Wire size for 250' distance to garage?

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I am thinking of running underground wiring out to the garage that is 250' from the elec. panel on the house.
My question is, what type and size wire to use?
My idea was a 220 line to a panel in the garage, where I could have 110 and 220 breakers.
Any ideas would be of help. Thanks, Cliff
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Depends on how heavy a load you're intending to support. If you're planning a fully-equipped shop with, say, a 3HP table saw, dust collection, a 5HP air compressor, and an arc welder, you'll need much heavier wire than if you just need a few outlets for a circular saw, a portable drill, and a radio.

Sounds like a good plan. 60A service should be more than adequate, unless you're planning on a LOT of high-load tools running at once. Normally, a 60A feeder would require a minimum wire size of 6AWG copper, but since it's 250 feet away from your panel, you'll want to bump that up to 4AWG.
Pull individual conductors through PVC conduit. (Make sure you use actual PVC electrical conduit -- "rigid non-metallic conduit" -- not PVC water pipe.) Minimum burial depth is 18 inches, as long as you're just going under your lawn or a residential driveway. If there's a street or alley in the way, 24 inches.
You'll need four type THWN conductors: two 4AWG hots (one black, one red is typical), one 4AWG neutral (white or gray), and one 8AWG minimum ground (green or bare). Code permits the grounding conductor to be downsized as far as 10AWG on a 60A circuit, but, again, due to the length of the circuit, bump it up at least one size.
Minimum conduit size according to Code is 1". Don't even think about it. Get *at*least* 1-1/2" if you want to be able to pull the wires easily. It will be easier to pull the wires one conduit section at a time as you lay the conduit, rather than trying to pull the whole 250' run at once. Pull boxes every 50' would be a good idea, too.
In the main panel, connect the two hot wires (red & black) to the poles of a 60A double-pole breaker, the neutral (white) to the neutral bus bar, and the ground (green or bare) to the ground bus bar.
In your panel at the garage, make sure that the neutral and ground bus bars are **NOT** connected to each other. They're required to be connected in the main panel, and required to be separate everywhere else. Connect the two hot conductors to the lugs on the main breaker, the neutral to the neutral bus bar (that's the one that's insulated from the panel), and the ground to the ground bus bar (that's the one that's *not* insulated from the panel).
--
Regards,
Doug Miller (alphageek at milmac dot com)
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On Wed, 18 Jul 2007 15:46:37 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

More useful information that is relevant to my current needs.
On a 150' total point to point run length would you say 6AWG would be ok.? Local utility not known for running low voltage, and my 120 circuits currently run the same distance to the back wall of the shop (where the new panel will be) are measuring about 117-117.5V (seems like they run a little higher in the winter).

Would you upsize to 1-1/2 conduit with 3-6AWG and a 10 ground?
My run is through attic space for the most part. No underground. At the point where the run will go from the house to the carport/shop complex, there is approximately 1-1/2' of distance. Considering weatherproof flexible for this transition. This to avoid tearing out the ceiling in a breeze way to run in that ceiling. Any flaws in this plan?
Thanks for all advice
Frank

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Yes, you're OK with 6AWG -- the voltage drop at 60A works out at about 3.6%, and anything under 5% is generally considered acceptable. At the OP's distance of 250' one way, though, he sees a voltage drop of 6% with 6AWG, and he needs 4AWG to get his voltage drop down to 3.8%. It wouldn't hurt for him to go to 3AWG, even, but it's probably not necessary.

No, but I'd go 1-1/4. Code minimum is 3/4 (!). My rule of thumb is to bump two trade sizes above the minimum: makes it *much* easier to pull the wires, and provides space for expansion as well, if you decide to upsize the circuit later, or add a few more.

In that case, I'd just use 6-3WG NM ("Romex") cable, and not bother with the conduit. If the attic is "accessible" (by stairs or permanent ladder), you'll need to install guard strips next to the cable for protection from damage wherever it's running across the top of the joists.

No, not really, except that you might have a couple of better alternatives.
Any chance you could fish an NM cable through that breezeway ceiling? Instead of using a fish tape, try Greenlee "Fish Stix" -- four-foot lengths of fiberglass rod with threaded connections at the ends, and various hooking and grabbing tools for catching hold of cables and wires. Great product. Wish I'd bought a set of those about twenty years ago. (They sell them at Lowe's, if you're interested -- around forty bucks, IIRC -- and I think I've seen something similar at HD, too.)
If not, consider that type NMC cable is approved for use in damp locations, and thus you could do the entire run with that. "Examples of such locations include partially protected locations under canopies, marquees, ROOFED OPEN PORCHES, and like locations..." [2005 NEC, Article 100, emphasis added]

No prob.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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wrote:

Wouldn't he be better of installing a 100 amp box instead of a 60 amp service, or even a 150 amp for possible growth later on?
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No, probably not. We're talking about a workshop here, not an entire house, after all. What in the world is he going to use 150A for?
The heaviest load that's likely to ever be seen in a one-person garage shop would look something like this: 3HP table saw (roughly 3kVA max) 5HP air compressor (roughly 5kVA max) 2HP dust collector (roughly 2kVA max) window air conditioner (say 15 or 16A at 120V, total about 2kVA max) maybe a kilowatt of lighting at 120V (1kVA) perhaps even a small refrigerator (1kVA)
Never mind any of the other tools he might have -- the table saw is the heaviest load, and the others won't be in use at the same time as the table saw. Total of the loads in simultaneous use is 14kVA = 58A @ 240V.
And that's assuming that he's ripping 12/4 sugar maple with all the lights on and the dust collector running, at the same time that the air compressor *and* the compressors in the window A/C *and* the refrigerator have both cycled on. Possible, I guess, but not too likely IMHO. *Far* more likely load is in the area of 30 to 40 amps at 240V most of the time.
--
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Doug Miller (alphageek at milmac dot com)
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Doug Miller wrote:

A high powered cyclone could have up to 5HP. That would bump up the max requirements a bit.
Relatively few people have that level of dust collection though.
Chris
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In the winter time he may have an electric heating system installed. -- Who knows what his plans in the future will be? That's what I suggested the 100 amp for. What's it going to cost him, perhaps 10 or 12 bucks more than a 60. He may even put a mercury light outside for security purposes.
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??? difference between 450' of #6 with 150' of #10 ground, and 450' of #3 with #8 ground is 10 or 12 bucks? where do you shop for your electrical? :~)
The panel is imaterial. Will probably be rated 100 or 125 amps because it will be more common and cost less and can still be used as a 60 amp. It's the wire that's big bucks.
Frank
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I wouldn't use a 125 amp box with a line that feeds 60A - it's asking for trouble, and is probably not code. that said, you could get away with it is you were REAL sure of the power being used.
shelly
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snipped-for-privacy@verizon.net wrote:
> I wouldn't use a 125 amp box with a line that feeds 60A - it's asking > for trouble, and is probably > not code.
I'm confused.
What is the problem?
It's done every day and does not violate code.
lew
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snipped-for-privacy@verizon.net wrote:

Asking for trouble in what way? Why would it not meet Code? There's no violation here -- I suppose you're concerned that the 125A panel could pull much more current than the feeder is rated for, but that can't happen if the feeder is properly installed with a 60A double-pole breaker at its source. If the feeder is simply taken off the main lugs, with no overcurrent protection at the source, then there certainly *is* both a Code violation and a serious hazard -- but the violation and hazard consist in having feeder conductors with no overcurrent protection, and are unrelated to the rating of the equipment at the other end of the feeder.
--
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Doug Miller (alphageek at milmac dot com)
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Dave wrote:

I suspect that over 250' the difference between #4 and #2 is going to be more than $10. Just in raw materials, #2 has 50% more copper than #4.
Chris
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Good point -- I hadn't considered the possibility of resistance heating. If he puts that in, then, yes, he definitedly needs more than 60A -- and he may *also* need to upgrade the service to his house.
--
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Doug Miller (alphageek at milmac dot com)
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One might argue that, but, this is it. I'll move before I expand again. One man shop. Residential subdivision restricted from commercial activity.
For seventeen years I've run it on one 30 amp branch feeder split to two 20's, one for fans and lighting, one for machines (120V), and one 20A 240V circuit with two receptacles. My little expansion will only add load (diversity factor considered) in that I'm installing dust collection which will run while any machine is running and some extra lights and fans.
Connected load will be much greater as I can bring some machines out of storage, however, in use load will not change much. I've load studied it and can't see ever getting over 45A, even If I invite a friend over to work with me. (done that before, never dimmed the lights).
And copper is expensive.
Frank

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Frank Boettcher wrote:
> And copper is expensive.
And so are line losses.
They are the hidden penalty you pay forever because you want to save a few $ at installation time.
Many of my contractor customers would size for minimum line drop using copper, then upgrade a size and use aluminum for feeders.
Terminate aluminum properly and you have no problems.
Don't terminate aluminum properly and you have BIG problems.
Lew
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On Wed, 18 Jul 2007 21:42:39 GMT, Lew Hodgett

Lew, I think you missed the point. This is a conversation about whether I install a properly sized 60 amp service to provide for what will normally be far less than 60 amp demand, or whether I bump up to 100 amp or 150 amp service to provide for what will normally be far less than 60 amp demand. Whether copper or aluminum, the overkill does not make sense.
Frank
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Frank Boettcher wrote:

2P-60AQ service will handle whatever a one man band can throw at it, unless of course you have a kiln or ceramic oven you are not telling us about<G>.
Lew
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Or electric resistance heat, as one fellow pointed out.
--
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Doug Miller (alphageek at milmac dot com)
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On Thu, 19 Jul 2007 11:35:31 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

Gentlemen, no Kiln's although I've lived close to the town that goes by that name. Resistance heat? this is Mississippi, I rarely use any heat. And I steadfastly refuse to put AC in, relying on natural ventilation, fans, and those lovely shade trees. When the summer sun finally does get an angle on the shop, in late afternoon, it is the signal to quit for the day. Don't want that dripping sweat to rust the machines or stain the wood. :~)
The 60 will do just fine.
Frank
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