Circuit Size Question

I'm trying to decide what size circuits I should run in my new basement (unfinished) shop. I just purchased a 3hp (18amp) table saw and a 2hp (12 amp) dust collector from Grizzly that both run on 220v. I plan to split these out to 2 separate 20 amp circuits. I have a couple of questions:
1. Should I install GFCI outlets or breakers on either/both of these circuits?
2. Could I get by with a single 30 amp circuit?
3. I have plenty of room in my main panel but should I run a subpanel for these circuits and future upgrades (florescent lights, more 110's) anyway? Why?
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You're better off using a 30A circuit for the table saw. It may even be necessary; check the owner's manual for the saw's electrical requirements.

Code requires ground-fault protection on 120V outlets in basements, but AFAIK it's optional for 240V circuits. It's not a bad idea anyway, though.

No. It's never a good idea to load a circuit at 100% of its rated capacity (and it's a Code violation). You need two circuits.

Yes -- but the lighting circuit(s) should be supplied from your main panel, not from the subpanel.

a) Provides a single point for disconnecting power to all receptacles in the shop in case of emergency (or to prevent kids from starting up power tools). Lighting should be supplied from the main panel so that an overload on the subpanel doesn't leave you in the dark.
b) Easier and cheaper to install new circuits in the shop: you don't have to pull as much wire as far, if your starting point is already in the shop.
-- Doug Miller (alphageek at milmac dot com)
How come we choose from just two people to run for president and 50 for Miss America?
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I'm far from being an expert and will read closely other more expert opinions but lets see if I'm on the right track here or not.
C.Poole wrote:

I'd use just a breaker on seperate circuits w/ a subpanel.

You could however you may overload it if both tools are running at the same time. Someone else may be in the shop with you doing their thing.

Since its unfinished, I'd run a sub panel. That way if you ever need to power down everything in that area you can do so closeby and quickly. Plus it lets you run numerous circuits for the shop, again all controlled at one place, the sub panel.
I've a 12x16 external shop I ran a subpanel to. The 16' walls have 4 outlets each on their own 20a circuits. The 12' wall has 3 outlets on its own 20a circuit. The 6 overhead 4' florescent fixtures have their own circuit, 15a. I've a small pond w/ pump that I'll plug in this summer and will add a GFI plug for it since its going outside the shop, plus I might plug in other stuff outside - who knows. In my case there will rarely be anyone else in there at the same time as I, however...
Bottom line I think everyone would agree with is, if its unfinished, now is the time to plan for the future, plus 20%. You'll never have too much power nor too many outlets so give yourself some room for expansion later on while you can w/o tearing up the place.
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GfI would not hurt but is prop. not a necessart, seperate circuits, the table saw could draw too much at start up. and close accessible panels are always handy.
C.Poole wrote:

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"C.Poole" writes:

Since you have lots of spaces in that panel, let me suggest the following:
Buy a full box of 10-3 /W/ ground Romex and use 2P-30A c'bkrs for all your 240V circuits. (Leave the neutral unconnected at the receptacle if necessary)
Run individual circuits for each tool.
Buy a full box of 12-2 /W/ ground Romex and use 1P-20A c'bkrs for all your 120V circuits.
You save money on wire because you are buying full spools and the c'bkrs are all the same price 60A and below with the obvious difference between 1P & 2P.
Can't use Romex? Then buy 500 ft spools of single strand and do the same job.
HTH
And yes, spent a few years in the electrical distribution business, designing systems and selling equipment.
--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
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I plan to use Romex- that's what the rest of my house is wired with, but under what circumstances would I NOT be able to use Romex or a similar style cable?

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One instance would be that some local codes frown on using romex in conduit, and you may have to de-rate the ampacity of the circuit if you do use it in conduit.
However, the NEC makes a good case for protecting romex with conduit in a hazardous environment (a shop should qualify), so it is one of those issues where there may be no clear cut guidance and you have to go with how the inspector feels that day.
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Swingman thus spake:

In my neck of the woods, non-metallic sheathed cable HAS to be installed either in an enclosed wall, or in conduit. It absolutely *cannot* be installed on the surface of a garage wall or in an exposed stud wall in a garage. I would (and did) go with THNN wire in surface mounted conduit - easy to change, exactly to code. GFCIs are required on all 110v branches, but not on 240s.
FWIW,
Greg G.
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Been through this too many times ... it is specifically why I mentioned it as an area to be aware of in answer to the question:
"I plan to use Romex- that's what the rest of my house is wired with, but under what circumstances would I NOT be able to use Romex or a similar style cable?"
Romex in conduit is OK in this locale as long as it is protection for the wiring, but NOT as a wiring system.
You gotta be aware of, and be careful with, the terminology that inspectors will often use for "gotacha's" on a bad day.
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Since all Romex since the late 80s has been 90c for derating that is not an issue. I can't imagine what their justification for derating would be anyway or what table they would use. The derating table is the same whether a group of conductors is in a cable, a raceway or simply bundled together. In places that don't allow cousin Billy Bob to make up the rules as they go it is recognized that you can sleeve Romex in conduit for physical protection. Usually that is required on unfinished walls up to 6'6" off the finished floor.
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"Greg" wrote in message

Generally based on percentage of conduit fill, with romex considered as a single conductor for calculating same, EXCEPT in cases where the conduit is used to protect exposed wiring.
I mentioned the issue SPECIFICALLY because it IS an issue that is not clearcut and comes up all the time, so being on the lookout for it in shop wiring plans is wise if you're doing the work yourself and having it inspected, as the OP apparently is.
Pretty difficult to say it more clearly than that.

That's what I stated, which you left out. However, you can just about bet that romex in conduit is non-code as a "wiring system" in _most_ parts of the USofA. It certainly is my area.
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"C.Poole" writes:

Primary limitation of Romex is that it can not be run exposed. It has to be run behind a wall as an example.
What you are and are not allowed to do is under control of local codes in most situations.
If you are going to have exposed studs in the garage, then it is conduit or BX time.
Same would apply to surface mounting over existing plaster board.
If you are going to cover the wall studs with plaster board after wiring, then romex works.
HTH
--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
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You have to add "where exposed to physical damage". When I was in Md it was very common to see Romex on running boards in garages and basements. My area of Florida intreprets that as exposed to physical damage if it is within 6'6" of the floor.
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"C.Poole" > wrote in message

You're wise putting them on separate circuits. Use 10ga wire for both in case you want/need to upgrade later.
Is the saw rated at 18amp at 120v? ... if so, 20A should be sufficient if your're going to run it at 220v,.
However, if the 18A rating is at 220v for the saw, you need to go with 30A for the table saw.
... if you run 10ga wire, you got it covered no matter what..
May want to make the Dust Collector 30 A from the get go in case you want to upgrade it in the future.

Most codes don't require GFCI on "dedicated circuits" for a single tool, but if your basement is damp, strongly consider it.

The DC has to run while other tools are on, so it is much better of on its own.

You may have plenty of room now, but things have a habit of filling up quickly for a shop. A subpanel is nice to have, and safer cause you can cut everything off in the shop with one switch, or two, for any number of reasons. ... 60A Main Brkr in the subpanel and a 60 amp Brkr feeding the subpanel from the main is what I've got ... works nicely.
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Some thoughts:
You can never have enough circuits (it's kind of like clamps).
Make sure your machinery and your lighting are on separate circuits. You will discover the wisdom of this the first time you trip a breaker and you find yourself in a pitch-black room standing 2 feet away from a 3 HP saw blade that's slowly spinning down.
Putting the everything (except the lighting) on a sub-panel makes it easy to power down the whole shop. A disconnect switch upstream of the panel that you can padlock in the "off" position can give peace of mind if you've got kids in the house.
Add up how much stuff you might have running at one time. The obvious things are the 3HP saw and the 2HP DC. Right there that's 25 amps or so (at 220). But, what else? What's the heat like in the basement in the winter? Maybe one or more 1000/1500W electric heaters? Maybe a dehumidifier or air-conditioner in the summer? In addition to the DC, maybe a room air circulating dust filter?
You'll have your basic lighting on another circuit, but if you're like me, you'll also have random additional task lighting plugged into utility outlets. An air compressor? Tons of little stuff like fans, radio, recharger for your cordless drill. I couldn't survive without my electric pencil sharpener :-)
It all adds up. 30A @ 220V isn't sounding very big any more, is it?
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On Fri, 19 Dec 2003 21:32:45 GMT, "C.Poole"

220 v. GFCI's are very expensive (over $100 ea). I did not install these in my shop. However, I did use them on each 120v circuit.

That should be plenty to run a total of 7 HP.

I would not install one, if the main is conveniently located and has available room for expansion. I installed all my outlets at once (and lots of them) because it made it much easier. Install more receptacles than you think you will need. They install fast, cheap, and easy once you get going. "Leap-frog" the circuit outlets for more overload protection.
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The saw is a potential problem, depending on how you intend to wire it up. If you're running permanent wiring to it -- as opposed to a socket that you plug a cord into -- you're limite to 80% of the rated circuit capacity for the 'permanently connected' device. that's 16A load allowed, for a 20A breaker.

*PROBABLY* not required, though some jurisdictions _are_ moving toward requiring GFCI protection in garage/basement areas where there is a "possibility" of water accumulating.
There is no 'downside' (other than materials cost) to doing so, however.

Requires #10 wire, _and_ 30A-rated outlets _and_ mating plugs.
Can't permanently wire 18+12A worth of devices on a single 30 A circuit, due to the 80% restriction mentioned above.

Authoritative answer: "it depends"
On how big the space is, how much you expect to grow the number of tools, etc. My "shop" survives on a _single_ 15A circuit. of course, it's the 'back bedroom' of a 2BR *condo*, with about 50(!!) sq ft of 'usable' space, and -never- more than a single tool running at a time.
One argument in favor of running a sub-panel, which you hang all the 'dangerous' tooling off of -- running lights *separately* from the main panel -- is that you can kill, and/or "lock out" all the dangerous stuff with a single master kill-switch at the sub-panel. A padlocked disconnect, and you don't have to worry about kids getting into trouble when nobody's around to supervise.
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