[Midgetjoe]

Hey all,
Im pretty new to electrical, i know enough not to kill myself but not enough to necessarily do anything right. Will probably hire an electrician to do anything complicated, but i can wore panels and circuits no problem.

I have a couple very long runs I need to do. One to a shed down my driveway (about 350') that will have a security camera, a few lights (3-4), and a couple outlets for the occasional need (if i need to plug a drill etc in.) All of which are spread out over up to maybe an additional 100' past the shed. Maybe 10 amps max.

The second run is downhill into my field for about 420' where im building a play structure for paintball. Same thing....lights, maybe speakers, couple outlets. Then going another 360' at a right angle and doing the same thing again. 10 amps probably again.

I thought i had this figured out from digging around online and so bought 7500' of 8 Gauge copper wire (different colors, individual wires that i planned on running in conduit). Now im not so sure with the voltage drop.

If i wire a 40 amp subpanel (240v, 4 wires) at the shed and the first structure, then run circuits from there (and to the next structure on the downhill run) will that be too much voltage drop to run anything on the 8 gauge wire? Some people mentioned transformers (that i would definitely let an experienced person install) at the beginning and before the subpanels, is there specific ones that would work well? Some other people mentioned solar, im in texas so plenty of sunlight but idk the equipment I'd need to get from a solar panel to a outlet plug? (never worked with solar)

Basically how do i wire this with the 8 Gauge wire i already purchased if possible. Or cheaper than returning it and upgrading to super expensive huge wire. Is there a way?

Thanks.

 

[TarheelTerp]

One to a shed down my driveway (about 350') ...
The second ...for about 420' where im building a play structure for paintball.
(third) Then going another 360' at a right angle and doing the same thing

Now im not so sure with the voltage drop.
Basically how do i wire this with the 8 Gauge wire i already purchased

Basically... you can't expect to other than for branch circuits

 

[AllanJ]

Transformers are not that difficult to understand. You connect 120 volts to the input terminals and like magic 240 volts appear at the output terminals if that was the kind of transformer you wanted. So you have to pay attention to whether the transformer is sold/advertised for stepping up the voltage as opposed to stepping down voltage.

Just be sure to stay within the voltage and wattage ratings. Although you can connect a transformer backwards to convert voltage the other way (down or up) the wattage rating might be different when you do that.

Do the math to figure out the voltage drop all the way from the house main panel to the receptacle out in the field where things will be plugged in. This will give a better idea of how much power you will get with the #8 wire. You may well have enough for LED lights although for the drill it is questionable until the numbers are crunched.

Allowable voltage drop is 3 percent (some folks will insist you can get away with 4 percent) for the entire run.

You are not allowed 3% from the house wall where the line exits for the shed and another 3% from the shed to the playhouse and yet another 3% at right angles out to the third location.

Caution: Voltage drop is based on a round trip. Some voltage drop calculators assume a round trip when you plug in the distance, others do not, so the answers (calculated results) can be confusing.

You might save some distance by running a separate circuit directly from the house to the third location instead of branching off from the play house at right angles to go there.

Also note: The number of volts lost in the wires due to voltage drop depends on the amperes drawn at that moment but not on the circuit voltage. So if you lost (example only) 4 volts in the wires which is sligtly more than 3% at 120 volts, you would lose the same 4 volts or slightly more than 1-1/2% at 240 volts. You could put down twice the amperes at 240 volts and suffer the slightly over 3%. Stepping back down to 120 volts with another transformer, the total available amperage is double what went down at 240 volts for a net four times the usable amperage at the far end when you doubled the voltage for the majority of the long wire run compared with no transformers.

 

[AllanJ]

deleted ....................

 

[AllanJ]

Transformers are not that difficult to understand. You connect 120 volts to the input terminals and like magic 240 volts appear at the output terminals if that was the kind of transformer you wanted.

Just be sure to stay within the voltage and wattage ratings. Although you can connect a transformer backwards to convert voltage the other way (down or up) the wattage rating might be different when you do that. So you have to pay attention to whether the transformer is sold/advertised for stepping up the voltage as opposed to stepping down voltage.

Above are the first two paragraphs of my previous reply republished with corrections now rather than my waiting for the administrator to make changes after 30 minutes of editing time have expired.

 

[Midgetjoe]

Transformers are not that difficult to understand. You connect 120 volts to the input terminals and like magic 240 volts appear at the output terminals if that was the kind of transformer you wanted. So you have to pay attention to whether the transformer is sold/advertised for stepping up the voltage as opposed to stepping down voltage.

Just be sure to stay within the voltage and wattage ratings. Although you can connect a transformer backwards to convert voltage the other way (down or up) the wattage rating might be different when you do that.

Do the math to figure out the voltage drop all the way from the house main panel to the receptacle out in the field where things will be plugged in. This will give a better idea of how much power you will get with the #8 wire. You may well have enough for LED lights although for the drill it is questionable until the numbers are crunched.

Allowable voltage drop is 3 percent (some folks will insist you can get away with 4 percent) for the entire run.

You are not allowed 3% from the house wall where the line exits for the shed and another 3% from the shed to the playhouse and yet another 3% at right angles out to the third location.

Caution: Voltage drop is based on a round trip. Some voltage drop calculators assume a round trip when you plug in the distance, others do not, so the answers (calculated results) can be confusing.

You might save some distance by running a separate circuit directly from the house to the third location instead of branching off from the play house at right angles to go there.

Also note: The number of volts lost in the wires due to voltage drop depends on the amperes drawn at that moment but not on the circuit voltage. So if you lost (example only) 4 volts in the wires which is sligtly more than 3% at 120 volts, you would lose the same 4 volts or slightly more than 1-1/2% at 240 volts. You could put down twice the amperes at 240 volts and suffer the slightly over 3%. Stepping back down to 120 volts with another transformer, the total available amperage is double what went down at 240 volts for a net four times the usable amperage at the far end when you doubled the voltage for the majority of the long wire run compared with no transformers.

Thanks thats helpful. With sizing the transformers do i use the original volts. Or volts after the voltage drop. Ie do i use a 240-120 transformer even though after voltage drop its probably closer to 205? Would i still get 120 out? Or would it also be lower.

Theoretically would it be better to bump to 480 at the pole, take it down with the 8 gauge, and then reverse it to 240....using that to wire a subpanel and branching regular 120 off that? Or is that over complicating it? Is it easier to run 120 down, take the voltage drop (which i think drops it to 98v) and then somehow bump that back up? I assume id lose lots of amps doing that though? What would be the ideal set up and size of transformers? I notice theyre also rates by kva, if i go to small does that just limit my usable power? Or does that blow up?

 

[AllanJ]

Given a 240 to 120 volt (2:1 stepdown) transformer, if 205 volts come in then (theoretically) 102-1/2 volts come out.

The idea of stepping up 120 to 240 volts is so that the voltage drop in the wires is a smaller percentage of 240 compared to percentage of 120 the number of amperes being the same.

(paraphrased from another forum) When you stepped up 120 to 240 at the start and stepped back down to 120 volts at the far end, let's say you needed 2 amps at the far end. It takes only 1 amp at 240 down the trunk line to give 2 amps at the far end. It did take 2 amps at 120 volts into the step up transformer at the origin which became 1 amp down the trunk line). Down the trunk line you suffer the voltage drop for 1 amp as opposed to the voltage drop for 2 amps.

Most household single conductor wire (THWN, etc.) and household cable (Romex, etc.) will handle 600 volts but check yours to be sure.

You would step up to 240 (or to 480 or to 600 possibly requiring a separate permit) at the main house under the main panel if the distance to the shed is great, or step up at the shed under its subpanel if the house to shed distance is small. You can't step up to 480 at the utility pole unless you get a special (commercial; industrial) electrical service fron the power company.

Then step down at the destination.

Shortcut: Take the 240 volts out of the main panel to run a 240 volt only line to the shed. No transformer or special permit needed under that panel. Only 3 conductors needed, neutral, ground, and one hot. Tap off of this 240 volt line at the shed, run that through a transformer (240 to 120/240 models also available) to the shed subpanel. Continue the 240 volt only line to the playhouse where you have another stepdown transformer.

Do not accept/tolerate the voltage drop down the trunk line and step up the 98 volts or so back to 120 at the destination. The voltage drop will vary depending on the load (amperes) drawn at the moment and you don't want the final voltage fluctuating from 120 to 135 or so.

 

[rjniles]

Voltage drop is not a NEC requirement. Max voltage drops occurs when and only when you are pulling max amperage. For the small loads you have, I would wire up what you planned and not worry about it.

Sent from my RCT6A03W13E using Tapatalk

 

[AllanJ]

Do the math.

The electric drill may or may not work from the third location 360 feet and 90 degrees from the play house.

The 8 gauge line, long as it is, may be breakered at 40 amps, but for good taste it should be breakered at a lesser amperage in keeping with voltage drop.

Yet another idea, run the usual 4 wire 8 gauge 120/240 volt run to the shed and think about running 240 only (you will already have had that) to the playhouse with step down transformer out there.

 

[Midgetjoe]

Voltage drop is not a NEC requirement. Max voltage drops occurs when and only when you are pulling max amperage. For the small loads you have, I would wire up what you planned and not worry about it.

Sent from my RCT6A03W13E using Tapatalk

So 8 gauge may be fine by itself if i dont overload it? It should be mostly lights, which could be LED

 

[Midgetjoe]

Given a 240 to 120 volt (2:1 stepdown) transformer, if 205 volts come in then (theoretically) 102-1/2 volts come out.

The idea of stepping up 120 to 240 volts is so that the voltage drop in the wires is a smaller percentage of 240 compared to percentage of 120 the number of amperes being the same.

(paraphrased from another forum) When you stepped up 120 to 240 at the start and stepped back down to 120 volts at the far end, let's say you needed 2 amps at the far end. It takes only 1 amp at 240 down the trunk line to give 2 amps at the far end. It did take 2 amps at 120 volts into the step up transformer at the origin which became 1 amp down the trunk line). Down the trunk line you suffer the voltage drop for 1 amp as opposed to the voltage drop for 2 amps.

Most household single conductor wire (THWN, etc.) and household cable (Romex, etc.) will handle 600 volts but check yours to be sure.

You would step up to 240 (or to 480 or to 600 possibly requiring a separate permit) at the main house under the main panel if the distance to the shed is great, or step up at the shed under its subpanel if the house to shed distance is small. You can't step up to 480 at the utility pole unless you get a special (commercial; industrial) electrical service fron the power company.

Then step down at the destination.

Shortcut: Take the 240 volts out of the main panel to run a 240 volt only line to the shed. No transformer or special permit needed under that panel. Only 3 conductors needed, neutral, ground, and one hot. Tap off of this 240 volt line at the shed, run that through a transformer (240 to 120/240 models also available) to the shed subpanel. Continue the 240 volt only line to the playhouse where you have another stepdown transformer.

Do not accept/tolerate the voltage drop down the trunk line and step up the 98 volts or so back to 120 at the destination. The voltage drop will vary depending on the load (amperes) drawn at the moment and you don't want the final voltage fluctuating from 120 to 135 or so.

How do you run 240 without 4 wires? Doesnt that require hot hot neutral ground? Also arent most subpanels wired with 240? Would we need the transformers?

 

[Oldmaster]

350 ft, 120v, 10 amp.with #8 voltage drop is about 4.5 volts. or 3.66 percent. Typically 3 percent is maximum we tolerate in the he field.

 

[Oldmaster]

It would be more efficient and cost effective to just buy the correct wire size. Transformers will be more expensive and less efficient.

 

[Midgetjoe]

It would be more efficient and cost effective to just buy the correct wire size. Transformers will be more expensive and less efficient.

It seems like I will need only four transformers which are maybe $250 a piece? But if I go from number 8 wire to a number two it would increase from $0.27 a foot to maybe $3 a foot? Over 2000 feet thats a lot

 

[Oldmaster]

Just bought 100 Amp USE. $1.15/ ft, 4 conductors.. priced a 100 amp transformer. $1, 350. Not sure what your looking at but good luck. Plus consider the power loss through the transformers.

 

[AllanJ]

If you are not going to use 480 volts, then you can still get improved performance with 240 volts and no transformers over 120 volts. Not sure whether you will get a full 15 amps at a 120 volt receptacle, you will have to calculate the voltage drop to find out.

Run all 4 wires to all locations with a standard 120/240 volt feed, standard subpanel wiring, standard receptacle wiring, etc. (For example don't use red and white for the shed and black and white for the play house.) Split up the lighting at each location to be approximately half using black and white, the other half using red and white to balance the load on both legs. Have two receptacles, on on each leg, at each location so other things can be plugged in more or less balancing the load on the two legs.

The performance is better still if you use separate home runs (none 120 volt only) from the house to each structure if the total distance to one structure daisy chaining through another structure is much longer compared with going direct. You cut down on the voltage drop here by having a shorter distance.

 

[seharper]

I have a couple very long runs I need to do.

To a shed down my driveway (about 350') that will have [trivial loads] and a couple outlets for the occasional need. Maybe 10 amps max.

Down my field for about 420'...[trivial loads] couple outlets. Then going another 360' [780' total run], [same thing].

OK, that sounds totally doable. I normally use #14 for this sort of thing, but I can make it work with #8 lol.

I thought i had this figured out from digging around online and so bought 7500' of 8 Gauge copper wire (different colors, individual wires that i planned on running in conduit). Now im not so sure with the voltage drop.

Harper's Rule: Buy the wire LAST. (unless you nailed some sweet Craigslist deal.) Don't worry about it, just don't ... do it again.

Honestly, a guy or gal who has the wherewithal to just go out and buy 7500' of #8 copper *on speculation*... that's someone who might put a hot tub, kiln, on-demand water heater, EVSE or 50A RV stand at one of these locations. We will make sure you can do this, since you have the wire.

"But we need to up-size the wire!" Yeah maybe for 200'. Not for this kind of distance. There's a tipping point where you stop throwing cubic metal at it, and pursue other options.

If i wire a 40 amp subpanel (240v, 4 wires) at the shed and the first structure, then run circuits from there (and to the next structure on the downhill run) will that be too much voltage drop to run anything on the 8 gauge wire?

Yeah my problem is, now I'm getting skeptical about your real intent. Nobody puts in a 40A subpanel for a couple outlets and occasional load. I think I'd like to keep some Big Power options in our back pocket. Unfortunately there are choices we'll need to make upfront, since this is conduit not cable. Also I'd like you to fast forward to the Big Power option, so you can see how the conduit and pads need to be placed under those options, so you can plan to be compatible with that for if you ever want to upgrade.


Scenario 1: Cheap-n-Dirty. 120V version.

The problem with this solution is that it requires a white wire in the conduit. The other solutions need a colored wire *instead*. You can't re-mark a white wire to be a hot when it's individual wire in conduit. (unless your AHJ lets you).


Here, we run a Black, White, Green to each outlet location. From there we feed the lights and receptacles. Very straightforward. Since it is one circuit, you do not need grounding rods, which saves a whole lot of rigmarole in the installation. Now let's look at loads.

350' branch: 0.5A normal loads so 0.20% drop using 8 AWG. Add 12.5A of tool load, and you get 5.24% voltage drop.

420' branch: 2.0A normal loads so 0.97% drop using 8 AWG. Add 7A of tool loads, 4.35% drop. Add 12.5A of tool load, and 7.01% drop.

On our 360' extension off that, 1.0A normal loads give 0.41% drop (1.38% total). Add 7A of tool loads, 3.31% voltage drop (totaling 7.66% drop). Add 12.5A of tool loads and 5.59% drop (totaling 12.60% drop).

We're not *supposed* to install more than 8% drop from the main panel. The wire salesmen would certainly prefer we stick to 3% lol. The electrical inspector Will Not Like the 12.60% drop for 12.5A tools, but you could claim your expected load is only 7A and you could just suffer the actual drop. Like I say, we're nowhere near as bad as orange extension cords.


Scenario 2: Cheap-n-dirty: 240V version

Those receptacles are the devil, because it means you need to support any arbitrary 1500W (12.5A) load for that "occasional use". So let's use a 240V/120V stepdown transformer for the rare time when we need 120V tools, That means our 12.5A tool draws 6.25A. That has an amazing effect on voltage drop! Lighting, camera, speaker etc. loads are readily available in 240V.

You wire this scenario exactly like #1. Everything is exactly the same. Except a) you you use NEMA 6-15 outlets (they look almost the same). b) The white wire is now black. And c) choose appliances that have a multi-voltage 120/240V power supply. Which isn't hard these days.

And look what it does to voltage drop!

350' branch: 0.25A normal loads so 0.05% drop using 8 AWG. Add 6.25A of tool load, and you get 1.31% voltage drop.

420' branch: 1.0A normal loads so 0.24% drop using 8 AWG. Add 3.5A of tool loads, 1.09% drop. Add 6.25A of tool load, and 1.75% drop.

On our 360' extension off that, 0.5A normal loads give 0.10% drop (0.34% total). Add 3.5A of tool loads, 0.83% voltage drop (totaling 1.92% drop). Add 6.25A of tool loads and 1.40% drop (totaling 3.15% drop).

Much betta! If you're thinking "wow, all the voltage drops fell by exactly 75%", correct, it falls by (newvoltage/oldvoltage)^2. Ohm's Law x Watt's Law.


Scenario 3: 240V is nice but I want permanent 120V.

"Oh, that'll be easy, just throw the neutral in the pipe and have 120/240V!" No, that won't work at all. The success of 240V depends on balancing the legs. As you can see, the fixed loads are no problem at any voltage. The problem is that "occasional tool" a single, lump sum 1500W load, that is completely lop-sided. It will load one hot, and one neutral, and the other hot won't help at all. This is exactly the problem with scenario #1!

So forget about it. 4 wires in the pipe doesn't buy you a darn thing.

What will make all the difference in the world is a local 120/240V transformer. That forces every load to be balanced on the 240V supply, in fact, supply neutral isn't even needed or present. In the second scenario we stick a handle on it and make you drag it around, but here we'll permanently wire it. And you might be able to do this without going to a subpanel and all that rot... but Imma do subpanels and all that rot. To accommodate the Big Power scenarios, get a 100A subpanel at least. There's no such thing as too many spaces.

We are going to get a bog-standard supply transformer: 120/240V-240/480V. This transformer has a

- Primary that can be jumpered either for 240V or 480V.
- Secondary that can be jumpered for 120/240V split-phase, or twice as much 120V.

You feed the primary 240V, and jumper the secondary - well, either way you like. I don't care. This then goes to a sub-- hold on, this is actually a Main Panel, since the transformer makes it a "separately derived service". Ground rods are mandatory here, and you do install this panel's neutral-ground equipotential bond. It's not a subpanel.

- Size-wise, a typical plug-in tool is 1500 watts, also called 1.5 K VA in the transformer business (VA resembles Watts). So you can use a "1.5 KVA transformer" - but if you do, make sure to jumper it for 120V or it will overload. The 1.5 KVA transformer will give you voltage drops similar to scenario 2.

- If you want 5000 watts at that location, a common size seen for $100 on Craigslist is a "5 KVA transformer", giving 20A @ 240V or 2 legs of 20A @ 120V. Your voltage drop will depend on actual load, but it'll be in proportion to scenario 2. 5 KVA is probably as big as you want to go before voltage drop starts beating you up.


Scenario 4, 480V: Now you're playing with power

The trick with 480V is you have to lay out the conduits and transformer pads so the 480V is entirely contained within the transformer casings, there is no way to access the conduit anywhere else, and there is nothing serviceable inside the transformers. Very few "Danger: 480V" covers, and no reason whatsoever for a homeowner to pop one off. By the way, 480V isn't that scary; Britain brings 416V into people's homes and right into their panels.

Now you have a transformer sitting at the home, being fed by 100A of 240V. That backfeeds the secondary of the transformer. The primary is jumpered for 480V and attached to our long wires. At each location, the conduit pops up *inside* the transformer cowling, and is jumpered straight to the transformer primary. The overcurrent protection is the 100A breaker in the main panel.

Other than that, it's like Scenario 3, with sub---darn it - main panels everywhere.

Calcwise, as you may gather, it falls by (480/120)^2 so all our example voltage drops are now sub-1%. Not even worth calculating. Let's try something big.

A 50A RV stand at the far (780') location that's maxed out at 50A full draw - cooking+dryer+A/C whatever. That is 12,000 watts, or [email protected] Voltage drop calculator says, for [email protected] on #8 wire -- 5.61% drop. Meh, but that's with the RV running at total redline. Normally voltage drop will be lower.


Scenario 5, 600V: Max #8

Mind you, we're starting to spend some serious money on transformers here.

Same thing as above but we are using 120-240/600V transformers. Our nameplate wire capacity is 30,000 watts. Now you're at a 125A breaker trip with 30 KVA transformers. Same as above.

Your RV load at the far end, pulling full 50A about to trip its own breaker, is 3.59% drop.

If you had a 100A on-demand hot water heater at the intermediate location (420'), your voltage drop would be 3.87%.

 

[seharper]

350 ft, 120v, 10 amp.with #8 voltage drop is about 4.5 volts. or 3.66 percent. Typically 3 percent is maximum we tolerate in the he field.

Sounds about right, but the 3% thing is really, really overblown. It is simply not anywhere in Code. People who sell wire, or make commission on wire, or do markups based on wire cost, or who won't be responsible for *what else* will be daisy chained off this in the future, they like 3%.

Here's the thing. Every single one of us has daisy-chained three plain ole orange 16 AWG extension cords to get out to where we gotta go. 300' of those is like 20% drop by the time you hook a typical UL-limit 1500W tool to it. We all do it, there's nothing wrong with it. That's all OP is trying to do here.

OP has 0.5 amps of lights at the shed, and *generously* 1 amp at each of the other locations, but not really, with voltage drops sub-1%. The other use is "occasional orange-extension-cord use". And OP would suffer the voltage drop on those anyway, and nobody would complain if he did. If OP can live with the warbly voltage drop for the very occasional tool-use planned, well, that's OP's business.

It seems like I will need only four transformers which are maybe $250 a piece? But if I go from number 8 wire to a number two it would increase from $0.27 a foot to maybe $3 a foot? Over 2000 feet thats a lot

It would be more efficient and cost effective to just buy the correct wire size. Transformers will be more expensive and less efficient.

Well, procurement is the real trick with transformers. Craigslist around here has 5 KVA transformers for $100-ish pretty regularly; that's enough for my scenario 3.

For my scenario 4, just be uber-patient and watch all the usual auction and surplus channels for a sweet deal, and when you have 2 of them, implement. (if you've already done scenario 3 with the 1.5-5 KVA, you just move a jumper on those).

600V transformers are too odd a duck to be likely to find on those channels, so yeah, so my scenario 5 won't be financially sensible. I just put it in for fun, to show *how much* you can get on your wire.

Ultimately my point is, all this can be incremental (except scenario 1, because that involves a wire change from white to black).

As such, I would make every effort to start at scenario 2, which simply means 240V outlets, procuring 240V lights and appliances, and a portable stepdown transformer.

 

[Midgetjoe]

OK, that sounds totally doable. I normally use #14 for this sort of thing, but I can make it work with #8 lol.



Harper's Rule: Buy the wire LAST. (unless you nailed some sweet Craigslist deal.) Don't worry about it, just don't ... do it again.

Honestly, a guy or gal who has the wherewithal to just go out and buy 7500' of #8 copper *on speculation*... that's someone who might put a hot tub, kiln, on-demand water heater, EVSE or 50A RV stand at one of these locations. We will make sure you can do this, since you have the wire.

"But we need to up-size the wire!" Yeah maybe for 200'. Not for this kind of distance. There's a tipping point where you stop throwing cubic metal at it, and pursue other options.



Yeah my problem is, now I'm getting skeptical about your real intent. Nobody puts in a 40A subpanel for a couple outlets and occasional load. I think I'd like to keep some Big Power options in our back pocket. Unfortunately there are choices we'll need to make upfront, since this is conduit not cable. Also I'd like you to fast forward to the Big Power option, so you can see how the conduit and pads need to be placed under those options, so you can plan to be compatible with that for if you ever want to upgrade.


Scenario 1: Cheap-n-Dirty. 120V version.

The problem with this solution is that it requires a white wire in the conduit. The other solutions need a colored wire *instead*. You can't re-mark a white wire to be a hot when it's individual wire in conduit. (unless your AHJ lets you).


Here, we run a Black, White, Green to each outlet location. From there we feed the lights and receptacles. Very straightforward. Since it is one circuit, you do not need grounding rods, which saves a whole lot of rigmarole in the installation. Now let's look at loads.

350' branch: 0.5A normal loads so 0.20% drop using 8 AWG. Add 12.5A of tool load, and you get 5.24% voltage drop.

420' branch: 2.0A normal loads so 0.97% drop using 8 AWG. Add 7A of tool loads, 4.35% drop. Add 12.5A of tool load, and 7.01% drop.

On our 360' extension off that, 1.0A normal loads give 0.41% drop (1.38% total). Add 7A of tool loads, 3.31% voltage drop (totaling 7.66% drop). Add 12.5A of tool loads and 5.59% drop (totaling 12.60% drop).

We're not *supposed* to install more than 8% drop from the main panel. The wire salesmen would certainly prefer we stick to 3% lol. The electrical inspector Will Not Like the 12.60% drop for 12.5A tools, but you could claim your expected load is only 7A and you could just suffer the actual drop. Like I say, we're nowhere near as bad as orange extension cords.


Scenario 2: Cheap-n-dirty: 240V version

Those receptacles are the devil, because it means you need to support any arbitrary 1500W (12.5A) load for that "occasional use". So let's use a 240V/120V stepdown transformer for the rare time when we need 120V tools, That means our 12.5A tool draws 6.25A. That has an amazing effect on voltage drop! Lighting, camera, speaker etc. loads are readily available in 240V.

You wire this scenario exactly like #1. Everything is exactly the same. Except a) you you use NEMA 6-15 outlets (they look almost the same). b) The white wire is now black. And c) choose appliances that have a multi-voltage 120/240V power supply. Which isn't hard these days.

And look what it does to voltage drop!

350' branch: 0.25A normal loads so 0.05% drop using 8 AWG. Add 6.25A of tool load, and you get 1.31% voltage drop.

420' branch: 1.0A normal loads so 0.24% drop using 8 AWG. Add 3.5A of tool loads, 1.09% drop. Add 6.25A of tool load, and 1.75% drop.

On our 360' extension off that, 0.5A normal loads give 0.10% drop (0.34% total). Add 3.5A of tool loads, 0.83% voltage drop (totaling 1.92% drop). Add 6.25A of tool loads and 1.40% drop (totaling 3.15% drop).

Much betta! If you're thinking "wow, all the voltage drops fell by exactly 75%", correct, it falls by (newvoltage/oldvoltage)^2. Ohm's Law x Watt's Law.


Scenario 3: 240V is nice but I want permanent 120V.

"Oh, that'll be easy, just throw the neutral in the pipe and have 120/240V!" No, that won't work at all. The success of 240V depends on balancing the legs. As you can see, the fixed loads are no problem at any voltage. The problem is that "occasional tool" a single, lump sum 1500W load, that is completely lop-sided. It will load one hot, and one neutral, and the other hot won't help at all. This is exactly the problem with scenario #1!

So forget about it. 4 wires in the pipe doesn't buy you a darn thing.

What will make all the difference in the world is a local 120/240V transformer. That forces every load to be balanced on the 240V supply, in fact, supply neutral isn't even needed or present. In the second scenario we stick a handle on it and make you drag it around, but here we'll permanently wire it. And you might be able to do this without going to a subpanel and all that rot... but Imma do subpanels and all that rot. To accommodate the Big Power scenarios, get a 100A subpanel at least. There's no such thing as too many spaces.

We are going to get a bog-standard supply transformer: 120/240V-240/480V. This transformer has a

- Primary that can be jumpered either for 240V or 480V.
- Secondary that can be jumpered for 120/240V split-phase, or twice as much 120V.

You feed the primary 240V, and jumper the secondary - well, either way you like. I don't care. This then goes to a sub-- hold on, this is actually a Main Panel, since the transformer makes it a "separately derived service". Ground rods are mandatory here, and you do install this panel's neutral-ground equipotential bond. It's not a subpanel.

- Size-wise, a typical plug-in tool is 1500 watts, also called 1.5 K VA in the transformer business (VA resembles Watts). So you can use a "1.5 KVA transformer" - but if you do, make sure to jumper it for 120V or it will overload. The 1.5 KVA transformer will give you voltage drops similar to scenario 2.

- If you want 5000 watts at that location, a common size seen for $100 on Craigslist is a "5 KVA transformer", giving 20A @ 240V or 2 legs of 20A @ 120V. Your voltage drop will depend on actual load, but it'll be in proportion to scenario 2. 5 KVA is probably as big as you want to go before voltage drop starts beating you up.


Scenario 4, 480V: Now you're playing with power

The trick with 480V is you have to lay out the conduits and transformer pads so the 480V is entirely contained within the transformer casings, there is no way to access the conduit anywhere else, and there is nothing serviceable inside the transformers. Very few "Danger: 480V" covers, and no reason whatsoever for a homeowner to pop one off. By the way, 480V isn't that scary; Britain brings 416V into people's homes and right into their panels.

Now you have a transformer sitting at the home, being fed by 100A of 240V. That backfeeds the secondary of the transformer. The primary is jumpered for 480V and attached to our long wires. At each location, the conduit pops up *inside* the transformer cowling, and is jumpered straight to the transformer primary. The overcurrent protection is the 100A breaker in the main panel.

Other than that, it's like Scenario 3, with sub---darn it - main panels everywhere.

Calcwise, as you may gather, it falls by (480/120)^2 so all our example voltage drops are now sub-1%. Not even worth calculating. Let's try something big.

A 50A RV stand at the far (780') location that's maxed out at 50A full draw - cooking+dryer+A/C whatever. That is 12,000 watts, or [email protected] Voltage drop calculator says, for [email protected] on #8 wire -- 5.61% drop. Meh, but that's with the RV running at total redline. Normally voltage drop will be lower.


Scenario 5, 600V: Max #8

Mind you, we're starting to spend some serious money on transformers here.

Same thing as above but we are using 120-240/600V transformers. Our nameplate wire capacity is 30,000 watts. Now you're at a 125A breaker trip with 30 KVA transformers. Same as above.

Your RV load at the far end, pulling full 50A about to trip its own breaker, is 3.59% drop.

If you had a 100A on-demand hot water heater at the intermediate location (420'), your voltage drop would be 3.87%.

This is helpful thanks. To clarify, i dont have any tools or equipment than needs 240v, just all regular 120v. Lights, and speakers, drill etc. So would only need 240 if i need it to mitigate voltage drop.

I mentioned the 40 amp subpanel because its the max on the 8 gauge, but i probably only need 10a at each structure.

Of your options what is the easiest thing to wire that will functionally work?

 

[seharper]

Shortcut: Take the 240 volts out of the main panel to run a 240 volt only line to the shed. No transformer or special permit needed under that panel. Only 3 conductors needed, neutral, ground, and one hot. Tap off of this 240 volt line at the shed, run that through a transformer (240 to 120/240 models also available) to the shed subpanel. Continue the 240 volt only line to the playhouse where you have another stepdown transformer.

Egg zactly. I know I kinda doubled over much of this in my own post, because I was making it in levels, but yeah. Everything you said.

So many things these days have dynamic switching power supplies that can take anything between 100-240V. So why not just power them straight off 240V. The only reason to think about 120V anymore is receptacles.