Direct bury vs conduit for electrical cable

I'm running some electrical cable from one buildeing to another and I need to go underground for about 30 feet. I'm going to run 3 lines of 12/2, unless there's something better, but I'm not sure how best to run it. I laied some conduit for some Cat5 cables that I needed to span the same section, because I figured I might be adding additional lines in the future and wanted easy access. I don't think I'll have the same requirements for the electrical, and I've heard that I don't want to run the electrical in with the Cat5 becuase of interference. I've already purchsed the UF cable, didn't notice it at the time I bought it, but I've got it now. So, my question is, should I direct bury the cable or run it through some conduit. I don't have money to burn, but I want to do this correctly. Just for reference, I live in rural central Illinois, if that makes any difference.
Thanks, Nate Baxley
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You shouldn't run the electric in the same conduit as the other cables. More for safety if not for interferance.
If you going to run the electric in the same trench, you should have it 2 ft lower than the other utilities. If you can't do that, then you should dig another trench seperated by a couple feet..
Different codes in different areas will say something similar to this..
I live in a rural area but the county has requirements similar to this.
In years past, we got away with a lot of things that we shouldn't even consider today. So many utilities are going underground it is becoming even more important to conform to a uniform standard, if not a local code.
All for the better. I feel more secure around my place in the woods, knowing that all of my utilities are underground and I can run around with the backhoe or crane and not have to worry about snagging a wire.. If I'm in doubt about an underground, it's just a matter of a phone call and the utilities guys are here in a flash to do a 'locate'..
Steve
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In my area, Columbus, Ohio, you must bury 18" deep when not using a ground fault circuit breaker and 12" when using one. UF wire is meant to be buried directly, the soil absorbs heat from the conductors, so that you don't have a insulation melt-down. If you wanted to run conduit, you would use single conductors of stranded wire appropiate to the amperage of the intended load. Hope this helps. Wayne

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Hi Nate,
As the others have said - you need to bury the wire seperately - and 1.5 - 2' deep (some codes require a treated board placed over the wire & the wire laid in sand) - best to check with your local municipal office.
I'm taking it this is a garage you are running the wire to? Have you considered running a larger 3 wire conductor and having a subpanel at the garage end? e.g. a 8-3 conductor from a 40 AMP dual pole breaker going to a 8 or 16 slot sub-panel. This will be more expensive - but give you room to expand.
That would allow you to add additional 14-2 circuits in the garage at a later time - and allow for 220Volt devices like a welder. If you go that route - you might be able to return the 12-2 wire - or - sell it.

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And this is how you must do it if you're going to do what I think you want to do. A separate building must have only one source of power -- a single branch circuit, a multiwire branch circuit, or a feeder. With 12-2 cables to pick from, you can't have more than 20A @ 120V in that building. You'll have to run either a 12-3 multiwire circuit, or a 10-3, 8-3,... feeder to a subpanel. You can use the 12-2 UF for your branch circuits inside the building if you want to, although it is a pain to work with compared to plain NM cable. I'd recommend 8-3 UF as the minimum starting point for a building, and 6-3 would be better unless its is really small (but its easy for me to spend your money!)
The NEC advises to keep low voltage cables at least 2" away from power cables. However, there is an exception for the power wires in a raceway or in cable (like NM or UF). Personally, I'd try to keep the cat5 at least 6" away from the power wires and I'd put them in their own conduit perhaps with a CATV cable.
-- Mark Kent, WA
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Ok, this is a garage, and the idea of being able to expand it later is appealing. If I want to run 8-3 from my current breaker box, what do I need to do? You mentioned a 40 AMP dual pole breaker, I've only dabbled with my breaker box a little, would a dual pole breaker be one that takes up two spots on the box? Will it have 3 spots for wires? If not, where do I connect each of the 3 wires? So, I add one of those and run 8-3 wire from there to the building and once I'm there install a breaker box there. Is it obvious where to connect the 3 wires there? Will I have a second grounding pole? Once I have that box, I guess that I can run as many new lines off there as I need?
Sorry for all the questions. I'd appreciate any suggestions. Thanks, Nate Baxley
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I'd search the archives of this group for posts containing the word subpanel and you should figure out what to do. If you've never worked inside the panelboard before, you may want to get someone who has to help you. A double pole breaker looks like two single breakers side-by-side with a bar connecting the handles on each breaker (and they take two slots). There are two holes in the breaker and the red wire goes in one and the black in the other. The white goes to the neutral bus and the bare ground goes to the ground bus (which may actually be the same bus bar in the main panel or maybe not).
At the garage, you can only have 6 circuit breakers or else you need to buy a panel with a main breaker. So think about what you want. The red and black go to the main bus connections or main breaker. The white goes to the neutral bar. You'll probably have to buy a separate grounding bar and bolt it into the panel. Put your bare ground wire on this bus. It is important that the neutral bar in the garage panel not be electrically connected to the panel chassis, only the ground bar may do that. There is usually a green bonding screw that connects the neutral to the chassis. DO NOT install this screw.
You must also ground detached structures. You'll need two grounding rods and I'd run a length of #4 copper from the panel ground bus to the first rod, through an acorn clamp, and then to the second rod terminating in an acorn clamp. These rods must be at least 6 feet apart and 6 feet from any other ground electrode. You also could use #8 wire for your ground rods, but then you'll have to protect that ground electrode wire from physical damage. With #4, you can just run it down the wall and not worry about protecting it.
Finally, if you're going to all this trouble, I'd run 6-3 wire w/ground. It seems like the NEC wants you to run a 60A feeder to a building, but the code says the disconnect must be rated at 60 amps (doesn't say what the feeder ampacity must be).
-- Mark Kent, WA
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> I'm running some electrical cable from one buildeing to another and I > need to go underground for about 30 feet. I'm going to run 3 lines of > 12/2, unless there's something better, but I'm not sure how best to > run it. I laied some conduit for some Cat5 cables that I needed to > span the same section, because I figured I might be adding additional > lines in the future and wanted easy access. I don't think I'll have > the same requirements for the electrical, and I've heard that I don't > want to run the electrical in with the Cat5 becuase of interference. I've already purchsed the UF cable, didn't notice it at the time I > bought it, but I've got it now. So, my question is, should I direct > bury the cable or run it through some conduit. I don't have money to > burn, but I want to do this correctly. Just for reference, I live in > rural central Illinois, if that makes any difference. > > Thanks, > Nate Baxley
Nate If you want a job that complies with the US NEC you can not run multiple branch circuits to an outbuilding. In other words your electric supply should be in a single branch circuit or feeder unless you run emergency power, or you have two or more types of power with different voltage characteristics which is very rare in homes.
The code requires that each building be supplied by only one feeder or branch circuit and that there be a disconnecting means for each building. If you run only one branch circuit the disconnecting means can take the form of a snap (toggle) switch or set of snap switches. The set of snap switches is three or four way switching rather than multiple single pole switches on separate branch circuits. If your loads can be served by two circuits then you can run a multiwire branch circuit and use a double pole snap switch as the disconnecting means. If you have a separate emergency power panel then you can run a third circuit from that to get the three you want.
If you do install more than one branch circuit you need to build a grounding electrode system for the outbuilding. That system will consist of a minimum of two driven rods if there are no other grounding electrodes such as a concrete encased electrode. The Grounding Electrode System will have to be connected to the Equipment Grounding Conductor (EGC) that is run with the circuits supplying the outbuilding.
If you want to allow for future change of use and loads then you will run an 1&1/2" nonmetallic conduit between the house and the garage. Install a six slot sub panel; minimum; in the garage, Install a back fed double pole breaker that is fitted with a tie down kit in the garage panel to use as the required building disconnecting means. Install a separate Equipment Grounding buss bar in that panel. Remove the bonding screw or strap that connects the insulated neutral buss to the garage panel's cabinet. Run the Grounding Electrode Conductor from the grounding electrode system of the garage to the equipment grounding buss of the garage panel. You now have breaker slots to supply your three branch circuits and you still have one open slot for a future 120 volt load. If you want to allow for 240 volt loads then you will want to install an eight or more slot panel so you will have more spare slots.
The supply to your garage sub panel will take the form of a three wire plus ground feeder that you will size to carry your present loads and leave some ampacity for additional loads.
I hope this answers your question. If you need more information just ask.
--
Tom







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Thanks for the great info Tom. Now I just have to get up the ambition to do all of that. It certainly sounds like more work than running three lines but would probably be a better solution in the long run.
Nate

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