Wire awg for long run

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junquecol

Bruce
User
I NEVER use UF cable any more! I always bury the grey PVC pipe. Use a minimum of 3/4". You can pull regular NM through it, though I prefer THHN. The cost of pipe, and wire is often less than the UF cable. Remember that a piece of tape can change the color of a wire. Bury your pipe, vacumm a "rat" through it, connect to a pull rope to string on "rat". Pull rope back through pipe, and then attach the wires to be pulled. The string on the "rat" will tell you how long to get wire. Be sure to add at least ten feet for connections at each end. If you should ever have to add another circuit, or change conductors, you already have a hole under the ground.
 

Glennbear

Moderator
Glenn
I NEVER use UF cable any more! I always bury the grey PVC pipe. Use a minimum of 3/4". You can pull regular NM through it, though I prefer THHN. The cost of pipe, and wire is often less than the UF cable. Remember that a piece of tape can change the color of a wire. Bury your pipe, vacumm a "rat" through it, connect to a pull rope to string on "rat". Pull rope back through pipe, and then attach the wires to be pulled. The string on the "rat" will tell you how long to get wire. Be sure to add at least ten feet for connections at each end. If you should ever have to add another circuit, or change conductors, you already have a hole under the ground.
BTDT with new shop:wsmile:
 

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junquecol

Bruce
User
Glenn, from the picture, it looks like your hots and neutral are #6. If so, you ground only needs to be a #10. If hots and neutral are # 4, then ground only needs to be #8. This is often over looked by home owners. Can't really tell from the picture if you downsized the grounds. Bruce
 

Glennbear

Moderator
Glenn
Glenn, from the picture, it looks like your hots and neutral are #6. If so, you ground only needs to be a #10. If hots and neutral are # 4, then ground only needs to be #8. This is often over looked by home owners. Can't really tell from the picture if you downsized the grounds. Bruce
100 amp circuit feeding subpanel, USE AL wire 2-2-2-4 . Even with the upsizing because of AL, was still much cheaper than CU. All connections coated with antioxidant. Shop wiring is all 12 NM with the exception of 1O ga THHN feeding 4000W 240V heater and 6GA for welder outlet. Whole job done beyond NEC mininums. :wwink:
 

cpowell

Chuck
Senior User
I'm calculating a 4 volt drop with 10AWG and a 6 volt drop with 12 AWG for a 200 ft run, using standard copper resistivity at 20 amps. I have also looked up wire resistance/ft (Ohm/ft) values online and get similar results.

v = i*R for 200 ft solid copper, 10AWG, R = 0.1944 Ohms, i = 20 Amps
so, v = 20 * 0.1944 = 3.89 volts (roughly 4 volts)

for 200 ft solid copper, 12AWG, R = 0.3090 Ohms,
v = 20 * 0.3090 = 6.18 volts (roughly 6 volts)

Forget the transformer and any 2 percent drop concerns.


Chuck
 
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