Electrical question on using conduit part II

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Thanks to everyone who responded to my earlier query on conduit. BTW, can anyone suggest a good practical reference on using EMT and other conduits? I have "Wiring a House" by Rex Cauldwell, but that really only covers NM cable. I also purchased the 2002 NEC, but that's not a practical reference.
My last point of confusion is this: I want to put in a horizontal run of boxes to the left of the panel, but immediately to the left of the panel are two vertical 2x4s. They are part of a narrow stud wall built just to support the panel. How should I deal with this?
I assume I should just drill through the two 2x4s. That would be alot easier and require way fewer bends than going out somewhere else. Should I butt the first box up against the 2x4s and use NM-B just for this first run? Or should I use conduit?
For conduit, what type of conduit and connector should I use, in the interest of minimizing the hole size? Everywhere else I'm using 3/4" EMT with setscrew connectors, but I assume that would be a poor choice. There will 7 #12 wires, EGC plus 3 circuits, and the knockouts in the relevant area of the panel are all 1/2" only. So perhaps 1/2" conduit would be best for this very short run?
Any advice would be much appreciated, there seem to be too many options relative to my experience.
Thanks, Wayne
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Yah
This in a unfinished basement inna residence for a handful a branch circuits......
Last I heard the requirement for any conduit at all was for commercial use only...
String nm cable under the joists, and down the walls, leaving them exposed and just be done with it.
If the next owner dont like it then offer to disconnect and abandon the branches at the service panel before he takes possesion.
Local codes may vary, so be sure to check with your permitting authority.
HTH
--

SVL



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...

I respectfully disagree. Reason is: Exposed NM right on a wall surface doesn't pass the "subject to damage" test. I'm in the office now, so I can't quote chapter and verse of the NEC on it, but if I remember right, NM cable (a.k.a. Romex) always has to be protected by something (like a layer of drywall, some wood, conduit, etc.) at heights below 7', even in basements. Obviously, this does not apply in areas that are never used, like non-standing-height attics.
I'll try to look up the section in the NEC tonight at home.
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wrote:

use
exposed
No prob, lemme know what you find--I would like to see it as basically this is how I wired our shop out of the top of the service panels and going up to the ratrace, and the local inspector passed the job and he even put a personal note on the ticket for me "Nice job!!!" or somesuch........
Do note the top of the panels is at appx 5'6" though, and NOT at bench height.
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"subject to physical damage" is really a judgement call. There are usually some local guidelines but thwe final answer is always going to be common sense or the inspectors opinion, not always the same thing. ;-) The compromise is Smurf tube (ENT) or MC cable.
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some
or
Hi Greg.
I exaggerated a little mainly to get the ball rolling and to let the OP realize there are other easier and less expensive methods is all--not that I have any doubts a mettallic raceway isnt probably the most durable setup.
As I said before, I have kinda taken a liking to using emt and then transitioning to the liquidtite flex at a handy box
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Just remember when you transition from metal to PVC you have to have an equipment ground in the pipe and you need to bond all metalic fittings, boxes and raceways down stream.
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boxes
I m talking about the flex, it has a metallic inner liner with outer pvc jacket.
And I always run a continuous ground from the equipment to the panel grounding bussbar.
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You can always use PVC but you don't get that industrial look guys like.
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On Thu, 23 Sep 2004 11:16:13 -0700, _firstname_@lr_dot_los-gatos_dot_ca.us wrote

Ralph,
I respectfully disagree in part with your respectful disagreement - Rx does not always have to be protected by a layer of something at heights below 7':
Article 336 specifically allows using NM for exposed work. It must be run in accordance with 336-6, which calls for protection from physical damage where necessary by conduit, guard strips, etc. Except for passing through a floor, no specific definition of where the cable would be subject to physical damage is given.
NM run in accessible attics has the same requirements as given in 333-12 for AC cable (guard strips under certain conditions), which also references 300-4(d) (protective plates if cable is less than 1 1/4" from stud surface).
You will find the 7' rule in 333-12(a) which calls for guard strips if the cable is run across the face of rafters or studs within 7' of the floor or joists in accessible attics. There is no exemption for "non-standing-height" attics, if they are accessible.
There is no 7 foot rule for unfinished basements.
However, I'm certainly far closer to your position than that of PrecisionMachinisT. Under 336-6(c), in unfinished basements, you have to protect NM "under the joists" unless it's larger than 8-3 or 6-2. Smaller cables have to be run through bored holes or on running boards. Under 300-4(d) NM run on the exposed face of studs has to be protected. If it is run on the side face at least 1-1/4" from both surfaces, it does not.
In the proposed installation, the question of whether and where the cable is subject to physical damage would be up to the AHJ. I have worked on many installations with exposed NM in unfinished basements, garages and attics which passed. It does take a bit of care to route the NM properly, and many DIY installations are inadequate.
All of that being said. I agree that the proper wiring method for this basement workshop is EMT, and I'm glad the OP is designing it that way.
Regards,
Kenneth
As a
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[ long and detailed discussion omitted for the sake of brevity. It comes down to: You can really run exposed NM cable a.k.a. Romex in unfinished basements on the walls. ]
You made me go down to my basement (currently being finished!) and get the NEC, and look up all the references. You are indeed completely correct. For some reason, I had stuck in my mind that the 7' rule applied everywhere, and it really is only for attics.
That having been said: If I were a building inspector, and I saw exposed NM on a flat surface in a wood shop (where people move sheets of plywood and long wood pieces around, and push heavy cast iron tools on mobile bases), I would insist on protecting the NM cable. Unfortunately, article 336-6(b) never defines what "physical damage" might mean.
Here is a slightly scary story. When talking to the chief building inspector (the plan checker), he suggested that I use explosion-proof wiring for my wood shop in the basement finishing project. He even pointed out that wood dust in the air does indeed make my 200 sqft shop qualify to be a class II group G hazardous location --- which would have made wiring it just about impossible for an amateur. He relented when I pointed out that (a) all the wiring will be in stud walls, behind drywall, (b) a small residential shop is not a hazardous location (in the NEC sense), and classifying it as such would be at least very unusual. Then he suggested that I get a dust collector to exhaust the dust to the outside; and I showed him that a location for that dust collector was already identified in the plan, and that a dedicated circuit for it will be provided. He really liked that idea. In this climate of extremely eager (one might even say over-eager) building inspectors (a.k.a. the authority having jurisdiction), I'd rather be safe than having to redo the job.
By the way, on another topic: There was a short discussion of box fill calculations. From my experience: A box that is too full or close to the limit according to the NEC calculation is also no fun to wire. Doing it the first time, with all new wire, is doable but tough. But if you ever have to redo it later (add more stuff, change the connections), it gets to be absolutely no fun. After trying to jam too many wires into boxes a few times, I gave up, and got a lot of larger boxes, and even retrofitted them in a few places.
But also, the box fill calculation in the NEC is a little too simplistic. Here are two examples on opposite ends of the spectrum. A wire that simply runs straight through a box counts for one allowance (typically 2.25 cu in for 12-gauge). That's silly, because a wire that goes straight through uses up next to no room, sits flat against the back of the box, and doesn't get in the way. Similar argument for internal clamps, which also cost one allowance, yet the typical Romex-clips that are found in metal outlet boxes use up nearly no room, sit on the edge of the box, and don't get in the way.
On the other hand, a device on a yoke counts for two allowances, independent of what size it is. For a non-grounded light switch (which is very thin) or a normal side-wired 120V outlet, this makes sense. But the same rule applies to really big and fat devices, for example a GFCI with 5 wires attached (2xline, 2xload, ground), or a 4-way light switch (also 5 wires), or a L14-30 outlet (4 wires, each 10-gauge). Trying to push those big devices into a box that's already near the fill calculation limit is not fun, and is really asking for trouble (wires and fingers usually get pinched). In those cases, really deep boxes (2 1/8 deep), or even the oversize boxes (I think they are 4 3/4" square rather than 4" square) are your friends. Extension rings are a second-best solution (because their flange gets in the way).
I'm also not sure I understand the progression of volume allowances. It is 2 cu in for 14-gauge, and only goes up to 3 cu in for 8 gauge. But to me, it seems that 14 gauge is so much easier to handle, in particular because you take a bundle of them, even with a wirenut at the end, and bend them into a nice twisted loop to store them in a box. I'd hate to work in a box that's filled to the NEC limit with solid (not stranded) 10-gauge and 8-gauge conductors, that must be murder.
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On Thu, 23 Sep 2004 21:57:59 -0700, _firstname_@lr_dot_los-gatos_dot_ca.us wrote

I certainly agree that exposed NM in a woodshop is not good design, even when run according to the code (which, it is often observed, is comprised of minimum safety requirements - and is not a design manual.)

That's an interesting point. There have been several lengthy discussions on professional electrician's discussion boards about the classification of home wood shops. IMHO it is extremely unlikely that the concentrations of airborne wood dust in a normally ventilated home shop would truly qualify as hazardous. Certainly all reasonable means should be taken to keep airborne dust minimized, not just for electrical safety, but for your health!

I agree that the code box fill requirements are often a bare minimum rather than the optimum for installation and maintenance. In particular, the 2 wire allowance for strap mounted devices seems slim for GFCI receptacles, as you observed. I believe that the cubic inch requirements are based on conductor cooling needs rather than ease of wiring. I personally always use deep boxes (2 1/8") and often use the 4 11/16" square instead of the 4" square - the cost increase is minimal compared to the savings in installation labor and increased ease of maintenance.
I enjoyed reading your lengthy and thoughtful posting.
Kenneth
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How do I count a switch on a yoke (box fill wise)? My "Illustrated Guide to the NEC" tells me 2 conductors for a switch and 2 conductors for a yoke as if they were separate counts. According to my math that would be 4, but that would make me exceed the box capacity for a fairly simple 12 AWG wiring. I'm also not sure if there are any devices that don't have a yoke at all.
Thanks,
Thomas
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2 wires per device, that is a yoke and everything on it equals 2.
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snipped-for-privacy@auzinger.org Wrote:

Most switches are mounted on a strap and most receptacles are mounted on a yoke. Look at these devices from the side and the origin of the names will become apparent. You only deduct the two wires from the box fill for each yoke or strap no matter how many devices are on that yoke or strap. The two volumes you deduct are for the largest wire that is terminated on that yoke or straps devices rather than the largest wires in the box. -- Tom H
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Time to consider a bigger box. Or change the wiring so that you only have one cable at the box/switch location.
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Thanks for all the responses. Knowing that I only have to count 2 conductors per device makes a difference of 18 cu in in my 4 gang box of 60 cu in (43.5 versus 61.5). I'm supplying 2 bathrooms with 2 20 Amp GFCI circuits (recess shower light needs GFCI I think), so I have to run 2 NM12 cables through this box. I realize I could get by with 15 amp for the lights and 20 amps for the receptacles, but I already fished all the wires.
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2 conductors for one yoke.
If you are calulating the actual cubic-inches with the 12awg, then it's 2x2.25
Just what I remember....

later,
tom @ www.FindMeShelter.com
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On Wed, 22 Sep 2004 22:24:30 -0700, Wayne Whitney wrote

Wayne,
Not sure why you're running 3/4" EMT. 1/2" is rated for up to 9 #12 THHN conductors, and that's not a hard pull by any means. If the studs are there only to support the panel and are not otherwise load-bearing, just drill them for the 1/2". A 1/2" right-angle drill and ship-auger bit is the preferred tool...
As to books on wiring methods: there's the American Electrician's Handbook by Croft, and Practical Electrical Wiring by Richter. They're both expensive, so I'd try to take a look at them first before buying to see if they're useful to you.
Good luck.
Kenneth
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rather than cutting a big hole for a fitting next to that panel perhaps just use a 90 deg connector or LB out of the panel bottom (or top)

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