instant tripping a 16 A breaker (B type, i.e. instantaneous trip at 3-5 times nominal current) was already problematic. So assuming a lot of power is already dissipated before the meter you could get there. Keep in mind that it's much more common to have larger transformers with extended LV distribution even in rural areas in Europe! 1 km of LV from the transformer isn't at all unusual, supplying some ten houses.