I am wiring a woodworking shop in my attached garage.
I need about 12 120V outlet boxes plus 5 240V boxes –
about 4 20A circuits plus 4 240V dual 20V circuits.
I have 240V 2 HP DC, 3 HP planer, and will convert my 1 HP TS to 240V.
I work alone, so I think the overall plan is pretty reasonable (right?).
The sub panel will be near the main basement panel.
The space above the garage ceiling is just rafters.
(I am ignoring the lighting circuit in this positing)
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Now to the areas that really confuse me…
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I have quite a bit of 2 & 3 wire 10 guage cable.
But I suspect I should be installing conduit and fishing wires. In general terms…
Am I correct that conduit is preferable?
Is metal conduit preferable to PVC?
Is 12g wire OK or should I use 10g?
Is it preferable to make the runs up high near the ceiling with drops and junctions at the corners (or are pre-formed 90 degree bends better?)
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Obviously I really am confused…
Replies
Conduit is usually for industrial applications, or for situations where you need to protect the wire. If this is your home, I can't imagine the need to do it this way as it will just drive up the cost and provide no practical benefit. When you say 2 and 3 wire cable, is that plus ground, or total # of conductors? I assume your referring to Romex, that is in a common plastic sheath. For the amperage your running the 12 gauge is fine.
Are you pulling a permit for all this? If so, your local code will guide you in what can and can't be done.
You really ought to hire an electrician to do the work if you want to make certain it is all done properly.
The next best thing would be to search around for an electrician who is willing to "consult" with you off the books on a cash basis. Retired guys who are no longer active in the trade are ideal for this purpose; for a $100 bill, they would come around and help you get every thing set up correctly, and once the work is done, take another $100 to make sure you got it right.
What you're doing is pretty simple, and spending $200 for a private tutorial is cheap insurance to make sure you don't burn your house down.
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"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
I was not planning on pulling a permit. But I don't think there's anything very complicated here, as long as I understand the importance of grounding. I making the effort to be more professional than I often have in the past. My concern is if I am being a dope to save the $300-$400 by not running some type of conduit.I hoped this forum would provide some practical (vs. "PC" or "official") advice.I am 60 and I am used to getting my hands dirty, despite being Harvard 1957. In the past, I've added circuits, modified circuits, run underground circuits to my sheds, etc. In a former life, I was the wiring expert in my car repair business - LOTS of differences, but also LOTS of similarity.I have sufficient Romex (3-wire plus ground) on hand to do this job - which I had already started to run. I already have a panel. I already have sufficient receptacles, switches, and boxes (mostly plastic but some metal). I have circuit testers, a wire "fishing" tool, tons of wire caps, etc. SIDE NOTES:
<=> Garage sales are wonderful - I got a new sub panel with a dozen new circuit breakers for $5 and a used industrial panel free with enough feed wire to reach my main panel (& thick enough for about 400A).
<=> Ironically, I actually gave two large boxes filled with flex conduit/metal boxes/connects/etc. to my local electrical wholesaler when I was cleaning out my basement - my thought was "I'll never use this")
Well GD, I'll tell ya.
I ain't quite 60, but gettin close. I too like getting my hands slightly soiled. I wired my own shop last summer. The walls were open and I could have very easily run Romex and been done with it. But I'm a bit retentive about certain things and decided to run all the runs from the panel to the various light and outlet boxes in Conduit (metal). I only used 1/2 inch conduit and maybe should have used 3/4 but what the heck.
The reasoning for me was simple. If I wanted to upgrade from 12 to 10 guage someday for a specific outlet set, pull the 12 guage, insert some 10, and done! Now, I kinda like working with conduit. It's sort of like playing with the old erector sets when I was kid. Besides, it's artistic at times.
What I found when I had the inspector out for the electrical was that he was so impressed, he didn't question a darn thing. Just looked at it, shook his head, smiled, and said something like "Don't need to worry about this job do I?"
He was right, I followed the code to the letter except the code here says I didn't need conduit, but upgrading wasn't an issue.
I'd say if you can do it, go for it. It's relaxing, gives me a bit of peace of mind that no little critters will someday chew through it, and it's one more bit of insurance for me of fire containment (doubtful, but then I'm crazy about fire prevention). Only shame was having it all covered up with insulation and sheetrock later....sigh....
Dave
I think 10 requires 3/4 inch,, At lease here it is a must..
The NEC says that you can put 5 No. 10 THHN conductors in a 1/2" EMT - youse guys in Chicago must be really different.
You should at least consider a permit. Where I live, the permit for this is well under $100, includes an optional preinstall inspection and plan review, plus an inspection prior to energizing the new circuits. Where I live, you don't have to be an electrician to wire your own home.
Another consideration is that your insurance may refuse to pay if there's an electrical fire, if there's any non-code wiring. If the wiring has been inspected and accepted by the city, your position is much better. If you ever sell your place, the buyer may bail if inspection turns up non-code wiring, or compel a fix.
Legalities aside, heck, we all make mistakes, and an inspector is a good way to possibly ferret one out before you learn the hard way.
Unless your local code is more restrictive than the NEC, you won't have to run conduit if you're putting your romex in the wall (I think the wording has something to do with the wiring not being subject to impact damage). My inspector told me that if I shielded from impact, even with wood, I could avoid conduit in my garage.
110 in a garage has to be GFCI protected, too. You can do it without replacing a standard breaker by putting a GCFI outlet closest to the box; downstream outlets will get the protection automatically.
NEC requirements for motors is a little different from requirements for appliances. Your inspector can tell you if your machines are considered appliances, but really they're motors. The main differences are, you need an accessible, marked cutoff (the breaker suffices if it's close and accessible enough) for a motor, and the ampacity of the wire has to be a minimum of 125% of the motor-plate amp draw of the motor... and the breaker can be up to 250% of the motor's draw to account for startup drain (so you can legally put a 50A breaker for a 20A motor, which your 5HP saw likely is, assuming you run cable capable of handling 50A; your cable's ampacity MUST be at least 25A). (OOPS you didn't say 5HP, that was someone else... sorry!)
Also when you're doing your calculations, to protect your motor you're going to want to use a cable/length combination that won't drop your voltage more than 2 1/2% (instead of the normally-acceptable 5%), so use the motor-specific tables when determining the required ampacity. Otherwise, you'll be prone to motor-harming undervoltage at startup and high load.
Edited 9/19/2005 9:32 pm ET by vulcan666
I guess I have been out of the "Inspection Business" for about 20 years, but to my knowledge, it might be easier to protect "Romex", if that is allowed, by running it through the studs, which is protected by drywall, whcich is the traditional method. Covering it up with wood, I don't know...how thick is the wood that you cover it up with ? Will that protect it?
I think the original poster, needs to consult an electrician, the building department, or another qualified agency, and find out exactly what applies to his circumstances. I think your advise is spot on there, ask the governing body, and then you have no future problems with insurance, etc.
BTW, I am the poster with the 5hp saw, and you don't need a 50 amp CB "circuit breaker" for that circuit, what you need is 125% of the rated name plate motor amperage, which is the start up current draw. And if you read the NEC it will tell you what the "wiring size should be", my old book, which is out of date (1980's) will tell you that in section 430. It is all about motors.
Electrical questions are always a tricky deal, if someone gets hurt, a fire is started, or worse, being "zapped" causes personal injury, who is at fault? I think if we offer any advise, other than, this is what I did, and an inspector approved it in "my location" we are treading on thin ice.
My 2 cents
Steve Pickett
You're 100% right it's better to run the cable through the studs and cover with drywall. As I said in my post, the wooden shield idea came from my code compliance guy. I didn't get more information because it didn't interest me.
As to the circuit capacity for the 5HP saw, I really wrote that badly. I mixed together two concepts: required minimum, and allowable maximum.
As you point out, the first required minimum is, the circuit (OCP and wire) be capable of 125% of the motor's rating. Less than that is a violation.
I also meant to point out that the NEC specifically allows a circuit of up to 250% of that rating. Therefore for a 20A motor, you cannot install a 20A circuit (need that 125%), so allowable circuits range from 25A (125%) to 50A (250%).
Thanks!
As you point out, the first required minimum is, the circuit (OCP and wire) be capable of 125% of the motor's rating. Less than that is a violation.
NEC 430 requires that motor circuit min ampacity be taken from Table 430-148. It's based on nameplate hp, not actual nameplate FLC. For 5 hp at 230V (single-phase), the Table calls for 28A. The reason the tabulated FLC numbers are used is that, for fixed equipment, the motor is likely to be replaced in the future with another of the same hp rating, but it is not likely to have the same nameplate FLC. So Table 430-148 gives high-side values that should cover most motors of that hp and voltage, and the wiring is not likely to need changing for a simple motor replacement.
Circuit conductors can be sized per Table 310-16, and the 15, 20, and 30A limitations on 14, 12, and 10 gauge conductors do not apply. 125% of 28A is 35A minimum which is 8 gauge at 60C or 10 gauge at 75C. But, as pointed out, you are permitted a breaker up to 250% of the Table 430-148 value, which is 70A IF you use a motor control, which Art. 430 requires.
The motor control is the overcurrent and overload protection device, NOT the CB, and IT is set based on the actual motor nameplate full-load current rating (with replaceable heaters in most cases). The CB is only there for short-circuit and ground-fault protection. The motor control protects the motor, itself, and the supply wiring. That's a big deviation from the way the NEC addresses most other wiring. There are other sections of the Code that are similar, too, like hermetic HVAC equipment.
As pointed out, you also need a disconnect, but a cord cap (plug) is a legal disconnect.
Where the whole thing gets iffy is in what you consider a table saw to be - an appliance or an industrial machine. As far as I'm concerned, a Unisaw with a UL label and factory cord and plug is no different than a vacuum cleaner. Wire up some 20A general-purpose receptacles and cut wood (assuming 12.4A at 230V, like mine). These are not permanently installed blowers, pumps, extruders, conveyors, etc. in a commercial or industrial situation. I've got five receptacles on one 20A 240V circuit - I can only run one tool at a time, after all. I'm more at risk of blowing a kitchen breaker with all the high-current appliances on our countertops, yet no one is insisting a dedicated circuit for each one (not counting appliances anchored in place, like dishwashers).Be seeing you...
Conduit (EMT) is used for exposed or surface mounted situations. If the wires are in the wall then Romex type wire is prefered. Do not pull Romex (2 or 3 wire cable) in conduit. That is specificly prohibited. As far as the wire gauges just look it up in a book. Basicly 14 ga is good to 15 amps and 12 up to 20 amps.
Mike
Do not pull Romex (2 or 3 wire cable) in conduit. That is specificly prohibited.
I can't find anywhere in th NEC where it says that. In fact, Article 336-6(b) explicitly says that Type NM Cable (aka Romex) shall be enclosed in conduit where subject to physical damage.
Anyway, I used EMT conduit in my shop (with individual THHN conductors). As a general rule, I don't use exposed Romex around here in outbuildings - too many mice in this rural area. I shudder everytime I go into a horse barn and see Romex just stapled to the framing.
EMT does give you flexibility to re-configure things later, and the conduit itself serves as the ground lead. Plus, I get a bit of satisfaction from getting the conduit bending "just right", and doing a neat and good-looking installation. But that's just me.
I don't know where or even if it states that in the books. Of course the "book" is full of information that is hard to find unless you know where it is. The inspectors in the area where I work say it is code, some times local code is more restrictive than national code. The explanation was that among other things wire is rated based on its ability to disapate heat. Romex is rated on based on open air installations, when run in conduit the heat will build up potientially causing insulation failure. Aside from that it is damn near impossible to pull Romex in conduit any way.
Mike
Well, local jurisdications can set whatever rules they want, but the explanation that Romex needs to dissipate heat makes no sense. First off, the ampacity of Romex conductors is de-rated from what they would be in free air. Also, Romex can be run inside insulated walls and ceilings. Insulation will block heat dissapation much better than metal conduit will, which actually conducts heat very well.
But hey, they get to make the rules, even rules that make no sense.
Yea who knows.
The times I've ran into it where when romex was ran into a junction box and then into bx, or conduit with out changing wire. It was cited on a remodel where this was done on a water heater. I don't really know if it is code or not, but my main electric sub said it was (as well as the inspector). And my sub is not your average electrician, he really knows his work.
But really it is a moot point as pulling romex is imposible unless there are no bends.
Mike
<!---->Thank you ALL - I learned a lot!<!---->
First, I am going to do a permit.
Second, I probably will run Romex through the walls (see below).
Vulcan666 was simply great - lots of useful info. I had already planned doing GFCI for all but it was a good reminder. And ditto on the cushion for motor startup loads.
DonStephan's suggestion to run a ground wire even if using metal conduit hit me as very smart - and made plastic conduit a much more practical choice.
MadDog33's comments were succinct but useful - although I think my idea of an "overhead raceway" might be different. Excellent advice to keep outlets over 4' high.
I agreed with Dave's comment about the therapeutic effect of pulling wires - I've seen it done in a 60' square space with 20' ceilings (I paid an electrician to wire my auto repair shop in a former life) - and it really was cool. [That electrician also taught me the advantages of "riding" the stepladder down if it goes over]
And I learned that some of you must be really muscular! Pulling 10 or 12 gauge Romex through conduit? My forearms ache just thinking about it!
What I didn't learn was any convincing reason to run conduit. I am not worried about electricity if I start running saw blades through my wall surface - I'd take that as a sign than I should stay away from all tools.
I've got lots of Romex on hand. I've planned to cut an access panel to get into the garage "attic." The walls haven't been insulated yet. So I think I can actually route the wire pretty easily - I don't even need to drill horizontally through studs, just down through the top plate.
Gotta go - I need to cut an access panel and then go take my morning shower!
You got it. We pull wire in remodels all the time and it is generally pretty easy. On the walls where the rafters meet the ceiling joists you will likely have trouble with the drill and bit fitting in the tight space. I bought a cordless right angle drill for this purpose. Mine is the 18 volt Dewalt unit, you need a powerfull low speed drill to turn a big auger bit (1/2" or 5/8"). Corded versions are not too expensive. Another trick we use is to tie one of those little keychain flash lights to the end of the wire when you drop it into the wall. That makes it esy to locate the wire from below. One complication you could have in the future is with "old work" boxes loosening. Old work boxes are the kind that have tabs that clamp the box to the sheetrock. They are about the only thing that will work in your situation. If you use heavy duty 15/20 amp outlets (recomended) the plug sockets are stiff. Over time plugging and unplugging tight fitting cords will loosen the box and eventually the box can break through the drywall. However if you locate the box right against a stud you can sink a couple of drywall screws from inside the box into the stud. That will secure the box completely.
Have fun. Glad to hear that you are doing it yourself.
Mike
Exposed romex in a garage or a workshop is subject to damage. If run behind drywall or other sheathing, romex is fine.
Since all junctions should be in boxes, most people would run wiring along the wall, rather than have junction boxes at ceiling feeding plugs down the wall. If you want to stagger circuits along the wall, individual THHN wires in conduit possibly easier. If using metal conduit, I prefer to include green jacketed ground wires rather than rely just on conduit for grounding.
Some of your questions suggest at least a consult with a good local electrician would be in order (which begs the question of determining which electrician is "good").
Conduit is a MUST where I live.. Depends on local code..
I wired my shop last year. I have 8" jointer, 2hp, Unisaw with 5 hp, 14" band saw and numerous outlets,for other "plug in tools" like 13" planer and a sanding center. In my "hobby shop" even figuring in a Promax sander, or other tools up to 5hp, a subpanel of 100 amps is good enough for me. That's because I won't be turning on and off any more that one machine at any one time.
If you got some cable to run 400 amp, it must be pretty heavy stuff, most of the time that is used in 3 phase situations.
I ran my wiring in PVC EMT conduit, because it was surface mounted and the easiest way to run it. As another poster pointer out, I was also concerned about mice etc. but also future insurance requirements.
If you are unsure in any way, talk to an electrician, I did on my own shop, and I was a building inspector for 2 years. A lot of electricaians can also steer you in the right direction, on what you loads will be and might be in the future, and where to ge the best deal on equpment. Mine did, saved me about $ 200, and help me pull the wire to my shop, in underground conduit, for about 125'. Good luck and ask questions from the professionals.
Good Luck, and stay safe,
Steve Pickett
If you are concerned about mice i'll send my wife round,
Top class mouse catcher. Non Better
Sounds good to me. Although, I have 5 dogs here right now, and am out in "God's Country"......Kansas, nearest neighbor is 3 miles away. Nothin but fields, and praire, lotsa critters. Dog's get a couple now and then, but not enough to keep up.
I've had the mice jump 3' up to my assembly table in my shop to get some jerkey, I left there overnight, in a sealed plastic bag. I put some foam insulation around the perimeter of my shop, a 100 year old school house, and they chewed thru that, about 4" thick.
She might cost me to much in food, chasing all the critters....LOL...If she likes killing the mice that much, you might want to relocate. Heh heh :-)
Steve Pickett
Conduit is as much a question of code as it is exposure. In the Chicago area, all wiring goes through conduit (and no, you would not pull romex through conduit).
Wire gauge depends on voltage, amperage and length of the wire run. Don't use 10 gauge because you have it--use it for 10 gauge conditions.
If in doubt, hire a licensed electrician!
my preference would be conduit, it adds flexibility, is more durable, and eliminates the need for a ground wire to each receptacle from the panel ,....(you must install a jumper from the receptacle cover back into the box though) you can buy pigtails for this purpose.
keep your breakers loaded for no more 80% of their rating
#12 on 20A breakers do not load >18A ....got it?
#10 for 30A ........................................>24A
unless your runs are more than 50ft. you should not need to over size your wire, this depends on the distance and amps needed, but you need to keep voltage drop to no more than 3%
there is ####VD calculator at this site, http://www.electrician.com/calculators/vd_calculator.html
running raceways overhead keeps the walls clear !
enough for now?
install your receptacles so the boxes are above four ft. from the floor to clear sheets of plywood or DW you want to stack.
"
Edited 9/19/2005 4:29 pm ET by maddog3
"...raceway overhead..."
I am not sure what you mean.
CableOrganizer.com has several cable management raceways -
enclosed surface
cable trays
wire duct
Thanks ahead of time.
Doug
I was referring to running the conduit overhead, also GD ,if you do decide to use EMT do not forget to ream, or "deburr" the cuts you make before putting the pipe together.I just read your summary and I agree, you should probably use the materials you have on hand.
Installing conduit can be a very frustrating experience the first time, maybe even the 15,000th time LOL
it also doesn't help that you have a finished ceiling to work above. Good Luck,
Edited 9/20/2005 11:55 am ET by maddog3
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