Hi all,
I'm looking for some electrical advice. I want to have 2 seperate 20a 120v circuits on a post outdoors using 8/3 UF. The run is about 200 ft. Can I run the 8/3 off a 2 pole breaker and split it to (2) 120v outdoor rated GFCI receptacles once I get to the post? I probably need a means of disconnect at the post too? Thoughts?
For that distance you will need 6/3 wire.
Other than that you should be good.
From memory you want less than 3% voltage drop, there are calcs online. You'll need 4 wires total, for example 6/3 with ground.
This calc is a favorite of mine for this: https://www.calculator.net/voltage-drop-calculator.html
At that distance, even 6/3 is a tad iffy.
The other thing to consider is you will be sharing a neutral on both circuits. This is fine for the ampacity of the wire is more than enough.
However, at that distance the loss will go up if you run both 20 amp circuits at max current. If this is rare, then the loss should be acceptable.
There are 2 concepts here, the loss of voltage and efficiency. The second is the safety of the breaker protecting the wire ampacity, which you are fine with your choice. A larger wire gage will just get less loss.
Thank you all for the replies. When I figured the 8 ga. Wire, I was planning on 16a max load on each circuit. 80% of the 20a breaker. It looked like it was right on the edge of max voltage drop at 16a. Actually the largest, potentially constant,load should be no more than 12.5a.
As far as the mechanics of it, I would protect with a twin 20a breaker, feed the circuit with UF wire, but I'm unsure what the correct practice should be at the other end. Do I simply need 2 20a outdoor rated GFCI receptacles in a weatherproof enclosure?
That's what I've done. I've also run at more than 3% voltage drop, way out on drop cords sawing. Not saying it's good atall but those tools still run. Just like in a plumbing system when you don't have a tap open it reads full pressure, when you open a tap that's when you see the pressure drop. You'll read full voltage until you hit the trigger. I've had to decide whether I want to see what I'm sawing or just saw on occasion. Dave, for sharing the neutral, those legs are 180 degrees out of phase in my mind, is it really clipping the capacity ???.
I am going to price the 6/3 UF so if I needed to pull more power from the circuits in the future, it might be worth the extra $$$$ to do it right the first time!
Quote from: Don_P on October 09, 2018, 06:09:20 AM
That's what I've done. I've also run at more than 3% voltage drop, way out on drop cords sawing. Not saying it's good atall but those tools still run. Just like in a plumbing system when you don't have a tap open it reads full pressure, when you open a tap that's when you see the pressure drop. You'll read full voltage until you hit the trigger. I've had to decide whether I want to see what I'm sawing or just saw on occasion. Dave, for sharing the neutral, those legs are 180 degrees out of phase in my mind, is it really clipping the capacity ???.
You really are not "clipping" capacity as the wire has more capacity than the breaker, which is good! To answer what I think your question is back to concepts of wiring. There are always at least 2 losses. The circuit sharing a neutral will have more loss at higher currents and just because they are out of phase that loss can still be there. Not a big deal here but good to know because there are people who do this with 2 in phase legs and the loss will be much higher. As you said, if this is a saw that is intermittent then no problem. If it was (2) 1500 watt heaters there would be more loss and you would use more grid or battery power to run the devices.