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Old 12-17-2008, 10:23 PM   #76
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electricity 750 ft away!?


Would you trust unsupervised kids around Electric outlets in a treehouse, which does not qualify as a safe structure to begin with. If I was the OP, I would ditch the whole idea, and as someone else stated, give them some boards & nails. Worst thing is also, if one of their friends fell from it, the person that built it would be liable, and no amount of Insurance, or lawyer would save them from what would happen in the courts.

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Old 12-17-2008, 10:24 PM   #77
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electricity 750 ft away!?


I'm afraid that all of this tech talk, and the comment about parenting has scared the OP away. He's likely to be going to Home Depot to get his answers<g>
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Old 12-17-2008, 10:24 PM   #78
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The drop as the calculator that I used, for a 120volt/20amp circuit is 2/0 for Copper wiring, 4/0 for Aluminum at a 750' run.
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Old 12-17-2008, 10:37 PM   #79
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electricity 750 ft away!?


Quote:
Originally Posted by gregzoll View Post
The drop as the calculator that I used, for a 120volt/20amp circuit is 2/0 for Copper wiring, 4/0 for Aluminum at a 750' run.
Unless the kids will be running a large table saw(insert warning siren here because THAT would be really dangerous), I don't think you need to base the voltage drop on a 20A load. Also, I believe on a MWBC, voltage drop is calculated using the 240V single phase calculations.

Last edited by jerryh3; 12-17-2008 at 10:47 PM.
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Old 12-18-2008, 06:39 AM   #80
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electricity 750 ft away!?


Originally Posted by Silk
meaning that each "hot" shall be connected to the neutral, otherwise it wouldn't be part of the circuit, right?



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Originally Posted by KE2KB View Post
I don't think so. A typo on your part, right?

Not really, I was more thinking out loud.

Branch Circuit, Multiwire. A branch circuit that consists of two or more ungrounded conductors that have a voltage between them, and a grounded conductor that has equal voltage between it and each ungrounded conductor of the circuit and that is connected to the neutral or grounded conductor of the system.

If the branch circuit consists of 2 "hots" and a neutral. Once you remove the neutral from the equation, it doesn't fall under the "classic" definition of a multiwire branch circuit anymore. You are bastardizing the circuit, but yes, you are right, it is still a MWBC as long as we allow the exceptions. Although I would contend that the 240V rec. is fed from a MWBC, but that is a matter of semantics and doesn't fall neatly into the NEC anywhere as it is not a feeder.

Now there is nothing against code with wiring a 240 volt rec. off of this MWBC, but it defeats the intent of the circuit. The intent was to "share a neutral" and make the wiring cheaper, with the added benefit of less voltage drop if the loads on both legs are somewhat balanced.

I have never wired a MWBC, or run across one somebody else wired, that included a 240 volt rec., and I can't think of a reason why I would. I'm sure someone has, otherwise the NEC wouldn't have the exceptions to include it. I would be interested to hear for what application.

But back to the original point, is it a 120/240 volt circuit and need to be buried 2 feet down (if it's not in conduit).

I believe the circuit is a 120 volt circuit if it is wired as a 120 volt circuit, and my inspector agrees since he has passed such installations in the past, but maybe other inspectors wouldn't.

I guess the answer would be that if you want to dig by hand, ask the inspector if 1 foot is acceptable. If you are trenching anyways, go with the 2 feet and don't worry about it.

P.S. Just to stop any future posts about "all services are 3 wire, 120/240", they are not branch circuits and don't apply. Sorry, but I just seen it coming.
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Old 12-18-2008, 08:07 AM   #81
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electricity 750 ft away!?


Even with 240v in the calculation, it would have to be ran with 3/0 Copper. There is no way around the fact that the OP has a Pipe Dream.
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Old 12-18-2008, 08:37 AM   #82
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electricity 750 ft away!?


Quote:
Originally Posted by gregzoll View Post
Even with 240v in the calculation, it would have to be ran with 3/0 Copper. There is no way around the fact that the OP has a Pipe Dream.
Gregzoll, he's not running the full capacity of the circuit at the far end, its mainly for lighting as has already been stated on here before. There is no reason to run that big of a wire, not to mention it would never fit on a 20 amp breaker. I think the Op would be fine with anything between 10 gauge and no larger than 8 or 6 gauge wire (even #6 is big for this project). Lights will work plenty fine with any amount of voltage drop, they will just be a little bit dim at the end that's all (of course im reffering to incandescent lights).
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Old 12-18-2008, 09:28 AM   #83
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electricity 750 ft away!?


OK. Here it is.

210.19 Conductors - Minimum Ampacity and Size.
(A) Branch Circuits Not More Than 600 Volts.
(1) General. Branch-circuit conductors shall have an ampacity
not less than the maximum load to be served. Where
a branch circuit supplies continuous loads or any combination
of contiquous and noncontinuous loads, the minimum
branch-circuit conductor size, before the application of any
adjustment or correction factors, shall have an allowable
ampacity not less than the noncontinuous load plus
125 percent of the continuous load.

FPN No.4: Conductors for branch circuits as defined in
Article 100, sized to prevent a voltage drop exceeding
3 percent at the farthest outlet of power: heating, and lighting
loads, or combinations of such loads, and where the
maximum total voltage drop on both feeders and branch
circuits to the farthest outlet does not exceed 5 percent,
provide reasonable efficiency of operation. See FPN No.2
of 215.2(A)(3) for voltage drop on feeder conductors.
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Old 12-18-2008, 10:39 AM   #84
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electricity 750 ft away!?


Quote:
Originally Posted by gregzoll View Post
Even with 240v in the calculation, it would have to be ran with 3/0 Copper. There is no way around the fact that the OP has a Pipe Dream.
What calculator are you using? Are you using 20A as the load?
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Old 12-18-2008, 01:56 PM   #85
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electricity 750 ft away!?


http://www.elec-toolbox.com/calculators/voltdrop.htm As for the 240volt, that was 60 amp to get the 3/0 wire size.
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Old 12-18-2008, 02:26 PM   #86
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electricity 750 ft away!?


With 3% drop (3.6v), 400w at 120v = ~3.3A, gives 1.1 Ω total wire resistance.

1500' loop distance would need <0.73 mΩ/ft. Using copper at 20C, #9 AWG doesn't quite do it so you'd need #8 AWG.

Heating in this wire due to the 3A would be ≈ +0.2C above ambient. Power loss in the wire ≈ 12w.

Last edited by Yoyizit; 12-18-2008 at 02:29 PM.
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Old 12-18-2008, 02:33 PM   #87
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electricity 750 ft away!?


you guys know me.... i like simple and cheap! go to your local bigbox store and buy a $50.00 'battery jumper' that recharges in the house. it's capable of running anything 12v dc via 2 cigarette lighter openings in the front. we ran a small tv and a laptop at the campsite.......... i used one for the kid's bus stop at the end of the driveway with 2 nails wired to the wood and just clamped the red to one, the black to the other to light it up! ran decorations 12v for holidays too there the same way. all your sons have to do is remember to bring it back to charge! (we watched tv for over 8 hours on a full charge) simple and cheap.... you guys know me.

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Old 12-18-2008, 03:31 PM   #88
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67# per 100 Ah. You could leave the battery on the ground and run cables up the tree.
You'll need deep-cycle batteries.

No safety problem with 12v but if you short anything your cable insulation will instantly become brittle and have the texture of toast, and your copper will lose its shine.

You'll need a small cart to carry three of these batteries that distance, unless your name is Ahhhnold.

Don't let your clothes touch the batteries or they will get small holes after a month or so (or quicker), and open cuts on your hands will sting.
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Old 12-18-2008, 03:53 PM   #89
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I suppose this:
http://www.amazon.com/Coleman-Rugged...ef=pd_sim_sg_1

is too simple but as near as I can tell one or two will put out as much light (for $20-$40) as the hard wire will (for $1000). Plus the kids could use them on their walk back from the treehouse.
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Old 12-19-2008, 05:23 AM   #90
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electricity 750 ft away!?


Quote:
FPN No.4: Conductors for branch circuits as defined in Article 100, sized to prevent a voltage drop exceeding 3 percent
FPN for voltage drop is just a recommendation KB2KB... and yeah if this were something more serious than a treehouse you might want to size the conductors up... but if it were me, I think I'd use 8 or 10 gauge.

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