Which wire for pole barn?

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Old 11-10-14, 11:23 AM
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Which wire for pole barn?

We're getting ready to bury cable to run power to our pole barn. Planning to provide 60amp service, and it's about a 115ft run to the panel. Using a calculator I googled, it looks like that means at least 4AWG copper or 3AWG aluminum. Planning to direct bury. So, what wire do I need from Home Depot? I found this one: Southwire 1000 ft. 2/1 Stranded 3E Aluminum USE Wire - Black-27282301 at The Home Depot

But, I don't know if running a bunch of individual strands is ok or a bad idea. I also found this one: Southwire 500 ft. 2-2-2-4 AL USE MHF Service Entry Electrical Cable-28712801 at The Home Depot

But, it costs a bunch more. More $ is ok if there is a good reason.

Bonus question: I've read that the barn should have its own ground rather than running back to the house ground, true?
 
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Old 11-10-14, 12:10 PM
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Either individual USE wires or a cable assembly would be allowed; price per foot will be very close. I recommend the 2-2-2-4 MHF cable for your direct burial to the barn. Depth should be 24" minimum, with PVC conduit sleeves going in and coming out of the ground. Is the main panel of the house which will power this feeder on an exterior wall?

You don't really want to use the minimum size cable because of the distance. At over 100' jumping up a size will help to reduce severity of voltage drop in the barn.

It is a good idea for the barn to have a separate ground wire (4 total wires in feeder) for added safety. If there are other conductive pathways (phone, cable, water, ...) between the house and barn, the separate ground wire is mandatory. Ground rods are required at the barn in either case.
 
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Old 11-11-14, 07:11 AM
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Hey, thanks for the quick response!

- The main panel is on an exterior wall, BUT I am hoping to run the cable partially inside to avoid trenching through my septic tank/drain field. For the interior run I understand I can't just staple the MHF under the joists, and would need to run in conduit or do a junction box - is that right?
- Agree I don't want to go minimum sizing, so I think doing 2-2-2-4 is jumping up a size if I understand correctly.
- I am planning to run cat6 (shielded) along with this wire so it sounds like the separate ground will be required. Will I connect the barn panel to both the barn ground and the ground running back to the house?

Finally, for some bonus complexity, I am considering moving my generator inlet from the unsheltered side of the house to the shelter of the barn. I have a legit interlock installed on the main panel with a 50amp breaker. Would this same 2-2-2-4 MHF be appropriate for a generator inlet in the barn, feeding back to the 50amp interlock on the main panel? If so is there any issue running them in the same trench/conduit?

Thanks again!
 
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Old 11-11-14, 08:22 AM
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I am planning to run cat6 (shielded) along with this wire...
You may not run data/communication cables in the same conduit as power. Ideally you would want to keep a one foot (or more) separation between communications and power wiring. Understand that you will have to use a cable that is listed for either direct burial or for use in wet spaces (outside/underground conduit). You also need to remember that Ethernet is limited to 100 meters or a bit more than 300 feet between points of signal boost such as a router.

Power from the generator to an approved interlocked panel may be run in the same trench as the other power but IF you run it in the same conduit you might have to derate.

Yes, the panel in the barn does need to be connected to both the grounding electrode (ground rod) at the barn as well as the equipment grounding conductor from the house.
 
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Old 11-11-14, 11:01 AM
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I recommend the 2-2-2-4 MHF cable for your direct burial to the barn.
I would also recommend the mobile home feeder.

I understand I can't just staple the MHF under the joists, and would need to run in conduit or do a junction box - is that right?
That's right, it cannot be stapled to bottom of joists although I've seen it done that way. In fact, it cannot be run inside the home even in conduit and must be transitioned to another wiring type before entering the house. I recommend transitioning to 6-3 NM-B cable at a J-box on the house.
 
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Old 11-12-14, 01:56 PM
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Thanks again all. Another option I have is burying all the way to where the panel is on the outside wall of the house, but I would have to go past the sewer line to the septic tank. If the sewer line is at least 24" down can I go over it? Or do I have to go under it? Still direct bury or is conduit now required?
 
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Old 11-12-14, 07:19 PM
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If the sewer line is at least 24" down can I go over it? Or do I have to go under it? Still direct bury or is conduit now required?
Direct buried cable needs 24 inches of cover and conduit needs 18 inches of cover.
 
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Old 11-13-14, 09:52 AM
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My recommendation would be to go underground the whole way and hand-dig at least 12" under the sewer line. You could do a transition to 6-3 at the house wall; however a copper to aluminum joint is difficult for a novice to get right. It's possible but the connectors are expensive and some technique is involved. When possible I prefer to have no splices in feeder lines as it complicates the installation and adds a potential point of failure as well as added expense in fittings, a big j-box, Polaris connectors, etc.
 
 

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