8 AWG current capacity

I have found several hundred feet of 8 AWG wire that I would like to use to bring electricity to my shop that is 200' from my house. At the
moment I use a 3ph propane powered generator but it is expensive to run.
I plan to run the wire through a buried plastic conduit and have enough wire to be able to have two of each of the power carrying conducters and two ground conducters.
What will the current capacity be of this setup? (I realize it is probably not up to code)
stan
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stanley baer wrote:

Stan, with all due respect you are going about this the wrong way. You should first determine what load you need in your shop (a lot of guys get along fine with 60 amps) and make sure you can pull the required amperage off of your current panel (this would make the panel in your shop a "subpanel"). Once you have decided on your amperage and you know how far it has to run then go look up the voltage drop tables and find out what wire size you need. If that happens to be 8AWG then fine, use it. Otherwise just buy the wire you need. The expense will be trivial compared to the effort it will be to get power to your shop, and to the benefit (and value) you will get. And, it will be to code! Have you considered what would happen if there were a fire in your shop and your insurance company found a bunch of illegal wiring? Think one of today's insurance companies might try to weasel out of paying? I sure do! Do it right, do it once. Even if you can't use the 8AWG for pulling your subpanel, you may well be able to use it inside your shop when you wire all your outlets, etc.
Good on you for asking first!
GWE
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<snip>
If the fire were attributable to the incorrectly-installed wiring, then the insurance company would not be "weaseling"; it would be a legitimate denial of coverage.
Insurance companies are a business (like any other), they are not a charity. They owe it to their other paying customers, to their stockholders, and to their employees NOT to pay on bad claims.
- Michael
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Thanks for the information, I had not considered the insurance problem, but I don't want to do anything unsafe. Part of my reason for replacing the generator is that it is a bit of a fire hazard itself.
stan
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IIRC, 8 is good for about 40 amps, in free air. Bury it in conduit, the rating will go down. For a building that far away, you would probably be better off just running a separate service for the garage. By the time you purchase enough wire to run 200Ft with any appreciable load rating, you have probably invested enough to install a separate service at the garage.
--
Anthony

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To the best of my recollection, you can do 40 amps on 8 ga. cable. As Grant said, figure your voltage drop before going with that cable. I'll chime in that I'm a fan of "in code" electrical work, as well. Nothing inherently out of code in what you have said so far, provided stuff is buried to proper depth, conduit is properly sized, cable colours are ok for use (ground green, neutral white, hot lines red and black), breaker at feeder panel correctly sized etc. etc. Don't know about the US code, but it would be legal here to tape the exposed cable ends to address the colour issue.
Others will undoubtedly correct me with regards to US practise.
Adam Smith, Midland ON

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I bought the wire at an auction, three rolls, one black, one white and one green, so the colour was not a problem. Each roll weighs about 40 lb and I paid $30 canadian for all of it, quite a bit less than the scrap value. Six conducters of this size (about 1/4" dia each) should fit comfortably in a 1-1/2" conduit. I can't find anything in the Ontario code about doubling up the conductors, but otherwise I plan to stick to the code.
stan
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The current capacity of wire depends on the type of insulation. So you really have not provided quite enough information.
When you put in the conduit, be sure it is large enough that you can put in larger wire later if you need to. I would also put in a separate conduit for telephone, alarm signals, etc. If your shop is 200 feet from the house you will want a phone there and probably a fire and bugler alarm too.
I would also figure out how to feed power from the generator to the house for power outages.
Dan ( not going to look for my wire tables until I know what sort of insulation the wire has. )
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wrote:

And keep the data conduit at LEAST 3' away from the power conduit. I personally would go with 5-10' for that length of run. Which unfortunatly means another similar ditch. Ive seen far too many linear couplings because of data wiring being too close to power.
Unless..you use metallic conduit for the data run. Which then might..might might allow you to use the same ditch.
Gunner

"Considering the events of recent years, the world has a long way to go to regain its credibility and reputation with the US." unknown
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On Wed, 15 Jun 2005 09:38:16 -0500, stanley baer

Stan, The lowest rating for 8 gauge copper single wire is 60 amps. With 3 wires in a cable that drops to 40 amps. But, you should be using wire marked THWN, or THW. The W stands for wet. If wire is going underground, even in conduit, it needs to be rated for wet conditions. THWN wire in 8 gauge is rated at 50 amps for three wires in a cable at 86 degrees F. Voltage drop has to be considered. It needs to be less than 2%. For 8 gauge wire that's about 17 amps max @ 240 volts for 200 feet of wire. And with four 8 gauge wires the minimum conduit size for THW and THWN is 3/4. All the preceeding info is from the "Pocket Ref" written by Thomas J. Glover. Don't exceed these numbers if you don't know what you're doing. And, keeping the wiring to code is a good way to avoid electrocution and other hazards. I wouldn't wire it in a way that doesn't meet code. You shouldn't either. Nor should you trust the specs I listed without checking them out with a reliable source. ERS
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Thank-you for the detailed information Eric.
I plan to use 1-1/2' conduit and bury a phone line and water line, all 36" deep while I am at it. The writing on the wire is RW90 XLPE 1000V, which is moisture resistant as far as I can tell from a quick web search.
Does the 2% voltage drop current of 17A mean that I should fuse the sub-panel for 35A if I use 2 conductors? I was hopeing to get 50A. My high current loads are the welders which I operate at low duty cycles. since this is just a hobby shop there is never more than one big machine working at once.
stan
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stanley baer wrote:

You really would need 2 17 amp fuses[thoretically]
Voltage drop is the real enemy here, not max load.
The wire is the cheapest part of this equation, use the biggest you can.
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http://www.acehardwareoutlet.com/productaddonsdetails.asp?id008661&theSessionID b1089c928301dc74185ddd7de4bbe2&narrowmanu=&narFlag=0
An example: bulk 4 wire 1/0 UF at a buck a foot. 100 amp capacity, no conduit needed.
stanley baer wrote:

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On Wed, 15 Jun 2005 12:19:15 -0500, stanley baer

Stan, What the voltage drop means is that if you try to draw more than about 17 amps on one wire the voltage will drop more than 2%. Some electric things don't mind. But others do. Induction motors, e.g. the typical compressor motor, will draw more current as the voltage drops trying to speed back up. This extra current draw then lowers the voltage, which causes the motor to draw more current etc. This is how brown outs damage some motorized appliances. Your welder may not care if the voltage drops too much. You gotta book for the welder? It should say what it will tolerate. ERS
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stanley baer wrote:

It's against code to parallel conductors smaller than 1/0 AWG. 2002 NEC 310.4
Nate
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You could always run two circuits rather than one circuit with paralleled conductors. If I did that, I would run two 240 volt circuits and put the lighting on one of them. Trying to balance the 120 volt loads so there is not a lot of current in the neutral. That way if you pop the circuit breaker from a heavy tool load you won't be in the dark.
The voltage drop is something you can compensate for with a buck boost transformer. It is somewhat of a problem with loads that vary. I would use circuit breakers sized to protect the wiring and if you want to guard against low voltage use a panel in you shop with smaller breakers.
Dan
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stanley baer wrote:

Also, this wire insulation is not listed in any of the NEC tables for use as general wiring. A quick google search shows this cable is used for transmission/switchgear and some mining use.
Buy the correct cable for the job. Then you can size it for your needs.
Nate
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<snip>
It's a standard Canadian wire designation, suitable for use in wet locations. Most service entrance conductors here are RW90 insulated.
Ideally you could sell the single conductor #8 or trade it in for some larger cable. Unfortunately it's not a very useful or sought after item.
With the number of colors you have you'd be limited to 120 Volt circuits, unless you have lots of the black. It takes 4 conductors to do a standard 120/240 subfeed. Parallel runs in this gauge is not acceptable. The feeding breakers are not designed to hold 2 wires anyway. As others have pointed out the voltage drop at this distance will probably limit you to 15-20 amps total load at your shop with the #8.
For this application I would probably recommend #2 TECK breakered at 60 amps, or 1/0 ACWU. These are both armored direct bury cables. That should be enough to run a medium size welder and lights, etc. (again I've given Canadian cable designations)
Mike
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Forgive me if someone has already asked, but you have to know the type of insulation to properly answer the question. As already noted, voltage drop is also a consideration.
Vaughn
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The writing on the wire is RW90 XLPE 1000V which I understand to be moisture proof.
stan
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