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| Home Repair (alt.home.repair) For all homeowners and DIYers with many experienced tradesmen. Solve your toughest home fix-it problems. |
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#1
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Electrical questions on using conduit
Hello,
I'd like to add some receptacles in my unfinished basement for using the space as a workshop, and my understanding is that I need to use conduit. I'm comfortable wiring circuits using NMB cable, but this will be my first time using conduit, so I have several questions. 1) My default idea is to use EMT, but there seems to be a confusing number of different types of raceways. Can anyone point me to a good overview of them? 2) My understanding is that is acceptable to use EMT as the equipment ground, but is it still a good idea to run a separate EGC? If I do so, I assume that I should bond every box to the EGC. Does it matter if the EGC is bare or green? 3) The wall is concrete for the first 4' and then a wood stud cripple wall covered in 1/2" sheer paneling. I don't have any experience fastening to concrete, what is the best way to go? It would be easier to attach to the sheer paneling, but I expect 4.5' is too high to be convenient for receptacles. 4) I'd like to run two 120V circuits. What are the pros and cons of having them share a neutral versus having separate neutrals? One appealing option is to use two duplex receptacles in each box, each fed from a different leg. I believe this requires a double pole breaker? Thanks, Wayne |
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#2
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In article , Wayne Whitney wrote:
4) I'd like to run two 120V circuits. What are the pros and cons of having them share a neutral versus having separate neutrals? I believe I've figured this one out--since the circuit will require GFCI protection, using a shared neutral would require an expensive 240V/120V GFCI breaker. So to use 120V GFCIs, I'll have to use separate neutrals. Cheers, Wayne |
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#3
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Wayne Whitney wrote:
In article , Wayne Whitney wrote: 4) I'd like to run two 120V circuits. What are the pros and cons of having them share a neutral versus having separate neutrals? I believe I've figured this one out--since the circuit will require GFCI protection, using a shared neutral would require an expensive 240V/120V GFCI breaker. So to use 120V GFCIs, I'll have to use separate neutrals. Cheers, Wayne You would not necessarily *have to* use separate neutrals. You could use separate GFCI's. Bob |
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#4
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This is Turtle.
Reply below ----- I only run EMT on HVAC systems and a electricians here maybe able to answer better. "Wayne Whitney" wrote in message ... Hello, I'd like to add some receptacles in my unfinished basement for using the space as a workshop, and my understanding is that I need to use conduit. I'm comfortable wiring circuits using NMB cable, but this will be my first time using conduit, so I have several questions. 1) My default idea is to use EMT, but there seems to be a confusing number of different types of raceways. Can anyone point me to a good overview of them? I think you confussing me here now. I only know of 2 types of races ways. 1) Indy 500 Race Way 2) Electrical Race way. A Race Way is a shelf made for wires or conduit, covered electric route for wires , or a bunch of wires in conduit run together to be neat and look good. I really only know one type of race way as far as you looking up the conduit verses the wires to put in it or the rating of the wire. Now you can have the wires out of coduit or in conduit in a race way but you just rate the wire in free air or in conduit and the race ways it just the holder for the conduit or the wire. Just rate and figure everything in EMT and forget the race way thought. 2) My understanding is that is acceptable to use EMT as the equipment ground, but is it still a good idea to run a separate EGC? If I do so, I assume that I should bond every box to the EGC. Does it matter if the EGC is bare or green? In a residentiual job like your. The Ground can be green or the Nake ground can be used. I don't know of any requirement to tie the ground to the EMT but let the EMT be it's own grounds. I don't know about using the EMT as the ground but in commercial it is a NO NO. I don't think I would do that. 3) The wall is concrete for the first 4' and then a wood stud cripple wall covered in 1/2" sheer paneling. I don't have any experience fastening to concrete, what is the best way to go? It would be easier to attach to the sheer paneling, but I expect 4.5' is too high to be convenient for receptacles. Get you a box of Wall Ackor set and drill hole in concrete with the bit supplied with it and put in a wall ankor and the clamp it with a screw [ supplied with the kit ] to put a EMT wall clamp to hold the EMT. This is not a big deal at all and a wall ankor kits cost about $6.00 for a 100 Ankors, 100 screws, and one drill bit for concrete. You can put the EMT where ever you want with the kit and conduit. 4) I'd like to run two 120V circuits. What are the pros and cons of having them share a neutral versus having separate neutrals? One appealing option is to use two duplex receptacles in each box, each fed from a different leg. I believe this requires a double pole breaker? Your making a mountain out of a mole hill here. Everything [ receptical wise ] that is tied to 1 -- single 120 volt service breaker can share the Hot , Neutral, and ground. You don't need a double pole breaker for anything here. Thanks, Wayne Now you have left out here the most important thing of all. What are you wanting to run or plug into these receptical and what will be the amp draw of them? Do you want 2 circuits with 2 breakers or all on one circuit ? You head of the game here by doing the wiring and have no ideal of what it will need as wire or conduit needed. Alway tell or know what you want to supply with power before running power to it and then finmd out you don't have the circuit big enough to supply the load. Let us know what you want to power up before wiring begins. TURTLE |
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#5
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Wayne Whitney wrote:
In article , Wayne Whitney wrote: 4) I'd like to run two 120V circuits. What are the pros and cons of having them share a neutral versus having separate neutrals? I believe I've figured this one out--since the circuit will require GFCI protection, using a shared neutral would require an expensive 240V/120V GFCI breaker. So to use 120V GFCIs, I'll have to use separate neutrals. True. Here's why: Because you are in a basement, you'll need GFCIs. This means either a GFCI breaker (big $$$), or an outlet GFCI. But you want two circuits. This either means you get a 2-pole GFCI breaker (about $100), and then you can run a single neutral, or you use two outlet GFCIs. But if you use two outlet GFCIs, you can not merge the neutrals back together again. In our case, we were forced to wire with a single neutral, because I wanted to use plugstrips (made by Wiremold), and those have a single neutral and two hots. So we were forced to use the $100 2-pole GFCI breaker. Compared to the other costs of finishing the whole basement, and building the woodshop, the cost of the breaker is insignificant. In article , zxcvbob wrote: You would not necessarily *have to* use separate neutrals. You could use separate GFCI's. Yes, but you can only use the separate neutral until you get to the first GFCI in the daisy-chain. After the GFCI (that is, on the load side of the GFCI), you can't merge the neutrals back together. If you try, the GFCIs will trip all the time. So the suggestion of a single neutral with cheap outlet-style GFCIs only works if you never use the load side of the GFCIs. And if you want to have lots of outlets, the GFCIs will add up. -- The address in the header is invalid for obvious reasons. Please reconstruct the address from the information below (look for _). Ralph Becker-Szendy |
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#6
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#7
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Wayne Whitney wrote:
In article 1095826040.700496@smirk, wrote: True. Here's why: Because you are in a basement, you'll need GFCIs. This means either a GFCI breaker (big $$$), or an outlet GFCI. But you want two circuits. This either means you get a 2-pole GFCI breaker (about $100), and then you can run a single neutral, or you use two outlet GFCIs. But if you use two outlet GFCIs, you can not merge the neutrals back together again. OK. But if you have a separate GFCI receptacle for every receptacle, i.e. you never you the LOAD screws on the GFCI receptacles, then you could get away with a shared neutral? Of course, all those GFCI receptacles quickly add up to the cost of a GFCI breaker. Cheers, Wayne Actually, you can use the LOAD terminals, but it can get confusing pretty fast so it's not necessarily a good idea -- you can't have a shared neutral on the LOAD side of any device. I can think of a good example where you might want to do this. Lets say you want two new 20A 120V circuits in your garage, and your garage is 100 feet from your breaker box. To reduce the voltage drop when you're operating 2 heavy loads at once, run 12-3 cable to the first double-gang outlet box and install 2 GFCI outlets. Run half the outlets in the garage from the load side of one GFCI and the other half from the load of the other GFCI. You have to run separate neutral wires from this point on. Bob |
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#8
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In article ,
Wayne Whitney wrote: I'd like to add some receptacles in my unfinished basement for using the space as a workshop, and my understanding is that I need to use conduit. I'm comfortable wiring circuits using NMB cable, but this will be my first time using conduit, so I have several questions. 1) My default idea is to use EMT, but there seems to be a confusing number of different types of raceways. Can anyone point me to a good overview of them? The best overview of what you CAN LEGALLY do is the NEC itself. It is not exactly written for easy reading. Combine that with a good electrical supplies catalog (for example the Grainger catalog), to show you what is available and the costs of things, and you'll figure it out. Note: I didn't suggest buying everything at Grainger ... just to use their catalog as a reference guide. Nothing wrong with Grainger, but the local Borg is cheaper. In practice, there is only one option: EMT. The stronger conduits (IMC and rigid) are much harder to use, may require threading of the ends, and don't give you any real advantage (unless you intend to drive vehicles into the walls). The grey plastic conduits, which are glued, are quite brittle and will not survive long in something like a shop. And they are actually more expensive and more work to install than EMT; their advantage is that they are waterproof, but who cares. Blue smurf-tube (officially known as ENT, or Electric Nonmetallic Tubing) is so wimpy, you wouldn't catch me dead running AC power through it; plus I don't think its up to code for exposed work anyhow. It is suitable for low-voltage (computer and phone wiring) in non-exposed locations, and that's about it. OK, I lied. There is a second option, but it is a little weird: Wiremold and some competitors make squarish raceways, that is usually clipped together out of a base (that you screw onto the wall) and a cover. You have to then use the matching outlet boxes. Advantages: A more finished look. And you can get the surface raceway prewired and pre-assembled with electrical outlets. Disadvantages: The smaller models have very little room for wire; the bigger ones look very bulky. EMT has a more industrial look; the surface-mount raceway always has the look of "retrofit in cheap construction" to it. EMT is probably strong (will sustain less cosmetic damage occasionally being hit when you swing a sheet of plywood around in the room). You can get a huge variety of EMT fittings and boxes for it at any hardware store, while only electrical distributors and mail-order have a good selection of fittings for surface-mount raceways. And the wiremold stuff is quite pricy (all these little $2 and $4 items add up quickly). 2) My understanding is that is acceptable to use EMT as the equipment ground, but is it still a good idea to run a separate EGC? If I do so, I assume that I should bond every box to the EGC. Does it matter if the EGC is bare or green? Would you trust your life to sheetmetal? Even worse, would you trust your life to using iron (that rusts!) as a conductor? Here's my policy: I always run a separate ground conductor for outlet circuits; not necessarily for lighting circuits (where there is very little chance of touching energized circuits). This is overkill from a NEC and code point of view, but I like it. You need to eventually bond every box and every bit of metal conduit to the ground conductor. But they don't all need to be bonded directly to the copper grounding conductor. I like to always bond the boxes that are reachable, with a dedicated ground pigtail (not by using the metal-to-metal contact from the outlet strap). Also, if a grounding conductor runs through a box, it is easy to loop it around the grounding screw once, so many boxes get grounded for free. But for boxes that are not normally reachable (like the one at the top of the conduit, out of reach), and the conduit itself, I'm happy to rely on the metal-to-metal contact of box to conduit for grounding (as long as a significant fraction of the boxes are bonded). None of this dedicated grounding is required by code (AFAIK), but it makes me feel better. If you are pulling dedicated wire (typically THHN), it is actually easier to pull green insulated wire - it seems to slide better. I only use bare copper conductors if the wire in the conduit is the long stripped end of a Romex (NM-B) cable. Also, I always worry about having uninsulated wires in outlet boxes. What if they get bent wrong, and touch the exposed hot or neutral screw at the side of an outlet? This could cause hard-to-debug intermittent shorts or ground faults. I'm nervous enough as it is when using NM-B, so I try to avoid it when using conduit. 3) The wall is concrete for the first 4' and then a wood stud cripple wall covered in 1/2" sheer paneling. I don't have any experience fastening to concrete, what is the best way to go? It would be easier to attach to the sheer paneling, but I expect 4.5' is too high to be convenient for receptacles. Actually, I've been told that in a shop area, it is convenient to have outlets relatively high (above the benches and worktables). So I have planned a continuous ring of Wiremold plugstrips along the wall at 4' height. The 220V outlets (for bigger machinery) and a few extra 110V outlets are at the usual 16" height. Other people, other styles, and other usage patterns might have different opinions. Here is another question: If you can hide all your wiring in the stud wall (above 4' height), then you probably don't need conduit at all. As far as I know, the only reason conduit is typically required in a basement is that you can't run NM-B in exposed locations, and basements are typically concrete or block walls, which forces you into exposed wiring. This might save you lots of work. Lastly, how to attach things to concrete: This is really easy: Make holes in the concrete, and use plastic anchor. The problem is that in practice this is hard and expensive. First, it is a tad hard to get really good plastic anchors in the US. The typical red conical ones are quite wimpy and unreliable. I like using the "Fischer" brand grey plastic anchors from Germany, which are considerable stronger and more reliable, but those you'll have to get mailed to you by friends in Germany (or oder them from Amazon.de, and pay horrendous shipping charges). And then you'll have to get the matching metric drill bits. Second problem is how to make all the little holes (typically 1/4" or 5/16" holes for plastic anchors. The easy but comfortable solution is to buy a pneumatic drill hammer; they are made by Bosch, Milwaukee, Hitachi and so on, and start at about $200. They always have SDS or spline attachments for the drill bits. The nasty but cheap option is to buy a hammer drill, which uses a normal chuck. Drilling holes with a hammer drill is very annoying (it rattles your arm, and makes terrible noises). Using masonry bits in a non-hammer drill is a non-starter; with lots of patience you can make a hole or two, but it is pointless for mass production. Good luck! We're in the middle of our basement finishing project. Fortunately, because we are adding a lot of stud walls, nearly all the wiring is NM-B inside the walls. -- The address in the header is invalid for obvious reasons. Please reconstruct the address from the information below (look for _). Ralph Becker-Szendy |
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#9
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In article ,
Wayne Whitney wrote: .... OK. But if you have a separate GFCI receptacle for every receptacle, i.e. you never you the LOAD screws on the GFCI receptacles, then you could get away with a shared neutral? Of course, all those GFCI receptacles quickly add up to the cost of a GFCI breaker. Let's see. One extra roll of 12-gauge THHN at Home Despot: $5. For 8 of the 10 outlets you install, use a $7 GFCI instead of a $1 outlet (you need the first two GFCIs anyhow). You do the math (you are in the math department after all, I'm just a physicist who is already burned out and trying to prevent getting himself electrically fried in addition). By the way, given your location, I recommend that you do your parts shopping at the Lowe's in Union City, or at Orchard Supply. They seem to be much better organized than the Home Depot's around the Bay Area. Matter-of-fact, today I gave up on a trip to the Capitol Expressway Home Depot, because half the stuff I needed couldn't be found, and the checkout line for the only register that was open wrapped halfway around the building. I'll drive to Gilroy or Union City for Lowe's instead, get the stuff at OSH (more $$$ but less chaos), or frequent the local hardware store. -- The address in the header is invalid for obvious reasons. Please reconstruct the address from the information below (look for _). Ralph Becker-Szendy |
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#10
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In article , TURTLE wrote:
"Wayne Whitney" wrote: 1) My default idea is to use EMT, but there seems to be a confusing number of different types of raceways. Can anyone point me to a good overview of them? Just rate and figure everything in EMT and forget the race way thought. OK, I guess I used the wrong term, I meant to say "different types of conduits". Sounds like EMT with THHN wire is the way to go, I was just curious about the alternatives. Now you have left out here the most important thing of all. What are you wanting to run or plug into these receptical and what will be the amp draw of them? Yes, that's true, I was trying to get a handle on EMT before I got to the details. Thanks for the responses. Here my situation: the main loads will be a table saw (15 amp 120V universal motor), planer (15 amp 120V universal motor), dust collector (8 amp 240V induction motor) and jointer (6 amp 240V induction motor). [BTW, both the DC and jointer claim to 1 HP. Is the jointer motor really 25% more efficient?] There will also be a 120V air compressor and miscellaneous portable tools. I was planning on 1 240V 20 amp circuit and 2 120V 20 amp circuits, because other than the dust collector, I'll mostly be using these tools one at a time. I'm happy to have the jointer next to the dust collector, so they can share a duplex receptacle. My planned physical layout is this, along a 20' wall: Quad 120 Quad 120 Quad 120 Electrical Panel Duplex 240 My preference would be for each quad 120 to be two duplexes on separate circuits. I'm a little confused about running multiple circuits in the same conduit. Namely: Are there any rules that if multiple circuits are in the same conduit or box, they have to be shut off by the same breaker? Is there anything special about having a wire run through a box without being tapped? If I run 2 separate 120V circuits in one conduit, do I end up with two white wires and two black wires? Or am I supposed to use different colors for each wire? If I run all three circuits in one conduit, then that's 6 conductors plus ground. Do I have to derate the conductors, and does that mean using #10 gauge THHN for a 20 amp circuit? Thanks, Wayne |
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#11
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In article ,
zxcvbob wrote: Actually, you can use the LOAD terminals, but it can get confusing pretty fast so it's not necessarily a good idea -- you can't have a shared neutral on the LOAD side of any device. I can think of a good example where you might want to do this. Lets say you want two new 20A 120V circuits in your garage, and your garage is 100 feet from your breaker box. To reduce the voltage drop when you're operating 2 heavy loads at once, run 12-3 cable to the first double-gang outlet box and install 2 GFCI outlets. Run half the outlets in the garage from the load side of one GFCI and the other half from the load of the other GFCI. You have to run separate neutral wires from this point on. Completely agree. Oh, and in addition, you might want to run 10-3 cable to feed the garage (copper is expensive, but still cheaper than the aggravation of having an annoyingly substandard electrical system, for the next 30 years). As an example: A few circuits in the my basement shop are being run with 8-3 cable, even though they are just 220V 30A circuits. It's just that for the largest power users (the table saw I want to buy eventually), I want to have spare capacity and no voltage losses. Our basement will have three 110V outlet circuits. One feeds most of the rooms except the shop. It goes from the panel to a GFCI outlet right next to the panel, and from there on only to regular outlets (one long daisy chain, so there is no confusion). The other two come off a 2-pole GFCI breaker (mucho bucks), and feed a 2-circuit Wiremold plugmold strip that covers most of the walls in the shop, all wired with 12-3 cable. I just hope that the various building inspectors agree with our opinions. -- The address in the header is invalid for obvious reasons. Please reconstruct the address from the information below (look for _). Ralph Becker-Szendy |
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#12
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According to Wayne Whitney :
I'd like to add some receptacles in my unfinished basement for using the space as a workshop, and my understanding is that I need to use conduit. I'm comfortable wiring circuits using NMB cable, but this will be my first time using conduit, so I have several questions. 1) My default idea is to use EMT, but there seems to be a confusing number of different types of raceways. Can anyone point me to a good overview of them? EMT is probably superior, but your inspector will probably not require it. My shop has NMD along the bottom of joists, plus short stubs of PVC to the outlet boxes. All surface mounted. The NMD along the bottom of joists is acceptable because there's lathe there protecting it (for later installation of drywall on the ceiling). 2) My understanding is that is acceptable to use EMT as the equipment ground, but is it still a good idea to run a separate EGC? If I do so, I assume that I should bond every box to the EGC. Does it matter if the EGC is bare or green? Don't rely on the EMT for equipment ground. The NEC apparently permits it in residential, but our codes forbid it. Green or bare. 3) The wall is concrete for the first 4' and then a wood stud cripple wall covered in 1/2" sheer paneling. I don't have any experience fastening to concrete, what is the best way to go? It would be easier to attach to the sheer paneling, but I expect 4.5' is too high to be convenient for receptacles. It wasn't in my shop. 4) I'd like to run two 120V circuits. What are the pros and cons of having them share a neutral versus having separate neutrals? One appealing option is to use two duplex receptacles in each box, each fed from a different leg. I believe this requires a double pole breaker? I did this slightly different. I sent over three shared neutral four wire circuits. Each supplies two outlet boxes, each box has one duplex (but split) receptacle. No circuit supplies two adjacent boxes. A total of 12 outlets, each 120V circuit supplies only two, not on the same box. Oodles of power. Six circuits tho ;-) No GFCI. I'd have to use dual GFCIs here. -- Chris Lewis, Una confibula non set est It's not just anyone who gets a Starship Cruiser class named after them. |
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#13
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"TURTLE" wrote in message ... This is Turtle. Reply below ----- I only run EMT on HVAC systems and a electricians here maybe able to answer better. I have started using that liquidtite flex conduit with the grey pvc outer jacket in a lot of places. Still prefer the EMT type for the longer straight runs and that, but then I put inna handy box here and there and drop or go around a corner with the flex.......... -- SVL |
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#14
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#15
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In article ,
Wayne Whitney wrote: Here my situation: the main loads will be a table saw (15 amp 120V universal motor), planer (15 amp 120V universal motor), dust collector (8 amp 240V induction motor) and jointer (6 amp 240V induction motor). [BTW, both the DC and jointer claim to 1 HP. Is the jointer motor really 25% more efficient?] There will also be a 120V air compressor and miscellaneous portable tools. One of these days, you will go to a good tool store (I suggest CB tool in San Jose, but the place in Alameda isn't half bad either). You will come home with a 3HP Unisaw, General or Powermatic in your truck. At that point, you'll need a 240V 30A circuit. And you'll be kicking yourself for not providing one. Suggestion: Wire the 240V outlets with 10-3 cable. It is quite a pain to wire with, but will save your sanity in the long run. You can continue to use a 20A breaker and 20A outlets, just use heavier wire as insurance for the future. As mentioned before, I went further overboard, and used 8-3, which is quite a pain to use (I'm dreaming of a General 650 with a 5HP motor). Are there any rules that if multiple circuits are in the same conduit or box, they have to be shut off by the same breaker? No. Is there anything special about having a wire run through a box without being tapped? No. Just run it through. Technically, there is no need to leave extra slack. If the box isn't very crowded, I like to make a loop in wires that just run through; so far I've never needed to use that loop, so this is probably a waste of time. If I run 2 separate 120V circuits in one conduit, do I end up with two white wires and two black wires? Or am I supposed to use different colors for each wire? Yes, you get two blacks and two whites. This is a bit confusing, so I like to use a Sharpie and put red or green or blue marking on the wire, at the ends. Or make a flag with white electrical tape, and write a description on it. This is not code necessary. I've seen one industrial installation being done by professionals, and they didn't bother marking any of the wires (takes too much time). On the other hand, they installed everything right the first time, they had wire tracing tools to identify the ends, and they don't tinker endlessly with their installation. YMMV. For the hot conductors, you could buy red (and blue and mauve and ...) wire. Unfortunately, for the neutral conductors, you have to use something that is mostly white. In principle, white wire with a colored stripe exists, but I've never seen it for sale (other than in industrial quantities). If I run all three circuits in one conduit, then that's 6 conductors plus ground. Do I have to derate the conductors, and does that mean using #10 gauge THHN for a 20 amp circuit? Yes, you have to derate the conductors. I just went down to the building site in the basement (also known as the desaster area), and got the NEC. Article 310, table 310-19, note 8: You have to derate to 80% for 4-6 current-carrying conductors, and to 70% for 7-9. But, don't despair: The allowable ampacity of 12 gauge THHN wire is either 25A or 30A (depending on whether the things you attach at the end of the wire are rated to 60 degrees or 90 degrees C). And 80% of 25A is 20A, so you can continue to use 12 gauge wire. If you have 7-9 conductors, I find the code confusing (not clear whether the 70% rule applies to the 90 degree rating, because the conductors have been separated by the time they are attached to 60 degree rated things like breakers and outlets). And you don't count the grounding conductor, and you maybe don't count the neutral conductor (note 10 to the same table says that it doesn't need to be counted, but only if the neutral carries only the unbalanced current, and there are no nonlinear loads, so I wouldn't chance it). By the way, with 6 conductors plus ground (of which some might end up being 10 gauge), I would go to 3/4" conduit. 1/2" conduit would probably be legal (it can technically handle nine 12-gauge conductors), but installing it would be a royal pain. And nearly all outlet boxes have both 1/2" and 3/4" knockouts, so it is easy. And: Finding a copy of the NEC (could be slightly outdated version) at a used bookstore is an excellent idea. -- The address in the header is invalid for obvious reasons. Please reconstruct the address from the information below (look for _). Ralph Becker-Szendy |
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#16
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wrote in message news:1095831266.920726@smirk... For the hot conductors, you could buy red (and blue and mauve and ...) wire. Unfortunately, for the neutral conductors, you have to use something that is mostly white. In principle, white wire with a colored stripe exists, but I've never seen it for sale (other than in industrial quantities). Theres no reason to identify the neutral conductors, these all attach to the same bussbar in the breaker panel anyways. -- SVL |
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#17
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There's one other factor I haven't seen mentioned in this thread. As I
understand it, you're only allowed to share a neutral between two circuits that are on different phases. Greg Guarino |
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#18
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Wayne Whitney wrote in message ...
1) My default idea is to use EMT, but there seems to be a confusing number of different types of raceways. Can anyone point me to a good overview of them? I've only used EMT, and only 1/2" at that. It's reasonably easy to work with, but as with anything else, there's a learning curve. In fact, it's the "curves" that require the "learning". I've seen installations where people used elbows and offset couplers instead of bending the pipe. In fact, I had to run wire through such an installation once. It was a real pain in the neck to thread the wire through. You have to open each elbow in the run. A conduit bender lets you form nice smooth curves, once you get the hang of it. For me the hardest part was learning to get the offset bend (a small "jog" in the conduit that brings it a little away from the wall as it goes into a box) to face in the correct direction. Buy more conduit than you need to account for errors. You'll also need a rattail file small enough to smooth out the inside edge of the conduit pieces. Otherwise the wire insulation can be damaged by the sharp edge. Other people on this thread have suggested running larger wire for possible future needs. That may be a good idea, but you should probably get yourself a good book or other reference to let you know how many of what gage wire are permissible in the size conduit you choose. Or, preferably, how to choose the right size for the wires you intend to install. 3) The wall is concrete for the first 4' and then a wood stud cripple wall covered in 1/2" sheer paneling. I don't have any experience fastening to concrete, what is the best way to go? It would be easier to attach to the sheer paneling, but I expect 4.5' is too high to be convenient for receptacles. I think that electricians tend to use Tapcon screws. They are probably a little less work than the plastic anchors I usually use. Greg Guarino |
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#19
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Wayne Whitney wrote:
Hello, I'd like to add some receptacles in my unfinished basement for using the space as a workshop, and my understanding is that I need to use conduit. I'm comfortable wiring circuits using NMB cable, but this will be my first time using conduit, so I have several questions. 1) My default idea is to use EMT, but there seems to be a confusing number of different types of raceways. Can anyone point me to a good overview of them? EMT and surface mount boxes. 2) My understanding is that is acceptable to use EMT as the equipment ground, but is it still a good idea to run a separate EGC? If I do so, I assume that I should bond every box to the EGC. Does it matter if the EGC is bare or green? I use green, except in large (#6 or larger) gauges. EGC isn't required, but is a good idea. 3) The wall is concrete for the first 4' and then a wood stud cripple wall covered in 1/2" sheer paneling. I don't have any experience fastening to concrete, what is the best way to go? It would be easier to attach to the sheer paneling, but I expect 4.5' is too high to be convenient for receptacles. Tapcon screws. If you plan on doing a bunch of fastening of things, a hammer drill makes short work of it. If you get a box of 100 Tapcon fasteners, they come with the drill bit. You'll be able to attach other stuff to the concrete walls with this as well. 4) I'd like to run two 120V circuits. What are the pros and cons of having them share a neutral versus having separate neutrals? One appealing option is to use two duplex receptacles in each box, each fed from a different leg. I believe this requires a double pole breaker? You've come across the reasons. I'll suggest stranded wire, as it is easier to work with, and prevents the usage of el-cheapo back wired outlets. Since you can buy wire by the foot at the borg, I suggest color coding the wires, different colors for each circuit. |
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In article ,
PrecisionMachinisT wrote: wrote in message news:1095831266.920726@smirk... For the hot conductors, you could buy red (and blue and mauve and ...) wire. Unfortunately, for the neutral conductors, you have to use something that is mostly white. In principle, white wire with a colored stripe exists, but I've never seen it for sale (other than in industrial quantities). Theres no reason to identify the neutral conductors, these all attach to the same bussbar in the breaker panel anyways. In theory, correct. In practice, it is just too easy to make mistakes. A mistake that is easy to avoid would be to use a 14-gauge neutral conductor (for a lighting circuit with a 15A breaker) for the 20A outlet circuit (which needs 12 gauge). Another mistake is if you have several circuits in the same conduit and you scramble the neutrals, so in the end most of the outlets from several circuits use just one neutral wire (which is overloaded now), while the other neutral wires are heavily underutilized. If you have multiple white conductors of the same gauge in a box, this can happen easily. -- The address in the header is invalid for obvious reasons. Please reconstruct the address from the information below (look for _). Ralph Becker-Szendy |
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In article ,
Wayne Whitney wrote: In article 1095831266.920726@smirk, wrote: One of these days, you will go to a good tool store (I suggest CB tool in San Jose, but the place in Alameda isn't half bad either). What's the place in Alameda? The Japan Woodworker, 1731 Clement Ave, Alameda. Specializes in Japanese hand tools (I'm beginning to salivite just thinking about them), but also has a good selection of big machines. OK, if I use 3/4" EMT and have 6 #12 THHN conductors plus ground in it, and I want to pull out two #12 conductors and replace them with #10 or #8, how hard would that be? My entire conduit run is a straight 15 feet, it should be a relatively simple install (once I figure out all the nuances of conduit). Through 15 feet of straight conduit: trivial. Even if there are other conductors already in place. Probably don't even need a fish tape, just push the wire through (maybe get a piece of solid wire to use as a fish, then use it to pull stranded wire through). If you had said "50 feet of 1/2" conduit, with 3 ninety-degree bends, already stuffed", I would have said: Hard but doable (you'll have skinned knuckles afterwards). Our worst experience with this was pulling three 2/0 conductors (about 1/2" of copper each, for a 200A service) through about 70 feet of 1 1/2" conduit, with a few bends. We ended up with one person pushing like mad, and filling the conduit with wire pulling lubricant, and the second person using their full 200 lbs weight as a gravity operated human winch. Took all afternoon, and afterwards all our hands were a big mess. It is very hard to hold on to wire that has been smeared with lubricant, so you keep sliding off, and hitting the sharp metal edges. Much fun. Should have used 2 inch conduit instead. Good luck! -- The address in the header is invalid for obvious reasons. Please reconstruct the address from the information below (look for _). Ralph Becker-Szendy |
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In article ,
Wayne Whitney wrote: I was under the impression that it is not OK to make a connection between a screw and a wire by wrapping the wire around it like that. Perhaps I am mistaken, or there is an exception for the EGC? Tell me more about that. If that's really true, I'll have to redo a lot of boxes before the building inspector shows up. I'll check into it. Thanks for the tip. BTW, when would I want to use something other than THHN? Inside conduit, in practice, never. The only single-conductor wire that is commonly sold is THHN. And the wire inside NM-B is also de-facto THHN (even though it is not labeled such, it has to be rated to 90 degrees). Clearly, extension cords, outdoor underground feeders, and machine tools are a different story. Now, at the top of the concrete wall, there is a 3.5" ledge, then 1/2" plywood shear panels I recently installed, then an insulated cripple stud wall. I didn't want to put anything in the cripple wall as I expect the shear panels should be not be cut. I could fir out the cripple wall and run NM-B horizontally at a height of 72", say, and then drop down to metal boxes at 48" high with conduit stubs. Is that any easier than a single horizontal conduit run at 48" high? I would imagine it wouldn't be. Looks like more work to me: You have to build all the furring or soffit to hide then NM-B in, then you have to cut and connect all the conduit stubs, and you still have to worry about getting the NM-B in and out of the conduit (easiest way is to put a small handy-box there). You would end up with way more pieces, and need more wire. By the way, several posters mentioned Tapcon screws. I've used them for things like hanging shelving. But when I pulled my permit, the chief inspector (Santa Cruz county) said that even though the Tapcons are rated for structural use, and have ICBO evaluation reports, the building inspectors hate seeing them, because the tend to wiggle loose if you hit them a few times, or if something connected to them vibrates. So I have avoided them where it matters - just to avoid trouble with the inspector, and switched to plastic anchors (for non-structural things, like electrical boxes and plumbing) and steel anchors (for all structural stuff). This might be a general statement, or it might just be one inspectors pet peeve, don't know. -- The address in the header is invalid for obvious reasons. Please reconstruct the address from the information below (look for _). Ralph Becker-Szendy |
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wrote in message news:1095876588.198387@smirk... In article , PrecisionMachinisT wrote: wrote in message news:1095831266.920726@smirk... For the hot conductors, you could buy red (and blue and mauve and ...) wire. Unfortunately, for the neutral conductors, you have to use something that is mostly white. In principle, white wire with a colored stripe exists, but I've never seen it for sale (other than in industrial quantities). Theres no reason to identify the neutral conductors, these all attach to the same bussbar in the breaker panel anyways. In theory, correct. In practice, it is just too easy to make mistakes. A mistake that is easy to avoid would be to use a 14-gauge neutral conductor (for a lighting circuit with a 15A breaker) for the 20A outlet circuit (which needs 12 gauge). Another mistake is if you have several circuits in the same conduit and you scramble the neutrals, so in the end most of the outlets from several circuits use just one neutral wire (which is overloaded now), while the other neutral wires are heavily underutilized. If you have multiple white conductors of the same gauge in a box, this can happen easily. IIRC, the OP mentioned he would only be running 2 outlets, with one or perhaps two neutrals. -- SVL |
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On Tue, 21 Sep 2004 18:03:18 -0700, Wayne Whitney wrote
(in article ): Hello, I'd like to add some receptacles in my unfinished basement for using the space as a workshop, and my understanding is that I need to use conduit. I'm comfortable wiring circuits using NMB cable, but this will be my first time using conduit, so I have several questions. 1) My default idea is to use EMT, but there seems to be a confusing number of different types of raceways. Can anyone point me to a good overview of them? 2) My understanding is that is acceptable to use EMT as the equipment ground, but is it still a good idea to run a separate EGC? If I do so, I assume that I should bond every box to the EGC. Does it matter if the EGC is bare or green? 3) The wall is concrete for the first 4' and then a wood stud cripple wall covered in 1/2" sheer paneling. I don't have any experience fastening to concrete, what is the best way to go? It would be easier to attach to the sheer paneling, but I expect 4.5' is too high to be convenient for receptacles. 4) I'd like to run two 120V circuits. What are the pros and cons of having them share a neutral versus having separate neutrals? One appealing option is to use two duplex receptacles in each box, each fed from a different leg. I believe this requires a double pole breaker? Thanks, Wayne Wayne, If NM is allowed as a wiring method in your jurisdiction, then it can generally be used for exposed work in an unfinished residential basement, but not where it could be subject to damage. You can protect it with running boards, or sleeve it in conduit as necessary. However, for a workshop, IMHO, you're wise to consider another wiring method. It will make for a safer and more workman-like installation. In answer to your questions 1) In addition to EMT, the common raceway types are Rigid, Intermediate Metal Conduit (IMC), Rigid Non-Metallic Conduit (NMC), Flexible Metal Conduit (FMC or Flex), Armored Cable (AC) and Metal-Clad Cable (MC). Rigid and IMC are heavywall aluminum or steel pipe used in various hazardous locations or where subject to extreme damage. They are difficult to bend and install and are over-kill for your proposed application. NMC is a gray PVC pipe available in Schedule 40 or Schedule 80 wall thickness. It is joined by solvent cement and is relatively easy to install. It must be fastened within 3' of each box and every 10' otherwise. There is an assorment of boxes and fittings available in PVC which solvent weld to the pipe, or you can use conventional metal boxes and attach the pipe with a male threaded adaptor and lockring. NMC obviously does not provide a grounding path. Flex is made of an interlocking spiral of aluminum or steel strip. It is relatively easy to install but difficult to fish. It must be fastened within 12" of each box and every 4 1/2' feet, but for a neat installation it is usually supported at much closer intervals. It provides a grounding path if the conduit and fittings are listed for grounding, otherwise it may only be used as the EGC where the ground return path does not exceed 6'. AC and MC look like flex but come as an assembly with conductors installed. They are available with different conductor combinations: 14-2, 14-3, 12-2, 12-3 are commonly available. AC does not include a grounding conductor, instead it has an internal bonding strip which is folded back and clamped in each fitting to assure the ground path. MC includes an insulated grounding conductor. Both types provide a grounding path. AC must be supported like Flex but MC may be supported at 6' intervals. AC must have plastic "anti-short" bushings installed in the cut ends where they attach to a clamp or fitting. I personally like using EMT, but installing it can be tedious. Bending becomes easy after 10 years of practice, but initially there's a lot of wasted pipe. You probably should consider NMC or MC as your wiring method. For two circuits of #12 THHN conductors, 1/2" NMC, EMT, or Flex will be comfortably adequate. 2) Yes, EMT is acceptable as the EGC, but it provides a better ground return path to include a bare or insulated grounding conductor. And yes, every box must be bonded, generally by looping one of the EGC's around the grounding screw before nutting the EGC's together. If you don't run an EGC, then any receptacle's ground terminal must be pigtailed to the box, unless the receptacle is identified as suitable for grounding through the box-mounting screws. Even then it's good practice to pigtail them - it guarantees the ground path even if the mounting screws are loosened or removed. 3) To anchor to concrete, you'll need a percussion (hammer) drill and a suitable bit. You can use a regulary rotary drill and masonry bit, but the drilling will be tedious. You can use metal anchors and screws or masonry screws alone (Tapcons). I prefer the Tapcons. They're expensive, but save time and make a very firm connection. I buy them in bulk, but I've seen them in boxes of 100 with the appropriate bit included. 3/16" x 1 1/4" would be the right size for box and conduit straps. They have combination hex and phillips heads. Use a hex drive for installation - it takes a bit of torque. 4) For a home workshop, two 20 Amp receptacle circuits for plug and cord tools sounds like a good plan. Running both circuits to each quad box and splitting the receptacles between them is also good design. This plan also allows you to install a 220V receptacle in any box, if you should eventually need that. You do not need a double pole CB just because there are two circuits in each box, even if you use a multiwire (Edison) circuit with a shared neutral. If you do have a 220V receptacle in the circuit, or split a single duplex between the circuits (ie: two circuits feeding a device on the same yoke), then you need a double-pole CB. However, there's nothing to prevent you from using a double-pole and it's not a bad idea. As to multiwire branch circuits: I happen to like them, they save copper and help with box and conduit fill. However, they have the drawback that if the neutral becomes disconnected, and you have devices plugged-in to both circuits, the connected devices will be "two-twentied". Just make your neutral connections carefully, particularly at the panelboard neutral bus. The other drawback to Edison circuits is that GFCI receptacles will not work on them. In a residential basement, you should be using GFCI protection. You can only run the common neutral to the first pair of GFCI's - from then on the neutrals must be split. On the subject of GFCI's: The most economical design is to use a pair of them in the first box and then use their Load terminals to feed conventional duplexes in all the other boxes. This protects the downstream receptacles, and costs much less than GFCI CB's. However, if you want to install a 220V receptacle anywhere "after" the GFCI's, this won't work. In that case, you'll need a 110/220V GFCI CB to protect the circuit. One additional thing to consider for a workshop is whether you should run a feeder to a "sub-panel" in the shop, and then run your branch circuits from there. If you think you might eventually expand this installation with additional circuits, it might not be a bad idea, particularly if it's a long run to the main panel. I should probably give you the standard caution about contacting the "authority having jurisdiction" for the specific requirements in your area, pulling a permit, inspection etc. Nonetheless, I'm aware that sometimes electrical work is done without this legal requirement, and sometimes it's even safe and workman-like. Do some reading on the proper installation for the wiring method you choose. There are plenty of good books on home wiring. The place to learn is definitely not Home Depot. Be wary of advice in this NG as well (including mine for that matter). There's a lot of scary misinformation posted on electrical questions... Good Luck, Kenneth |
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In article , zxcvbob wrote:
Wayne Whitney wrote: In article , Wayne Whitney wrote: 4) I'd like to run two 120V circuits. What are the pros and cons of having them share a neutral versus having separate neutrals? I believe I've figured this one out--since the circuit will require GFCI protection, using a shared neutral would require an expensive 240V/120V GFCI breaker. So to use 120V GFCIs, I'll have to use separate neutrals. Cheers, Wayne You would not necessarily *have to* use separate neutrals. You could use separate GFCI's. Not on a 240/120 circuit, you can't. Doesn't work. |
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Doug Miller wrote:
In article , zxcvbob wrote: Wayne Whitney wrote: In article , Wayne Whitney wrote: 4) I'd like to run two 120V circuits. What are the pros and cons of having them share a neutral versus having separate neutrals? I believe I've figured this one out--since the circuit will require GFCI protection, using a shared neutral would require an expensive 240V/120V GFCI breaker. So to use 120V GFCIs, I'll have to use separate neutrals. Cheers, Wayne You would not necessarily *have to* use separate neutrals. You could use separate GFCI's. Not on a 240/120 circuit, you can't. Doesn't work. It can if you do it right. It won't work if you need a GFCI protected 240V device. Otherwise, you can even mix 240V unprotected outlets and 120V GFCI outlets and 120V-outlets-connected-to-the-GFCI-load-screws, all on one edison circuit. (it may not meet local codes to mix 120V and 240V outlets on a branch circuit, but that's not the point.) As long as the only return path for the hot LOAD wire of a GFCI is back to the neutral LOAD screw of the same device, it will work. The GFCI will not even know it is sharing a neutral LINE wire. Bob |
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This is Turtle.
Reply below and try to sort it out. Now you have left out here the most important thing of all. What are you wanting to run or plug into these receptical and what will be the amp draw of them? Yes, that's true, I was trying to get a handle on EMT before I got to the details. Thanks for the responses. Here my situation: the main loads will be a table saw (15 amp 120V universal motor), planer (15 amp 120V universal motor), dust collector (8 amp 240V induction motor) and jointer (6 amp 240V induction motor). [BTW, both the DC and jointer claim to 1 HP. Is the jointer motor really 25% more efficient?] There will also be a 120V air compressor and miscellaneous portable tools. I was planning on 1 240V 20 amp circuit and 2 120V 20 amp circuits, because other than the dust collector, I'll mostly be using these tools one at a time. I'm happy to have the jointer next to the dust collector, so they can share a duplex receptacle. My planned physical layout is this, along a 20' wall: Quad 120 Quad 120 Quad 120 Electrical Panel Duplex 240 This is a bit of over kill here but your not paying for labor so go for it. Now the wires run for the jointer & dust collector. i would just run one set of wires for the 230 volt service wire to the two of them and have a receptical for each. Both can share the wire / breaker as they both will be connected very near each other. Wire size / breaker size will have to be dealt with other than this talk. Now the table saw and the planner in my opinion should have their own seperate service of 120 volts and have each a breaker by theirself. Planner one set of wires and breaker and a set of wires just for the table saw's 120 volt service. You will have 2 service sets of wires for the table saw and Planner. Then one set of wires / breaker for the DC and Jointer with 2 recepticals. You will have 2 black wires / 1 green or nake ground wire to be joined at the 2 receptical. We have not cover wire size yet. My preference would be for each quad 120 to be two duplexes on separate circuits. I'm a little confused about running multiple circuits in the same conduit. Namely: Are there any rules that if multiple circuits are in the same conduit or box, they have to be shut off by the same breaker? Is there anything special about having a wire run through a box without being tapped? NO and NO Now tring to figure out what set of wires go to each of the 120 volt services or equipment. you can paint one set of wires for one of the pieces of equipment with spray paint about 1 foot at the end to tell which is which. Now really it will not make much difference for your only going to have 2 blacks / 2 whites and 2 ground wires. The two whites and the ground at the switch box are going at the same place and then one black wire to each of the equipment. It don't take much to figure it out for there is only 3 wire for each and different colors to boot. Just get one black to each piece of equipment and the white & Ground to the receptical. To each piece of equipment you will have ground/common/ Black. If I run 2 separate 120V circuits in one conduit, do I end up with two white wires and two black wires? Or am I supposed to use different colors for each wire? You will have 2 black wire , 2 white wires, and 2 Green or Nake ground wires. Then 1 Black [hot wire]/ 1 white [common ] / 1 Green or nake [ground wire ] will go to one piece of equipment and the other set left will go to the other. DON'T FORGET TO HAVE A GROUND WIRE TO EACH. It can be green or Nake wire. If I run all three circuits in one conduit, then that's 6 conductors plus ground. Do I have to derate the conductors, and does that mean using #10 gauge THHN for a 20 amp circuit? We will have to cover the rating of the wire / breaker size by the way you run it and go by a wire chart for what you call derating the circuit or wire. I have wire charts to tell you what will fit in the conduit and what rating of the number of wire / amp draw of each / size of conduit. Tell me what way your going to run the wire like all in one or seperate conduits. If you like you can e-mail me and I can look up the wire rating verses the conduit size for you or post back here. TURTLE |
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