Quick question of electrical material opinion…
Detached shopgarage. All conduit will be exposed. Do you go with rigid metallic or rigid nonmetallic? Or something else?
Thanks
Mike
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Iron pipe, as all of it eventually will become hanging storage. Conduit can't carry the load that black iron can. :) Joe H
I was gonna use PVC in my workshop because the plastic looks smoother, or something. Anyway, I looked at the cost of fittings (you will use A LOT of them if you're doing a whole shop) and quickly changed my mind.
EMT stuff is cheap, way cheap, compared to the PVC stuff, at least in my area (SE Michigan).
Also, bending PVC is difficult to do unless you invest in the special heater. Using a heat gun is slow and can give very messy results. Using an EMT bender is quick and you can learn how to do it pretty repeatably.
One thing you'll get real good at is bending EMT pipe. The offset fittings (that can allow you to skip lots of bending right where you join the pipe to every box) cost 4 ~ 5 times more than the simple, straight ones ($1.25 vs. $0.27). So I bent all of mine instead.
For the lighting I used clamps that hold the EMT 1/2" off the surface to line up with all the lights' holes, but to keep it tight to the walls I bent everything and ran the pipe flush.
Hope this helps.
Plus bending EMT is fun. Just finished rewiring my detached garage with EMT. I used all 3/4" since it is cheap and a lot easier to pull wire through than 1/2". The challenge here is to avoid using couplings and do as many compound bends as you can. Looks nice but of course you end up throwing away half of what you bend :)
bit
Remember code limits your fun to a maximum of 360 degrees of bends in any one run. ;-)
I'd agree that EMT is best in the garage, but PVC for the underground run to get the power there.
-- J.S.
Yup. I know the code regarding a total of 360 degrees of bends (between pull boxes). But I doubt I could get that out of one 10' stick and have it go where I wanted it to go anyway. I cut it with a Sawzall and use a file to clean up the cut inside and out.
bit
Edited 1/13/2003 3:56:55 PM ET by Bitman
My vote is for EMT. As mentioned before, its cheaper, there are a wider variety of fittings and all of those fittings are reusable should you decide you want to change something. The benders are cheap and you can cut it easily with a tubing cutter. Just make sure you ream the inside of the tubing. That will prevent striping the wire on the sharp edges. Also, if you space your hangers right you can still hang a bunch of junk from it. LOL.
Well then let a unanimous vote be cast for electrical metallic tubing.
Use 4" square deep boxes with steel raised covers, ground tails in all boxes.
Box offsets are the hardest bend to learn because they're a matter of developing just the right touch.They're what makes a job look professional though, leaving them out just screams "HACK".
Regarding your choice: "rigid metallic or rigid nonmetallic"
A minor semantic point but there is Rigid Metallic Conduit (RMC) that looks very much like galvanized plumbing pipe. Tough stuff that uses all threaded connections. It is relatively difficult to work with, expensive and calls for specialized tools for threading it. On the up side I once worked on a building that burnt down. Most of the RMC runs were hanging in space, like tree limbs, and many were still quite live and useable.
What your probably thinking about is Electrical Metallic Tube (EMT). Popularly known as thinwall. Good stuff that, once you get a feel for it, can be quite fun to work with. While EMT is bent with a hand bender, or a knee for a slight bend in a hot attic, RMC, properly installed, could be used a chin up bar.
The one weakness EMT has, the one that may make nonmetallic a better choice, is corrosion. If you store fertilizer (ammonia), chlorinizer for the pool(chlorine) or other corrosive agents EMT will not last very long. I have seen EMT fail in less than a year where run in a pump room for a pool. The chlorine and moisture caused it to disintegrate to the point that, in spots, the wires were draped between straps.
While using 3/4" may make pulling filled runs easier and it may be justified in a few central runs I have a hard time imagining you needing enough circuits to even lightly fill a 1/2" conduit. Given well designed, try to limit the bends to three nineties, and installed, properly deburred and supported, conduit and good technique, well made heads and proper lubricant usage, I can't say I have had any great trouble pulling in wires even when pushing the legal maximum.
IBEW Berry is right. Bending EMT, especially box offsets is a matter of touch. Different brands of EMT, even one stick to another, vary in stiffness and workability enough that even experienced electricians need to have a few practice runs on scrap to adjust their technique. A talented bender will often make multiple bends, kicks and offsets in three planes and do it all reliably on a single 10' stick. Trying to do this without training and practice can eat up time and lots of EMT.
The technique I teach my help is to start with single bends or kicks and straight runs connected with couplings. Properly planned, many bends can be avoided and will look better in simpler form, you might use one or two more couplings per run. Nothing wrong with couplings. Properly installed, firm and tight not in a bend, and supported, at least one near the coupling to keep the joint in line, they do not noticeably cause problems when pulling in wires.Once you gain experience you can try putting more bends into a single piece of conduit.
If the runs are under cover use set screw couplings as they go in faster, are easy to check for tightness and are cheaper. While compression type units are good and required for the run to be weather tight unless they are made dead tight they can rotate and cause problems with alignment for less experienced installers.
Don't be thrown off of nonmetallic conduit too easily. Easy to cut, glue together and flexible enough to be threaded into holes drilled into studs it can go in easily once you get the technique down. Bending is not all that hard. A 3/4" EMT bender will make large box offsets, small ones are commonly just strapped in unless your picky like I am, and small kicks if you over bend it and let it migrate back to the form you want. Ninety degree bends can be bought or bent in with heat. A dedicated heat box or pad makes this easier but, with practice, a propane torch or heat gun can make a nice bend in minutes. Here again planning will limit the number of bends needed.
Each method has its place, strengths and weaknesses. It is good to read people asking intelligent questions up front. Mistakes made in the planning phase are easy to correct with an eraser. I see far too many people who spend thirty years cussing problems that weren't caught until after completion.
That's one comprehensive reply Lorn. Good answer. BUT........I want to add one thing :)
PVC expands and contracts noticably with temperature swing, sags, and discolors in sunlight. Particularly the small diameters (1/2" or 3/4"). After some time passes it can look like s...
So, emt gets my vote .
Ed
As always, you guys are great! Thanks for the variety of replies and obvious wealth of experience. I was a contractor by trade but can fill all I know about electrical work in a single gang box. One of the small 17 cubic inch ones at that!
Looks like EMT is the way to go although I really like the look of gray PVC. Ran the supply lines out to the shop in 2" underground and have used PVC more than I have EMT but neither enough to be called proficient let alone knowledgable. Hence my original question posting.
So I still have some decisions to make although it seems I'm leaning towards the EMT...but I really like the look of the PVC ;)
Thanks again folks!
Mike
I should have explained myself a little better. When it comes to electrical I am a DIYer. I learned from my dad who was an electrician and from reading books like Wiring a House by Rex Cauldwell (Taunton). Planning is everything when it comes to wiring. So when I ran my circuits from my sub panel to the back of the garage I used 3/4" EMT so that I could run multiple circuits at the same time. I also added an extra circuit in 2 of my runs so that future upgrading would be easier. I have no single circuits in EMT so 1/2" was unnecessary (everything ends up in the wall with Romex). Code does not require a separate ground in EMT but I ran one anyway just to be safe.
I do have a question though. I have one circuit that has a receptacle next to my SP but then continues its run to the back of the garage. The wiring for that circuit enters the SP from both the Romex for the single rec and the conduit for the run. Do I need to splice the neutral with a pigtail to the neutral bus or can I have both neutrals go right to the bus? Of course the hot is spliced and pigtailed to the breaker.
Thanks,
bit
Bit,
Well.... technically you're not allowed to make joints in a panel enclosure with the hot or neutrals.Or land two wires on a breaker.To follow the letter of the code you could intercept the conduit run before the panel,and relocate the recptacle that's fed with romex there.One hot and neutral per circuit into the panel.
I'd worry about taking care of this when you reach the bottom of the "Anal retentive concerns I must obsess over..." list.I'm sure you're quite safe.
I'm currently putting 8, 220 lines in my shop with pvc. I'm in SE Michigan also, and everything is less expensive then emt except the boxes, but I don't need any. I've bought everything at lowes and the savings is at least 25%. As for bends, get a couple of sticks of the flexible pvc or plastic conduit and use it cut up to whatever length you need. You may need to check in with your local inspector on that one. It just my opinion, but not being an electrician using this stuff everyday, the pvc is just so much easier to work with. Pvc is 4 or 5 hours work rather then 2 days work. By the way, I ain't cut my fingers on pvc yet either! 8^) Also my shop is a 160 year old building that use to be a blacksmiths shop. Thinking about what the pvc might look like in a couple of years made me chuckle. It's not something I need to worry about. That's for sure! Some areas around here will not let you use pvc between the weatherhead and the panel though. Might want to look into that also if that might effect you. Good luck.
Don
one more piece of information for you all (regarding shop wiring):
Mulberry makes metal 4" covers (for recepticles and switches) that are pre-painted with a high gloss grey finish, and at $0.85 each are almost the same cost as the plain galvanized ones at Lowes/HD. The only source around me (in Ann Arbor) is a commercial electrical supply house (so you have to take time off work to go there during business hours and buy them) but they look SO NICE in my shop it'll be a shame to get them all dirty when I start to using the shop for what its meant for!
Norm
Barry
QO breakers in the 15-20 and maybe 30 amp or rated for 2 wires.
"Well.... technically you're not allowed to make joints in a panel enclosure with the hot or neutrals"
Is that specifically referenced in the code. My understanding was that you could do it if you ment the fill requirements. And of course it is done all the time for pannel replacments.
Gee, Bill, all I can tell you is what our local inspectors reference and enforce.As to putting more than one wire on a circuit breaker, 110.14(A) says "Terminals for more than one conductor...shall be so identified." After I read your post I got out a handful of GE and SquareD breakers and none of them say you can put more than one conductor under the terminal.Two wires on a circuit breaker here is a turn down.
As for joints in a service panel,that's also cause for rejection here,as is having conductors enter the panel from one pipe and exit via another.On a residential service change if cables aren't long enough to make it into the new panel we have to make joints in a junction box and then enter the panel.The inspectors cite 312.8 which starts out "Enclosures for switches or overcurrent devices shall not be used as junction boxes,auxillary gutters, or raceways for conductors feeding through...."Then it does a 180 and gives fill percentages for conductors, splices and taps.I guess our AHJ just enforces the first part.
This is a PITA rule and that's why I was kidding Bit about it not being a big deal.
Barry
Barry
I have a catalog sheet on the QO breakers.
On the bottom of the page they give list the wire sizes.
For QO single pole breakers 10-30amp the list #14-8 AL, #14-8 copper, or TWO #14-10 copper.
Note that is only for the "standard" single pole version. It does not include the 2 pole, tandem, GFI or other versions.
"Enclosures for switches or overcurrent devices shall not be used as junction boxes,auxillary gutters, or raceways for conductors feeding through."
Two problems with. First is say for CONDUCTORS FEEDING THROUGH. You can still splice the conductors that have to do with the circuits having to do with that switch or overload device. If you could not have a splice in a box with a switch then you would have a lot of problems with much house wiring. You would be limited to having only having switch legs.
But #2, that is not what it says. At least reading from NEC 99. One of the problem is the way that the sentence is construction. "Enclousures for switched or overcurrent devices shall not be used as junction boxes (or ....) UNLESS ADEQUATE SPACE for this is provided. Then it goes on and device what adequate space is.
Edited 1/15/2003 11:42:18 PM ET by Bill Hartmann
Then you're QO breakers are listed for two conductors but are they identified as the code says?
There must be some reason the code writers didn't just say you can't exceed 75% of the cross-sectional area with conductors,splices,and tap in an overcurrent device enclosure.Why start the sentence by saying they shall not be used as junction boxes?
Barry
First let me give you some background. By schooling I am an electrical engineer, but I have always worked in the electronics end. Anything over 5 volts is "high voltage". Now days most of my work is with software, but it is controlling water pumps, from a few hp to over a 1000 hp. But I don't get envolved with that.
My personal experience has been working on my house and that of a friend. where I am they don't care what you do unless you are building a new home or extending the exterior and then you need inspections.
So I don't have experience with the code over the years which sometimes gives some clues to the hidden meaning of the some of the wording. Also I am not really up on all of the interactions between the different sections of the code.
As far a splicing in the pannels my friend hired an electrican to put in a new pannel and upgrade the service. I would have like to tackle it, but I knew that I would have the service out for 3 weeks while I got it all figured out and I would have to wait for the power co to make the new connections. He hot wired the new service and then a couple of week later the power company upgraded the drop.
Anyway he spliced a couple of the runs in the new pannel. (2 of which I since replaced when I split and reworked some of the old circuits). And I an online friend of mine that is also an electrican and he has said that he also does splices in the pannel.
Here are 3 threads from Mike Holt that discuss one or both of these.
http://www.mikeholt.com/forum/Forum1/HTML/005319.html
http://www.mikeholt.com/forum/Forum1/HTML/005115.html
http://www.mikeholt.com/forum/Forum1/HTML/005390.html
Hi "All" -
I recall, vaguely, an electrical job many years ago on which the electrician had a couple of wooden fixtures (for different sized tube) for making the offset bends in EMT from the wall to the connector on the box. He would put the EMT in a slot, make a bend with the usual EMT bender and then flip the tube to make another bend and presto, a perfect offset. The fixture enabled him to make the bends with a minimum of fit and try. Try as I may, I can't remember now just how it worked.
Anyone know what I'm talking about? I'm interested because I'm planning on using surface mounted EMT to wire my new shop and would prefer to look at nice bends when it's all said and done. I'd really appreciate any info on how to rig up one or two of those jigs to make it a little faster, easier and more uniform. Thanks!
Ron
Ron,
Greenlee makes just what you're looking for. It's called "Little Kicker Offset Bender" and there are two models: One for 1/2" EMT and the other for 3/4" EMT. [Catalogue numbers 1810 and 1811.
However the price is somewhat high -- around ~$160.
Bending conduit is fun and is one of the few things that separates the professional electrician from a DIYer. I make pencil marks at 2" and 5". Bend it 10º at the first mark and 10º at the second mark the other way to make your offset.
~Peter
A little bit of practice, and you can do offsets in seconds without any measuring or hassle. Usually, an offset is a short piece, so even if you do it 5 times, you only waste a couple feet of conduit.
Sometimes you can pick up a bunch of small scrap from a construction site to practice with. If not, 1/2" conduit is cheap.
Just get a normal bender. Take a short length of conduit. Slide it into the bender so the front of the conduit is even with the front of the bender lug. Push down quick, just a little bit. Rotate conduit 180 degrees slide forward 3-4 inches. Push down quick, just a little bit. Cut off the part you need and clean the edges. With a little practice, you can get the hang of how far to push for different offsets.
One of the best skills the army taught me was bending conduit. First they taught us how to mathmatically do it. Measure 36" up, 24" Right, 20" straight, or whatever. Use the formulas, cut a piece to length, mark where to bend and bend it. It works. Takes about 15 minutes to do the math with practice. Another couple to mark up the conduit and bend it.
Then they just had us practice just doing it. Much faster. Little more waste. Waste amount decreases with practice. Most common mistake is bending a corner the wrong direction. NEC States a max of 360 degrees of bends in a length of conduit. There is no rule on # of conduit splicers you put in. Often, you'll bend the perfect complex shape, but it's a couple inches short somewhere, or a corner goes up instead of down. Cut the correct part out and add a splice piece. Not as satisfying as bending a complex run out of one tube, but perfectly legal and functional.
Above all, have fun. I love working with conduit.
I totally agree. I don't measure for box off-sets either. I was just writing for the guy who apparently hadn't done it before. That's why I put in the measurements.
Another trick is to support it 3' from the box and go straight in.
~Peter
Well, don't know how well I did, but I just wanted to encourage people to try it. Bending offsets isn't nearly as hard as things most people do everyday, but lots of people see it as more difficult then it is. I know I did before I sacrificed a few lengths of conduit. Always like to encourage people to try new things.
I assume when you say support it you mean just put some small blocks of plywood under it so you can fasten it to the wall. Good fast way of doing things.
One of my favorite quotes:
"A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects." -- Robert A. Heinlein (No I can't do all these things)
I don't agree with the person above who suggested to support the EMT on blocks to avoid the offset bends. That looks too much like an amateur job, I think!
One more pointer, for those learning to bend EMT, is to check the offset of your boxes before you get too far along.
Sometimes you'll find that the offset from the panel, the lights and the 4" device boxes, will all be a little different. If you get all bendy before you start installing things you will find that some parts are offset too much and some are not enough.
The good EMT bender from GB has a bubble level and degree marks on it for very quick reference and make it possible for you to do without any jig (a 2x4 is handy as a spacer when bending opposing bends near to each other).
It is a great feeling when you bend a complicated shape and don't get any of the bends backwards and the whole thing lines up! (tip - EMT is pretty forgiving and you don't have to be PERFECT for things to look darn near perfect when its all screwed down).
Get yourself some good screws for this, don't use crappy drywall screws (another sign of an amateur). Get galvanized, hex head, self drilling screws with a spinning washer for the best effect (the spinning washer helps to prevent the torque of the screw from twisting your boxes & clamps so that you can get everything all nicely lined up).
Norm
Good suggestion on the screws.
Hey, I'm an oddball. I love to bend conduit. I try to make things out of it in my shop, just because I enjoy it. I have some friends that are electricians, and they just look at me like I have two heads when I tell them I like to work conduit.
I intend to rewire my garage in conduit. Love being able to easily change things latter. Particularly in a shop. Though as much as possible, I'll put the conduit behind drywall, in the ceiling, ect. Got enough hiding places for dust, bugs, and spiders as is. Hate to surface mount everything and add to this problem. Worth time and work of replacing a few pieces of drywall. Need to buy me a 3/4" bender still. So far, for personal stuff I've gotten by with the 1/2" bender.
For anyone who wishes to totally avoid offsets, and not have it look cheezy and unprofessional. Go to an electrical supply store, or mcmaster.com, and buy some strut channel and conduit clamps. Mcmaster# 3310T46 $9 for 5'. Conduit clamps are less then $1 each. Cut about a 4-6" length of channel, attatch to wall and clamp the conduit to it. You'll have to make sure to buy boxes that match the offset of the channel. Handy stuff. you can mount just about anything to it. But, it'll add quite a few dollars to the total project amount.
the offset clamps are fast, but they cost something like 5 ~ 10 times what the normal clamps cost:
$0.29 each for normal clamps
$1.50 for offset clamps
I did the math and bend my own offsets!
If you can get better pricing (there can be BIG differences, depending on many factors) then go for it.
Norm
You got me curious. McMaster pt#8081K41 1/2" $1.21 ea. $1 ea. for 10 or more. 3/4" $1.73 for 10 or more. Still, for the cost of a couple offsets, you could learn how to do it with a bender.
What I've always gotten a kick out of is the local lumber yard that sells 90 degree bends of conduit for $5+ each. McMaster charges $1.65 ea.. Heck of a money maker. I could make piles of these in a few minutes with a couple dollars of conduit and a hand bender. Even at $1.65, add in 2 couplings and you've paid about $2.50 for each bend in your conduit.
Seems to me, even if you're gonna only do a little bit of conduit work, a bender easily pays for itself. Aprox. $18. Unscrew a piece of 3/4" pipe from a pipe clamp and you have a handle. I've also made simple racks to store rolls of wire on, a rail for a carry rack on a 3 wheeler, made handles, and other things. Conduit is good for lots of things other then putting wires in. Think it's just me though. I started a thread called creative conduit once hoping to get some good ideas on neat uses for conduit. Didn't get much response, though there were some good ideas.
http://forums.taunton.com/n/find/findRedir.asp?webtag=tp-breaktime&mg=34AF5DDD-DB5B-4893-A7A6-DB49083D777B
Dear Mr. Graham,
When I mentioned supporting the conduit 3' from the box -- this is the [usual] legal maximum. At that distance, there is enough flexibleness in 1/2" conduit and slack in the connector that it will go into the hole at a barely perceptable angle.
There are things known as "Conduit Hangers" or more commonly "Minnies" which are roughly a U shape with some wiggles at the bottom and then a rounded part which fits around the tube and then flat ends with a screw and nut which clamps it shut. I did not suggest the use of plywood spacers but that is also a possibility.
I bend my box offsets myself.
~Peter
Just ran acrost this site yesterday. http://ourworld.compuserve.com/homepages/boyce_smith/offset.htm
Good explination of how to bend offsets. For those who want to make it precise. Measure it off and mark where to bend. Then use the multipliers listed here.
The cosecant of 15 degrees is 3.89
The cosecant of 30 degrees is 2
The cosecant of 45 degrees is 1.4
So, if you want a 3" (30°) offset make a mark. Times 3" x 2. Then mark 6" from first mark. Bend a 30° angle at the first mark. Flip conduit 180°, and bend at the 2nd mark 30°. If your bends are accurate, you'll have bent a 3" offset.
Once most people bend a few offsets, they forget the math and just eyeball it.
Hi -
The last post reminds me that I haven't reported back on my "bending" experience. My shop required about 250 feet of EMT, 70% 3/4" and the rest 1/2'". With a total of 22 outlet boxes (1900 boxes) and half as may junction boxes, the job required only 1 coupling (on a 13' run).
After the first five or six bends and a sacrificial length of tubing I was soon on automatic as I moved along. I messed up two or three pieces with asymmetrical bends but by and large I was very happy when the electrician congratulated me on a job well done. We pulled all the wires without grease.
I used a box with a 1/2" and a 3/4'" connector attached to it check the offset and bent most of the 1/2" tubing on a 21" high work bench so I didn't have to bend over so much. I invented a couple of fixtures to help out but abandoned them as a waste of time after using them just a few times. The most useful tool I had was the Bosch sabre saw which should be classified as a WMD (it puts my Milwaukee Sawzall into the toy category). It was great for cutting off the EMT quickly and was incredibly accurate when it came to trimming as little as 1/16" off a too-long piece.
The whole experience was a lot of fun and very satisfying.
Ron
Edited 6/5/2003 11:04:44 PM ET by ronw
Glad you enjoyed it. I really like working with conduit. Pretty simple once you've done it a few times. You're right you just go on automatic pilot and go for it. Glad it turned out well. Bending offsets on the bench was a good way to save your knees and back.
Helped my BIL finish up some wiring in his basement last night. He still can't believe I actually like to do this stuff. He'd really think I was nuts if he knew I liked to do conduit too.
I keep hoping to get to redoing the wiring in my garage (er. shop). I have lots of components stockpiled: Lights, ceiling fans, conduit, fittings, outlets, ect. Just need to buy boxes. Can't wait to actually start bending some conduit. Want to redo the wiring, add some circuits. First I want to tape the drywall and paint the walls and ceiling white. Both to make it brighter, and to get rid of all the spider cracks, so they're easier to find and kill before they get so many cobwebs everywhere.
Was gonna just live with the poor lighting ect. in my garage until I got my shop built. Started realizing I'd probably need about $10-15,000 to just get the concrete in and the shop closed in. Decided I'm liable to be using the garage as my shop for a long time to come. Time to figure things out and get going.
Hey, you're good at this now. How are you at drywall seams. You do the drywall, and then I'll tutor you so your conduit bending really gets good.<G>
I'm with you, BILLYG83440, I enjoy wiring (and a few other things) but HATE painting. No good reason for it.
But friends who will think nothing of tearing up a whole room to change the color scheme will be in 'awe' of someone who is not afraid of re-wiring an outlet!
Funny how life is like that.
Norm
Yeah, my BIL is just eating up hanging the sheetrock, now that the wiring's done. When I wire he just hangs at my elbow trying to figure it out. A good thing, as long as he doesn't do any himself.
I'd much rather wire then hang sheetrock. Actually hanging it isn't bad, it's after you do that and get the mud out that I don't like.
Of course, his teenage son won't touch the wiring. He'll tear an engine apart for fun, or spend all day running wire & building boxes for new speakers in his car, but pulling electrical wires 'really sucks.' Go figure.
Embarassing last night though. Put in an exterior outlet and swapped the black and neutral wires. Both screws looked silver in the light we had. Must have saw a silver screw and put in the white wire, then shoved the black wire in and tightened without looking. Don't think I've ever done that before, so of course I do it when someone's watching.<G>