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New to electrical work and I had recently run a 12-2 UF wire from my basement about 95' to a shed. I plan on using a window mounted Air conditioner, so I figured making a 20 amp circuit would be enough. Now I'm finding out that at 95' I'm losing slightly over 5% in droppage. Is that amount of drop going to problematic/dangerous while running the A/C. Thanks in advance!
 

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Shazbot!
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Is there going to be anything else on the circuit?
 

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New to electrical work and I had recently run a 12-2 UF wire from my basement about 95' to a shed. I plan on using a window mounted Air conditioner, so I figured making a 20 amp circuit would be enough. Now I'm finding out that at 95' I'm losing slightly over 5% in droppage. Is that amount of drop going to problematic/dangerous while running the A/C. Thanks in advance!
Well that's a relief. Thought the post was 12 gauge wired to shed. That'd be a whole different problem.
 

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If it was me,I would run nothing smaller than #10. How much of cost difference would it be,also lower your voltage the higher your amps.
 

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https://www.powerstream.com/Wire_Size.htm <--- handy widget, scroll down page to losses calculator.

Interesting that they call 9.3 Amps for 12AWG Maximum amps for power transmission versus 15 Amps for 10AWG (but a disclaimer says it's a "rule of thumb".

I am in the fat copper camp myself - I got pshaww'd and overruled when I tried to get my brother to heavy-up a wire run to an outbuilding - then fast forward a few years and he's thinking solar panels to sell power back to the utility and putting them on that outbuilding.... I ran the numbers and he'd be using almost 10% of the solar power heating his 'economized-on-install copper wires' back to the house, across the house itself just to reach the power meter...

Also - if there is a flicker or brown-out in the powerco supply the effects will be worse at the end of that run... if voltage sags then current rises to compensate, the higher the current then the higher the losses in the wire...
 

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Shazbot!
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If it was me,I would run nothing smaller than #10. How much of cost difference would it be,also lower your voltage the higher your amps.
I thought the OP was asking after already running the 12 gauge. If not, I agree, always run a bigger wire than you think you need.
 

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A rule of thumb is to go to the next size (smaller gauge number) up for every 100 feet of run to have the same amps circuit. Conversely this means that a 100 foot run of a given gauge wire results in the next lowest amperage compared to shorter runs. You have run 12 gauge which supports a 20 amp breaker in shorter runs so it supports a 15 amp breaker in the 100 foot run.

Next question is what size AC are you going to run? Bigger BTU ACs need more amperage. A 15 amp circuit will run a 5000 or 6000 BTU window unit no problem. For a 12000 BTU window AC the 15 amp circuit will barely work. Nothing bigger will work on your circuit.

https://www.hunker.com/13407208/current-draw-of-air-conditioners

For future reference, I would always run a 3 conductor plus ground to any outbuilding if there was room in the breaker panel for a 240 volt breaker. This provides 240 volt if you need it and/or two 120 volt circuits. The extra cost of the 3 wire with ground is minimal and you won't wind up wishing you had more power in the building.
 

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Licensed electrician (retired) here. I agree with those who say 12/2 will do the job but 10/3 for future as the previous guy says is the way to go if not already run. In addition if run underground and thus trench dug I always run it through a bit of 1" polly pipe to cover change of plans and a little extra protection. Plans change and Murfeys Law is always in full effect I have found!
 

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You could use a 220 volt circuit and 220v AC unit and cut the amperage and lose in half. You would not be able to run anything 110 v in the shed though.
 

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That was kind of foolish economizing, saved a penny will cost a dollar to fix right some day, but it will work sorta for what you say you will be doing.

someday you will want a light, or run a drill, or something as well, and just keep pushing the limits.

Too bad. Electrical should be done right the first time, just a little planning.

Paul
 

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You could use a 220 volt circuit and 220v AC unit and cut the amperage and lose in half. You would not be able to run anything 110 v in the shed though.
This statement is true only if you ran 12/2 with ground as the OP did. Then you can run 240 volts, and only 240 volts, if you make the white wire a hot wire. You have to color the ends of the white wire black so the next person knows it's hot. If you run 12/3 with ground you can have both 120 and 240 volt circuits in the shed.
 
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