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
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).
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
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.
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?
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.
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
I'm confused here. All that I've found is rated at 55 amps. It seems that regardless of the insulation rating on the individual conducters in the cable that might take it to 75 or 90C, the rating reverts back to 60C which is 55 amps for any #6 "romex" cable. Not sure what the logic is there or even if I understand it fully.
Not much chance, I think. Breezeway is flat roof or actually a one way minor slope with roof sheathing on top and ceiling sheathing below the rafters. There is a 12/2 wg in there that was the original light cable for the carport, however, It would be too much to expect to have those holes though the rafters be large enough for the larger cable. Got a right angle turn in there also.
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
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
??? 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
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
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
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.
Since there isn't any such thing as a 55A breaker, Code permits the conductors to be breakered at 60A. [2005 NEC, Articles 240.4 and 240.6, paraphrased]
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
Thanks. I didn't know that. That is the way I will go. Least cost and, since I am the labor, least amount of that in the attic.
Frank
You're welcome. General rule, any time there isn't a standard breaker corresponding to the rated ampacity of the wire or cable you're using, you're permitted to go up to the next standard breaker. The entire NEC is online here at the URL below; consult Article 240.4(B) if you want all the gory details. Article 240.6(A) lists the standard ratings.
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.
Lew
BTW, forgot to ask.
Any chance you have access to the termination equipment for aluminum conductors (rent, barter, whatever)?
If so, #4 AWG aluminum should be very attractive.
Lew
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