Voltage question

Spook

Well-known Member
A neighbor wants to run power to a shed 300 ft from his house. He thinks #10 wire with a 30 amp breaker will be ok? I think he needs a box in the shed, and some heavier wire, maybe a #6 or #4?
 
(quoted from post at 14:26:38 10/16/14) A neighbor wants to run power to a shed 300 ft from his house. He thinks #10 wire with a 30 amp breaker will be ok? I think he needs a box in the shed, and some heavier wire, maybe a #6 or #4?
ike diapers.....it depends. Does he want a light or does he want to run a 400amp welder?
 
(A) "He thinks #10 wire with a 30 amp breaker will be ok?"

QUESTIONS: How many conductors is he running????Is the wire suitable for Direct Burial in Earth such as type UF Cable??? Or is he using conduit (I sorta doubt that) or aerial conductors??? Is he ONLY going to need 120 volts???? Of course, how many total amps is required????

GUESS WHAT it may well be okay, but before Billy Bob and Bubba have a calf and yell that wire isn't big enough or claim to know the answer, read below:

In order to calculate the voltage drop, WHICH MAY? BE A PROBLEM AND PERHAPS? UNACCEPTABLE,

WE NEED TO KNOW THE CURRENT and no one can calculate voltage drop UNLESS WE KNOW THE CURRENT!!!!

THAT BEING SAID, if he has much of a load at all out at that shed and its 300 feet away from the service panel HE MAY? NEED BIGGER WIRE but again, no one can say that not knowing his load. HOWEVER unless his load is very small, the voltage drop over that 300 feet run may? be OUT OF TOLERANCE (SUBJECT TO LOAD REMEMBER)

Its just that so many jump all over a question like this (electrical questions get a ton of responses, including mine, as were all just trying to help and well meaning and that's a good thing in my opinion) with a supposed correct answer, WITHOUT HAVING THE FACTS!!!!!!!!!!!

(B) "I think he needs a box in the shed, and some heavier wire, maybe a #6 or #4?"

You MAY be right!!!! If he has more then an outlet and maybe a light or two out in that shed (SUBJECT TO load and lights or receptacles etc., sorry I forget the NEC requirement for a panel out there, I know one may NOT be required for only something like a light or an outlet) A SMALL SUB PANEL may indeed be required by the NEC or local jurisdiction or authority. I'm NOT saying it wont work otherwise, I'm ONLY saying to size the wire and calculate the voltage drop WE NEED TO KNOW THE CURRENT.

ALSO If he indeed needs a panel out there, it should be configured as a Sub Panel with separate and isolated Neutral and Equipment Ground Busses.

ALSO a buildings electrical service requires proper earth Grounding.

ALSO the NEC has some rules (as I recall, no warranty) in instances where perhaps the EXACT load isn't known an engineering assumption is permitted, but subject to the actual loads and wire and conduit sizes and other factors. What I'm saying is there are rules for say the maximum number of duplex outlets on a single 120 volt 20 amp branch circuit EVEN IF THE ACTUAL LOAD IS UNKNOWN. So perhaps a panel may or may not be required out there (depends on how many outlets or lights as I recall) and a certain amperage is to be used in calculations SO MAYBE A MINIMUM WIRE SIZE (to allow voltage drop to be acceptable) CAN BE DETERMINED ABSENT the actual load being known????

TELL US THE CURRENT AND WE CAN GO TO A CHART AND CALCULATE THE VOLTAGE DROP AND THEN WE CAN REALLYYYYYYYYYYY SIZE THE WIRE !!!!!!!!!!


HERES AN ENGINEERING APPROACH:

If I were going to install wiring out to a shed, I think I would first assign a value of the MAX current such as say 16 amps, then calculate the voltage drop using voltage drop charts based on the max current draw of 16 amps, THEN THE WIRE CAN FINALLY BE PROPERLY SIZED so the voltage drop is an acceptable level...In my opinion that's how to approach his question and the design.

Nuff said

John T Too darn long retired EE and forget the NEC, so no warranty whatsoever, wire it as he pleases.............
 
It's actually a valid intended question, I don't mind them, its just that its one that cant be answered with the given information. Hey we all try our best but the impossible questions just take longer lol I'm sure theres a gazillion sheds out there with 10 or even 12 gauge ran to them and a small tool or appliance or a few lights might work fine, its just that if you try to run say a motor at low voltage you could end up damaging something.

I probably over react some times lol.

John T
 
That's a good approach to his question. Hey if we don't know the load you at least gave him some good information that may make him realize the limitations of small wire over long distances. I always forget what the acceptable voltage drop is, too long since I practiced.

John T
 
This one is a lot like what I have. 100 or so feet to power my horse barn and goat house. #10 wire 2 wires plus ground. All it does is power a few lights and once in a while a saw or drill. Been hooked up for 20 plus years now and doing ok. Sure would not run a welder on it or try to use it for 220 volts but for a simple 110 volt circuit works just fine but I do have a breaker box in the barn and hooked up to a 15 amp breaker in my shop so breakers are smaller then what the wire calls for
 
Find out what all will be powered in the shed, add up the amperage, round up the number a little for future expansion, then plug the info into this calculator...


http://www.calculator.net/voltage-drop-calculator.html
 
Yep, its like I said, I'm sure there are a lot of similar situations (like yours) where things still "work", but "working" and being safe and proper and the best correct way of doing it are two different things. AGAIN IT DEPENDS ON THE LOAD as to how well it "works".

A three conductor circuit can still be used for 220 volts, and in fact, it only takes half the current given the same wattage WHICH ACTUALLY MAKES IT BETTER if it were run at 220 and was a tool or appliance that could utilize it. The three conductors (if 220 is used and no 110) would be the two hot Ungrounded phase conductors, L1 & L2, and the bare/green Equipment GroundING Conductor.

John T
 
Plus in ALL my buildings I have a ground rod tied into the breaker boxes so that if something odd happens I still have a true earth ground. Ground rods are 10 foot long and at least 5 feet is in the ground if not more
 
Good for you Rich, if its a remote out building with a sub panel fed from your main that has separate and isolated Neutral and Ground Busses, a Grounding Electrode is required (A buildings electrical service, be it a main or a sub panel for that matter, still requires Grounding). As far as it being "Tied into the breaker boxes" where its tied depends on if its a main or a sub.

John T
 

As previously stated. A 60amp service in the shed would be a minimum. This would operate a 6-50R welder plug, lights, beer fridge with a couple of circuits using 6-15/20 (T-Slot) receptacles.
How close is the shed to the utility power pole with the electrical meter?
 
I think he just wants to run a couple lights and a outlet or 2. I was just surprised that he had a 30 amp breaker on it.
 
(quoted from post at 23:07:20 10/16/14) I think he just wants to run a couple lights and a outlet or 2. I was just surprised that he had a 30 amp breaker on it.

That is the way it starts out, just need a light and an outlet. pretty soon it's an air compressor, fridge, microwave, washing machine and dryer for work clothes, water heater, power tools, air conditioner, portable heaters and a welder.
On the entire cost of the job, upping the wire size a couple from 30amp to 60amp is not particularly costly.
 
For only a couple lights and an outlet, I'm fairly sure a panelboard IS NOT REQUIRED but he would have to check the latest NEC and his local authority (I forget). If its only a few amps he might get by with the 10 gauge you mentioned and not exceed voltage drop. HOWEVER in my opinion if you're going to the trouble to run wire out there, its not that much harder (sure a bit more expensive) to run bigger wire and have a small panel out there. His money his choice.

John T
 
Rich;

You say you wouldn't use it for 220 volt operation, which suggests to me that you don't choose to, but could. That means that your 10 gauge wire is supplying 220 volts, right? Two hot wires and a ground. But you only run lights and the occasional saw or drill there, 110 volt appliances. That means that you have to use the ground as a neutral/return, yet neither John T. nor buickanddeere got on your case about it. Do you think that's because they didn't notice it, or is there something about using the ground as your neutral in a distant location that makes it acceptable?

Stan
 
Stan, I sort of (right or wrong??) read it that he was ONLY using 120 volt loads NOT any 240 nor BOTH out of the same box (if so more wires needed) , but that he just meant he wouldn't try to run anything on 240???? However, as you know, if he had the choice/option to run a tool or appliance at 240 instead of 120 it would only draw 1/2 the current. It seems he may be thinking a 240 tool is somewhow more difficult or takes bigger wire, when actually 240 uses less current and you can get by with smaller wire. Hard to say, I'm NOT a mind reader lol I do the best I can with the info given and still often mess up.

By the way under the old 3 wire system/code to remote 120/240 panels they only ran the 3 wires, in which case Neutral current was carried back to the main panel in the Ground, but the new code cured that.

Fun chattin at ya

John T
 
It is a simple 110 circuit and 3 wire if it was 220 back when it was put in that was still what code said but not any more.
 
Being a former Navy E.T. and a form maintenance electrician yes I understand 110, 220, and 480 3 phase. Of course when I was doing both those jobs it was the old 3 wire system not this new 4 wire. For my barn I have no need for more then 110 circuits
 
John;

I was thrown off by Rich saying that he wouldn't try to use it for 220 volts because I know that Rich knows enough about the subject to know that he doesn't have to say that he wouldn't do something that isn't possible anyway. If you don't have 220 volts then it goes without saying that you aren't going to use 220 volts. But if you have 220 volts supplied by two hot lines and an equipment ground, then you can use 120 volts by using the ground as your neutral---it's wrong, but it's possible.

But the answer to my question is that you and buickanddeere didn't jump in to advise Rich against doing it that way because you read what he posted differently, and correctly, from the way I read it.

Stan
 

Stan you seem offended that running neutral current on a ground wire wasn't brought to attention.
I'll read through again but the impression was a proper four wire was going to be routed.
One would be daft to do all that work for one lousy 15 amp, 120V circuit. At the very least 120/240 at 20 amps to operate two separate T-slot receptacles and in the future a 240V compressor or heater.
Run the lights all on one circuit and the tools on the other. Less light dimming when starting tools. Not left in the dark either if a tool trips a breaker.
 
buickanddeere;

I wasn't offended, only mildly surprised. But I think maybe we're not talking about the same thing. My question was in regards to old's installation, not that of the original poster. In his description of his situation, old said that it had been that way for 20 years. My reading of that would be that he's saying it's fine the way it is, and he has no plans to change it. Of course it's fine as it is if it's a normal 120 volt circuit---hot/neutral/ground. But old mentioned not running 240 there, which I took to mean that it was at least possible that he meant that he could, but didn't. If he could, then there wouldn't be a neutral because he said it was a 3 wire installation, two wires plus ground. What I said about you and John T. not getting on his case was meant to be something like an inside joke for regular readers on this site. You, in particular, are known to have little patience with people who do things that could endanger others out of ignorance, cheapness, or indifference.

Stan
 
(quoted from post at 19:49:20 10/17/14) buickanddeere;

I wasn't offended, only mildly surprised. But I think maybe we're not talking about the same thing. My question was in regards to old's installation, not that of the original poster. In his description of his situation, old said that it had been that way for 20 years. My reading of that would be that he's saying it's fine the way it is, and he has no plans to change it. Of course it's fine as it is if it's a normal 120 volt circuit---hot/neutral/ground. But old mentioned not running 240 there, which I took to mean that it was at least possible that he meant that he could, but didn't. If he could, then there wouldn't be a neutral because he said it was a 3 wire installation, two wires plus ground. What I said about you and John T. not getting on his case was meant to be something like an inside joke for regular readers on this site. You, in particular, are known to have little patience with people who do things that could endanger others out of ignorance, cheapness, or indifference.


Stan

Stan, thanks for the appreciation or at least I'll take it that way. It can be a thankless task trying to make the world a better place.
 
It was meant as appreciation. Your modesty (or irony) aside, there are worse things a person can do in life than try to make the world a better place. And just so it won't be a totally thankless task, thanks.

Stan
 
(quoted from post at 22:01:21 10/16/14)
(quoted from post at 23:07:20 10/16/14) I think he just wants to run a couple lights and a outlet or 2. I was just surprised that he had a 30 amp breaker on it.

That is the way it starts out, just need a light and an outlet. pretty soon it's an air compressor, fridge, microwave, washing machine and dryer for work clothes, water heater, power tools, air conditioner, portable heaters and a welder.
On the entire cost of the job, upping the wire size a couple from 30amp to 60amp is not particularly costly.

If going under ground I always encourage using conduit, and also over sized conduit, so when someone wishes that they had more power/amps, and/or voltage, you can then change to larger wire and/or more wires.

Dusty
 

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