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300 feet of wire

Posted by gator627 (My Page) on
Sun, Aug 1, 10 at 22:56

I am wanting to run power to a outshed on the farm. Approx 300ft. What size wire do I need for 220 amp and can I run it above ground or below ground?


Follow-Up Postings:

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RE: 300 feet of wire

Hopefully you mean 220V not 220A.

You need to determine how much power (amperage) you need at the shed before wire size can be determined... a few lights and a receptacle will require a lot less than a full blown workshop

Underground would be my choice.


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RE: 300 feet of wire

The NEC restricts sheds to a single circuit unless they have a sub-panel.

A sub panel in a separate structure requires a grounding electrode system.

Burial depth depends on hot the wiring is protected and what it is running under.

Overhead has clearance rules also.


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RE: 300 feet of wire

4 cond also required. (hot, hot, neutral, ground.)
I would install a 50a panel with 2awg wire, personally, but it may be required to be thicker. you do not want more than 5% volt drop.


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RE: 300 feet of wire

Smithy:

I am planning to go on a trip in my car. How many gallons of gasoline will I need?


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RE: 300 feet of wire

This guy is in Canada and depending on what is in the 'outshed' he probably doesn't Need sep. grounding(of course, he could if he wants to do it that way, which may he cheaper depending on how he runs the wire).

Either way we need more info before we can recommend a square D QO panel for him ;)


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RE: 300 feet of wire

Smithy wrote: "I would install a 50a panel with 2awg wire, personally, but it may be required to be thicker. you do not want more than 5% volt drop."

ontariojr wrote: "This guy is in Canada.."

Funny that. Here in the U S of A we figure that a 300' run of #4AWG CU carrying all of 50 amps in a 120/240V system will yield a voltage drop of about 3.9%. The only explanation I can come up with is that Canadian voltage must drop more than U.S. voltage and Smithy must have factored that into his expert advice.

Do you fellers up north follow Ohm's Law like we 'Merkins do or did Canada pass their own version of the law? Just wondering. :-)


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RE: 300 feet of wire

Sorry to disappoint, but smithy is in the good old US of A! I cannot keep him.

I meant the OP was Canadian-and my advice was acurate.

Cheers


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RE: 300 feet of wire

If you will be operating any motors in the shed the 50 A may not be correct for the motor starting surge (like a table saw or other cutting equipment).

Allowing excessive voltage drop on motor start-up is a good way to damage motors.


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RE: 300 feet of wire

"I meant the OP was Canadian-and my advice was acurate.

'Twas never in question, ontariojer. Was just funnin' with the youngster.

Cheers back at ya. (Too bad you can't keep him though.) :-)


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RE: 300 feet of wire

"Here in the U S of A we figure that a 300' run of #4AWG CU carrying all of 50 amps in a 120/240V system will yield a voltage drop of about 3.9%. Do you fellers up north follow Ohm's Law like we 'Merkins do or did Canada pass their own version of the law? Just wondering."

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Well... technically, Ohm's law only applies to DC electricity. AC, over time, for a purely resistive load appears behave like DC so is the reason why Ohm's law can be applied. However, for long runs of high amp current where motors, solenoids, etc might involved then simple Ohm's law calculations can get you into a lot of trouble. It's no longer just the real power being used, but the apparent power caused by the reactive component. The answer is highly dependent upon the type of load. You either have to stick to tables generated by engineers or understand the proper calculations.

In any case, if the OP meant 220 amps, a pair of transformers at either end would lessen the wire requirements considerably.


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RE: 300 feet of wire

i was assuming resudential power tools like the ones from l's, running on 120v, 15a. don forget the sqd panel.


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RE: 300 feet of wire

"Well... technically, Ohm's law only applies to DC electricity. AC, over time, for a purely resistive load appears behave like DC so is the reason why Ohm's law can be applied."

This is just WRONG.

Ohms law applies to AC, DC, and just about everything else.

In a DC circuit the value of current is constant for a fixed voltage and load.

In an AC circuit the current is instantaneously related by phms law, and if you use the correct units to measure (Root Mean Square, RMS) it produces a consistent system that works just fine.

As the frequency of an AC waveform increases the simplifed version of ohms law starts to not correctly deal with loads, especially non-resistive loads.

The full version of ohms law works just fine though at any frequency.


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RE: 300 feet of wire

"Ohms law applies to AC, DC, and just about everything else."

Sorry, you have no idea what you are talking about. Period.


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RE: 300 feet of wire

this link might be useful. you do not want more than 5% drop.

Here is a link that might be useful: voltage drop calculator


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RE: 300 feet of wire

Bernise, yoy are wrong. It's got squat to do with RMS. All RMS does is indicate how your meter is indicating what the voltage is (either Peak to peak or some average of the wave form volatge).

The problem is that RESISTANCE is only part of the relationship between voltage and current with AC. As soon as you have any REACTANCE that has to be accounted for in an AC circuit. The voltage and current wave forms may not be in phase.


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RE: 300 feet of wire

"The problem is that RESISTANCE is only part of the relationship between voltage and current with AC. As soon as you have any REACTANCE that has to be accounted for in an AC circuit."

Where are the KVAR trolls when you really need them?

(Sorry, Ron, just kidding.)


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RE: 300 feet of wire

what is a kvar?


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RE: 300 feet of wire

""Ohms law applies to AC, DC, and just about everything else."

Sorry, you have no idea what you are talking about. Period."

Time to attend a lot more classes.

Even heard of complex impedance?

How about phase shift?

Fourier & Laplace transforms? (You can then even analyze circuits with multiple frequencies present, from DC to whatever is needed, all at the same time. Superposition works nicely).

You are the one that has no idea what you are talking about.

Ohm's law drops out of the Maxwell equations as a simplification.

You have simplified Ohm's law even further out of ignorance.


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RE: 300 feet of wire

try this

Here is a link that might be useful: voltage drop calculator


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RE: 300 feet of wire

OK, i have enjoyed the dialogue, quite funny at times. especially "I am going on a trip in my car, how much gass will I need" But now another question along the same lines with a little more detail that may get an answer from one of these engineers.
At the end of the 300 feet i want to put a sq - d panel with a 30 amp 220v breaker and a 20amp 110v breaker
to run two different pumps to pull water from a pond for two acres of clover for my beehives.
What size of cable do I need. will be run above ground though PVC. Will that work in OKlahoma USA?


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RE: 300 feet of wire

Two things.

You would run individual conductors in conduit, not cable.

And what do you mean it will be run above ground???How do you propose to do this?


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