I live in a ranch house with a full unfinished drive-out basement. My breaker panel is at one end, and my garage/workshop is at the other. I would like to run romex through a conduit fastened to the underside of the floor joists to power a few more outlets. I know I will want some 110 and some 220, but I’m not 100% sure how many of each. There are plenty of slots left in my main panel. The circuits would be for woodworking type equipment, dust collector, table saw, air compressor, that kind of thing.
I have no intentions of digging into the breaker box, I’ll leave that to the pros. But I would like to hang the conduit and pull the wires myself. Several questions: 1) If I wanted to have say two 220 circuits and three 110 circuits, how big of a conduit would I need? 2) What size romex should I run? Can I pull 10-3 cable for each circuit and be covered? 3) Anything else I should keep in mind?
Thanks for any info you can give me. I know how well amateur electrical questions go over sometimes, so be gentle.
Bart
Replies
What you want to do is install a subpanel in the workshop area. I would not recomend pulling multiple new circuits from the main panel. Pull one cable from the main panel to the subpanel. Backfeed a breaker in the subpanel for the main. You will need a hold down kit for the new main breaker. Then install branch circuits in the subpanel. You will need to consider what equipment you are running in the shop to determine your amperage needed. If you do a 50 amp feeder I think you need 6 gauge wire. Check with your inspector on grounding. Often you will need to install new ground rods to serve the subpanel.
This is an old post, so I'll just hope you're still there, Akela. I'm running a 100 A subpanel to a basement workshop. Ran about 100' of 2/3 w/g, copper. I have a panel to use which does not have a main breaker, and thought about putting a 100A breaker in it and backfeeding the rest. Of course this will come off a 100A breaker in the panel. What do you mean by a "hold down kit"? Since this is a four wire set up in one building (i.e., separated "floating" neutral, separate equipment ground) I don't intend to have driven grounds at the sub-panel. See any problems with that? Thanks for any help.
Being a subpanel you need four-wire cable (H-H-N-G) if you intend to have a neutral, any 120v circuits run from this panel. If this subpanel feeds nothing but 240v loads, like a range and a 240v AC unit there is no need for a neutral conductor and three wire (H-H-G) will work fine.
The other possibility for a subpanel is to use three wire cable and to install only one leg. (H-N-G) This would be a 120v only situation as there would be no second leg from which to derive your 240v.
I usually run four-wire because in the normal turn of events someone will want to add a 120v circuit from a 240v only (H-H-G) panel or a 240v circuit from the 120v only (H-N-G) panel. Lacking a neutral, or second leg, a hack will switch around the feed conductors so that the neutral and grounds are combined and go to the other end and attach the ground to the neutral. You end up with (H-H-N/G) which is fine for the first point of disconnect but a potential safety hazard anywhere else.
Neutral and grounds need to be segregated at this subpanel by use of an insulated neutral bar. Most modern panels come with one of these installed at the factory. In the case of a service and the panel being the first point of disconnect a screw is driven into the insulated neutral bar or a jumper added to electrically connect the neutral to the ground. This must only be done at the first point of disconnect.
The ground is typically bonded to the steel panel box, enclosure. The ground rod is optional in this case, a subpanel within the same building but adding a ground rod will not substitute for a ground wire in the feed cable.
In this case you are coming off a panel to feed you sub panel. To make the connection/s to the bus bars in the sub you are back feeding a two-pole breaker. Fair enough. In this case you need a 'hold down kit', usually a plastic clip or a long screw and washer. These are designed to mechanically lock the back-fed breaker into position. The idea being that breakers, some designs more than others, come out rather easily. Sometimes, especially if connected to larger and stiffer conductors, on their own.
This wouldn't be too much of an issue with a breaker fed fro the bus bar. If it comes loose when the panel cover is removed what comes out at you is electrically dead. This is not the case with a back fed breaker. If it comes out of the box when you remove the cover your looking at a 240v stinger. The hold downs are designed to prevent this unfriendly event from happening while still allowing the breaker to be removed for maintenance or replacement.
As always. Be safe. Do your homework. If your not dead sure what what your doing a professional electrician is a bargain compared to an ambulance ride or a visit by the fire department.
4Lorn1,
Thanks, I get the issue about the back fed breaker pop-out problem, and will get the appropriate hold down to secure it. I have already run the feeder, which is HHNG and will have segregated N/G in the panel.
My next question (I'll do another post) has to do with fastening device boxes to steel lolly columns. This subpanel is going in a new basement, where I'll have a shop with 120v and 240v equipment (table saw, dust collector, planer, jointer will all be 240, maybe some other items -- e.g., band saw). I'm going to run a bunch of outlets around the perimeter, including a couple of 120 circuits and a couple of 240 circuits for outlet/plug connections. I'd also like to put some on the central lolly columns in the basement, which are steel, concrete filled. My thought was to run EMT up the columns into the joist work, there picking up romex feeds to run down the EMT into a box. Run two screws into the column (after a lot of drilling) and also fasten the EMT straps into the column. Any thoughts?
As I understand it lally columns are typically mild steel filled with concrete. Commercial high security door frames are similar in make up. I have had some luck drilling these by center punching and using a sharp carbide. I use short Tapcons and drill the steel oversized. For 3/16" Tapcons I used a 1/4" masonry bit.
Once through the steel I switched to a 3/16" bit, or the bit properly sized for the size of concrete screw you use, This has the screw gripping the concrete rather than getting bound up in the steel casing.
I'm not sure how much this would weaken the column but I suspect not much, if any. In some cases I have used two or three conduit hangers sized for the column and then used bolt through the hangers to mount my boxes. The only problem is that the hangers can sometimes spin around the pipe. Where the pipe isn't carrying anything inside a small sheetmetal screw installed into a hole drilled through the hanger and into the pipe keeps everything solid.
Another option would be to use cast iron stand offs. These are designed to fit below a one hole strap and conduit to allow water to drain from behind the horizontal conduit. A standoff sized for the diameter of the lally column, or as big as you can get, could be attached by using stainless worm drive band clamp. This would leave the tapped hole exposed on the bottom of the clamp. You may need to drill these on through and tap a little as some are blind from the opposite side.
The stand off would give you a nice flat surface to run a bolt into from inside the panel or boxes you are mounting. Three or four of these units behind a panel should provide a solid mount.
The other option, my choice if I had the equipment at hand, would be to weld on a piece of channel. A piece about as tall as the panel with five or six half inch beads run in pairs across from each other would make a grand mount. Be sure to drill, transfer the holes to the panel and tap the channel before welding and plug the holes with some foil tape to keep the threads clean. Welding shouldn't take more than a minute or two with most of that spent lining up.
I have also seen people box in a column and just attach everything to the wood box. The box can be kept from spinning by running one or more pieces up onto the joists above and/or fastening an angle bracket to the floor. This would likely be strong enough.
Not sure if I answered you question but this gives you some options and even if none of these seems right they might spark some alternative ideas. Let us know how it goes.
What do you mean about putting a small sheet metal screw where the pipe "doesn't carry anything", not sure why it would be there if so? If we are talking conduit I would think that would not be a good idea or are you talking about the column? What about powder actuated fasteners to shoot the conduit straps to the column? If they will shoot into steel beams and concrete the should do it. I would temp clamp or tape them, put on the glasses and ear protection and fire away.
I threw in the 'not carrying anything' because people who otherwise would avoid doing stupid things sometimes get carried away during construction projects. I was once on a crew working in an industrial setting when one of the journeymen, I was an apprentice at the time, ran a self-drilling, self-tapping screw into a seemingly inert and abandoned piece of machinery. It turned out to be the storage tank for an ammonia refrigeration system. We had to abandon the area, actually this caused a general evacuation of the building, while the building was ventilated and repairs were made.
I was attempting to avoid interference with the thread forming mechanism in overprizing the hole in the steel. The steel tends to force the advancement of the Tapcon to exactly match the threads on the the screw. In itself this is not a problem but the same screw forming threads in the concrete tends to want to slip a bit before gripping the concrete. This differential in behavior can cause the Tapcon to bind, strip or break.
A similar behavior can be seen if you attempt to screw two pieces of wood together, through one and into another, when they are not held firmly together. This typically causes an annoying gap to open up between the two pieces as the screw takes a turn or two to penetrate the second piece of wood while still advancing through the first.
Unless you happen to like life under fire I would avoid using a powder actuated fastener. These pins tend to deflect and ricochet badly if they fail to meet the work squarely. On the cylindrical form of a lally column a minor deviation from the exact center and tangential orientation will greatly increase this effect. Making this shot while holding an electrical panel would not inspire warm, comfortable feelings. Eye protection and body armor might be a good idea.
I don't know that there would be anything wrong with using straps around the columns, if that would be simpler (and visually acceptable to you). Probably a good idea to run at least one screw into the column for the box itself, to keep it from possibly rotating, but otherwise the straps should be sufficient.
I rather imagine that this is what your garden-variety electrician would do.
> Run two screws into the column (after a lot of drilling)
If you have access to the columns before they get filled with concrete, Just drill #29 holes and tap 8-32. Use 1/8" as a pilot drill so the #29 will clean up nicely. Use cutting oil for both drill and tap. A drill press would be ideal, but a drill motor with enough oompf will do. If you get 1/4" of engagement, that's more than plenty. This is very common straightforward machine shop work. (Put screws in the holes while you pour the concrete.)
-- J.S.
Hanging the conduit and pulling the wires is no big deal for the electrictian. (Why should they trust your pulling skills to not damage the wire?)
I like the suggestion of a 50amp circuit to a sub panel.
You do not need a disconnect for the panel, but I would buy a panel with a disconnect.
Around here most electrician don't like connecting home owners wire to the service panel or to the other end. Maybe I should say will not connect a HO wire to the service. They claim insurance won't let them do it.
What if I said the pro would be my father-in-law? I hear what you guys are saying about the subpanel, that probably would be the most proper way to go. But assuming that the individual circuit wires are properly pulled, not damaged, and correctly connected, what would be wrong with running them through conduit? It's a small house, so we're not talking about miles worth of wire strung through the basement.
If that would be bad or illegal or just dangerous for some reason, I won't do it. Maybe I'm wrong, but when you start talking about 6 gage wire and subpanels and disconnects and additional grounding, I start seeing $$$$$. All I'm really trying to achieve is a dedicated circuit for my air compressor, a couple of more outlets for my stationary equipment, and maybe one or two for future expansion. It is certainly not something I would want to drop big bucks on if there is an acceptable alternative.
Thanks for the advice so far, I'm looking forward to hearing anything else you guys have to add.
Ditto on Chuck and Dave's comments.
Bart,
each circuit would need one each of hot, neutral and ground for 110v,
two hot legs, one neutral, and potentially a dedicated ground for most 220v. I'd wire not less than 12 ga., with 10 ga. used for Heavy Duty items with motors at or over 3 HP. Given the cost of THHN/THHW, conduit, fittings, and junction boxes; it
may be cost-effective to pull one 6-3CU-w/ground and mount a 50A - 6 space subpanel. (Assumption of approximate 50 foot run.)
USE COPPER conductor Romex. You'd then use standard romex 12-2 or 12-3 for your outlets, wired from the subpanel.
The Romex Feed Line, plus the subpanel with breakers should run under $200 at most supply stores or big-box outlets.
Your relative might get a better deal at a Supply House.
None of this is rocket-science, but I'd get Pop's advice before doing
something he's uncomfortable with.
-GWC
PS: Don't go messing inside the meter socket... if you think there's too much electricity inside the panel... see those two prongy-things up top? They connect to the transformer on the pole by those other wires coming to your house. Z-Z-Z-ZAP!
"each circuit would need one each of hot, neutral and ground for 110v, two hot legs, one neutral, and potentially a dedicated ground for most 220v.
I don't want to start anything but please tell me you had a brain fart when you typed that.Who Dares Wins.
"each circuit would need one each of hot, neutral and ground for 110v, two hot legs, one neutral, and potentially a dedicated ground for most 220v.
Gunner, I don't smell anything.
What's wrong with that?
SamT (once was a 'tronics tech)
I should have narrowed it down farther.
"two hot legs, one neutral, and potentially a dedicated ground for most 220v."
Eh Eh! You don't use a neutral for 220. That's basic knowledge. Who Dares Wins.
And a dedicated ground for ALL 240 (and 120).
DUH
Gunner,
are we talking to a pro, or to a DIY who needs to think "white to white", "copper to copper", "black to black" and "red to red"?
Now, I'll wait for you to explain how blue, yellow, orange, etc... are all valid colors for hot leg circuits, how brown and black are used for different purposes in DC wiring, etc....
With newer 240v Dedicated Equipment Ground installations, indicating that white is the same as copper/green may not have done this fellow any favors.
Of course, dedicated ground service should be used with appropriate panel configurations, similar to hospital-grade isolated ground applications, or we're just smoking our shorts.
-GWC
If the pro is your Father in Law, maybe you could let him supervise the conduit work. The Electrical Code specifies how many wires you can put in a given sized conduit. And it's goverened by gauge which is determined by the amperage of your circuits as opposed to the voltage. That said, conduit is relatively cheap. Larger conduit will hold more wire and the wire will be easier to pull. Make sure you ream the ends of the conduit so a burr or sharp spot won't peel the insulation off the wire when you pull it. PS, It is my understanding that romex should not be put in conduit. I agree with the other post that says the conduit work isn't a big deal for an electrician. Doing the conduit and leaving the rest to him might not be saving you any money in the long run.
As Chuck pointed out, Romex doesn't go in conduit. Insulated wires like THHN, THWN, etc in the appropriate gauge go in conduit. Romex goes through the studs (with enough wood around it or with nail plates) and through the bays between studs.
Whether you can use PVC electrical conduit versus thinwall EMT is a local question. Ask your building department.
I'm always puzzled by the "I won't go inside the panel" mentality in DIYers and in prospective employees (that I don't hire). There are the same electrons in a distribution panel as in a duplex receptacle or a 4" round for a ceiling light. Plenty of voltages and amps in either to kill you. It's always seemed to me that either you 1) turn off all the power or 2) be comfortable and extremely compentent at hot work or don't do electrical work. Why distinguish little wires from big wires? A 15-amp breaker is not going to save your heartbeat. Knowledge and proper work habits will.
David Thomas Overlooking Cook Inlet in Kenai, Alaska
I guess my concern with doing work in the panel is that unless you pull the meter there is still juice north of the main disconnect, right? That's a little too close for this noob. I've never pulled a meter and I wouldn't even hazard a guess as to how to go about it. Working on an outlet or a light I can throw the breaker, double-check that the wires aren't hot, and do my work knowing that there isn't a volt to be found for yards instead of inches.
Thanks for the info on romex, I obviously didn't know that. Just out of curiosity why is romex unnaceptable in conduit? Are the THHN and THWN wires you're talking about bundled into 2 or 3 conductor cables like romex, or are they just individual conductors that you label and pull?
As for having supervision on the conduit work, probably wouldn't hurt. I'm aware of the concerns about damaging insulation, but it's always good to have a second set of eyes.
I will check with the building dept Monday for specifics in my area, but are there any general guidelines on how many conductors in a given size of conduit?
Thanks again.
"unless you pull the meter there is still juice north of the main disconnect, right?"
True. If you don't like two different phases of 120 volts on those aluminium lugs remaining exposed, cut out a piece of cardboard the width of the panel and a bit higher than those lugs. Slip it in behind the lip of the panel after shutting off the main breaker. Now the only live bits are covered up and the two busses (where you'll be plugging in new breakers) are de-energized.
why not romex in conduit?
It is too hard to pull. Three or four solid conductors, insulated and then further wrapped/insulated with the outer grey layer? Several of those? That is a lot harder to pull than 3 or 4 THHN of the same gauge. Even when you stay with the number of conductors limit and do not exceed five 90s and use stranded instead of solid and use the gorilla snot slimey pulling compound, it gets really hard to pull anything close to the limit. There may also be heat dissappition issue but I'm not sure - you can spray-in-place foam right over romex and that's gotta retain heat more than a conduit.David Thomas Overlooking Cook Inlet in Kenai, Alaska
Great tip on the box guard, thanks. I'll give that a real close look to see if that would give me enough of a warm fuzzy feeling to get in there. I usually work on the priciple that if it makes me nervous, I probably shouldn't do it.
I'm going to check with the local officials Monday about whether romex is allowed in conduit, what kind of conduit is required, etc. But the run I'm talking about is a single straight shot, and I can use as big a conduits as I need to make the pulling easy. Check that, there will be one 90 degree elbow to run one of the circuits out of the conduit and down a support column before the end of the run. But one circuit/cable/set of THHN wires wouldn't be a problem, right?
While I'm asking questions, what is the difference between plastic conduit and other rigid plastic pipe like PVC? Different strength requirements?
The NEC allows Romex in conduit. Not usually done, however, because with the diameter assumptions you are required to make, you'll run into conduit fill restrictions. (Without getting bogged down in details, you would have to measure the width of the romex with it lying flat, and treat it as a single conductor with that diameter. see Chapter 9, Table 1, note 9 of the NEC (99 edition, anyway)).
THHN wires bundled into one conductor is exacty what romex is !
For conduit fill, here's one example (out of an infinite number of possiblilities): in half-inch EMT, you can pull 9 THHN 12 AWG conductors or 12 THHN 14 AWG conductors (NEC Appendix C). That's the conduit fill restriction - as others have noted, amperage derating may apply).
I just reread you original post. If I understand you correctly ("unfinished"), you might be better off forgetting conduit. Get a right angle drill and bore 3 or 4 sets of holes through the open floor joist bays, then pull romex. Even if you have to move insulation out of the way and put it back, that's the fastest and simplest way.
Edited 11/7/2003 8:31:41 PM ET by r
Edited 11/7/2003 8:38:07 PM ET by r
I guess I was thinking of three reasons for running the wire in conduit as opposed to drilling through the joists. One, part of the run will be over top of what I use as a woodshop. Even tucked up halfway through the depth of the joists, I'd be worried about swinging a piece of wood and snagging a wire. Two, to add four new circuits would mean drilling four holes in each joist. I understand that the strength impact is minimized by drilling through the neutral axis, but it would still bother me. Three, the wires will run all the way from one end of the house to the other. So maybe four holes per joist, multiplied by every single joist in the place, and you're talking about a lot of holes. Compare that to fastening up a piece of 2" conduit (just pulling that number out of the air) to the bottom of the joists with straps, seems like that would be a hundred times faster.
Does any of that make sense or am I way off track?
And a practical question about the THHN conductors--if you run 12 loose conductors through a conduit to feed four circuits, how do you keep track of which are which? Label each wire at both ends before pulling? Probably a dumb@ss question, but I've only ever worked with Romex.
I think the impact of small holes (say 3/4" spaced 3 inches apart) in the center of floor joists is completely inconsequential. Maybe an engineer could comment. (The IRC allows holes in joists up to 1/3 the depth of the joist - for a 2 X 10 you could drill a 3" diameter hole !). As for "just fastening up a piece of 2" conduit", yes, that goes fast, but if you are pulling individual conductors, they have to be protected in conduit all the way from the main service panel to the receptacle boxes, so you'll be buying fittings, bending EMT, gluing PVC, or whatever. (Or, terminate the conduit in a junction box, and tie into romex, etc.) I think with a good right angle drill and auger bit, your 4 holes per joist could be done in less than a minute per joist. Maybe screw up a sheet or two of plywood over the shop ceiling area to protect the romex ?
THHN comes in a bunch of colors, but labelling each end works also.
OK: another idea: fasten four 1" conduits to the bottom of the floor joists from one end of the basement to the other. then pull 1 romex cable thru each. You won't have to derate since only 2 current carrying conductors in each conduit. Fasten the romex to the studs with cable staples. (But I still favor the drill, auger bit, and a sheet or 2 of plywood).
David -
It is my understanding (as a non-electrician) that under the latest code, non-metallic sheathed cable, types NM, NMC, and NMS, can be protected by conduit. I think one of our Breaktime electricians mentioned this some time ago. In the past, I believe it was felt that running Romex type cable in conduit posed a problem of heat build-up. I think one still needs to be cognisant of fill and temperature requirements, but it appears that running it in conduit is not only allowed but recommended in certain situations. In 334.15 of my abbreviated Pocket Guide to the 2002 NEC, "the cable shall be protected from physical damage where necessary by conduit, electrical metalic tubing, Schedule 80 PVC...." The section goes to proscribe "when running through a floor the cable shall be enclosed in rigid metal conduit, intermediate metal conduit, ..." etc. It states that the non-metallic sheathed cable shall be protected when going through the floor for at least 150mm above the floor. It doesn't list a maximum length for such protection that I see.
Hopefully, someone actually qualified will comment on my above statement...
As others have suggested, it may be best to have your father-in-law advise you on what to do - this isn't a real difficult thing to do, but there are a lot of unknowns we can't see from here that make it difficult to give you any good answers.
In general terms, assuming your house isn't really long (so you don't have to worry about voltage drop,) you can use 14 gauge wire for 15 amp circuits, 12 gauge for 20 amps, and 10 gauge for 30 amps. However, if you run more than a couple circuits in a single conduit, the electrical code de-rates the current carrying capacity of the wire and you have to use a larger gauge.
And, there are some issues with how the conduit is installed - for instance, you can have only so many bends or elbows in a single run before you need a junction box. It may be easier to install several runs of smaller conduit than a single large conduit, too.
Finally, since this is a home shop I assume it will be mainly just you working there, so you may not need very many circuits (since you can only use one power tool at a time, the actual current load at any given time probably won't be that high.)
Subpanel is the best way to go. One mistake you are already making is worrying about cost when dealing with electricity. Trust me spend a little more now and be happy the rest of your days.
If you insist on doing it the hard way run a "future use" conduit next to your new one. Then if you come up with something else you want to add later, it's just a matter of pulling it in. And an empty conduit is much easier to pull in then one with wires already in it. Trust me I've pulled miles in both all week.
As far as worrying about how much you can put in your conduit you have to figure out what you want in it. Then look it up, the uglies manual is my favorite but there's plenty of other sources around. And I also think pulling romex in a conduit is a waste of space.
Who Dares Wins.
Someday I hope to not have to worry about cost, but for right now it is still something I have to think about. But you are right about the subpanel, I'll get a few prices this week and see what that is going to look like. If it isn't a whole lot more that's what I'll do. My biggest worry about that route is what someone said earlier about needing to install new grounding rods. There really isn't anyplace on the subpanel end of the house for grounding rods, the driveway buts right up against the house.
So when you install a subpanel, do you feed it off of a breaker in the main panel? Would it be like a normal 220 breaker, or something else?
"So when you install a subpanel, do you feed it off of a breaker in the main panel? Would it be like a normal 220 breaker, or something else?"
Yes you feed it off a normal 220 breaker in your main panel.
Who Dares Wins.
" "So when you install a subpanel, do you feed it off of a breaker in the main panel? Would it be like a normal 220 breaker, or something else?" "
"Yes you feed it off a normal 220 breaker in your main panel."
Gunner,
Don't you get the feeling from a question like that, that maybe, just maybe, it's time to suggest calling in a pro?,,,,Or suggest to the DIY to do a little reading up on the topic vs. posting on BT?
Jon
His FIL the pro is going to do the hookups for him.Who Dares Wins.
"His FIL the pro"
Gunner,
Sometimes we try to read into these threads a little, looking for red flags. If the FIL is a "pro ?electrician?" why is Bart asking some of the questions he is here? I don't think that we should shy away from answering questions, but there are certain area's that novices shouldn't delve. If the FIL has offered to help, and is a "pro", why not have him do the whole (relatively simple and quick for a pro to do ) job with Bart being there as a helping hand? and a few beers and steak dinner with the Mrs at the end of the project?
Nothing wrong with people asking almost anything here, but if for example, I saw somebody post a question about which wires were hot ground and neutral, and aren't neutral and ground really the same, knowing that they were planning on a major rewire, I personally wouldn't just answer them and send them on their way.
The consensus here is that a subpanel is the way to go. But when the guy (Bart) starts asking about breakers and hooking it up, those questions are best answers with a reference book, not an anonymous screen name on the internet.
Jon
I'm taking his word for it.
I don't get involved in a lot of threads here for this very reason. In fact I don't even look at a lot of threads for this very reason. The guy tells me his FIL is a pro so I'm taking his word on it. If I was going to do my son in law a favor like this and he was willing to run the conduit I would let him. I would inspect it before I hooked anything up but I would definatly let him do all the work. The faster I can get in and out and on to my own interests the better. The guy has already said he's not going into the panel, so don't worry about it. He's just curious how it works.Who Dares Wins.
Interesting that we used the same language in our simultaneous posts. My long lost brother!
Since you have untill Thanksgiving, see if you can find or order Electrical Code Check at a local book store or have it express shipped from Taunton Press when you order it from this web site.
If you have room in your main panel for the additional circuits, you don't need to add a subpanel. Figure out the number of circuites you need, the lenght of the wire runs, conduite fill, anpacity derating, and so forth. Run your conduite to a large j-box and branch the indivdual conduite to recepticals from there. A 9x9 pull box should be big enough for all you have in mind. You can even switch froom stranded THHN to romex (type NM) at the pull box if you don't want to run conduite to each device box.
Since you have never used conduite, I reccomend pvc b/c you can buy all the fitting and bends readily at you local home center. You won't have to purchase a conduite bender and go through the learning curve and scrap pipe it will cost to do it right. Purchase a couple of pulling Cs and place them every 30 feet in your conduite run. Also buy a fish tape, wire lube, electrical tape, and a wire letter/number set.
Most of all buy the above mentioned book. Any question after you get it can be ask here, and I am sure you will get good answers.
Dave
I'm glad to see at least one other person doesn't see the merit of a subpanel. He says he has "plenty of slots" in the main service panel. The cost of another panel + the 6-3 w/ground feeder (or whatever) is way more than 3 or 4 individual runs of romex (or conduit for that matter). So if it's more money and more work, what is the attraction of a subpanel ? (I'm not buying voltage drop - nothing here indicates he lives in McMansion). As long as he has 2 slots in the main left after this project, he can always add a subpanel in the future. Or he may never need one.
Bart, I can't resist kidding you here: I think you could have drilled the holes in the joists and pulled the romex in less time than you've spent on the computer keeping up with this discussion !
94' of #12 wire will have a 5% voltage drop at 20 amps and 120 volts.
The best reason for a subpanel is that the walk to reset breakers is shorter.
I agree that it is pretty easy to get a noticeable voltage drop if you max out a circuit. (although, I get 3.5% using your example. I'll double check. You're using 47 feet of conductor out and back, correct ?)
OOps, it was past my bedtime. Meant to say 3.5 volts, not %
Edited 11/10/2003 8:59:38 AM ET by r
No. 94' out.
Well, he says it's a straight run from the panel to the other end of the basement, so you are assuming his house is over 80 feet long ? If that's correct, I'd agree that a subpanel is the way to go.
I took your 94' number to mean a 40' house or so, plus down the studs to the receptacles, so 47' out on the hot and 47' back on the neutral for a voltge drop calculation. E = (K X I X L) / CMA where E = voltage drop, K = 12 ohms per circular mil foot of copper, I = current in amps, L = total distance, and CMA = cross sectional area of the conductors. CMA for 12AWG = 6,530. So E = (12 X 20 X 94) / 6,530 = 3.5 volts The recommendation (not technically an NEC requirement) is for 3% or less, and 3% of 120 volts = 3.6 volts. So even though your assumption is that his 20 amp circuit is totally maxxed out (which it obviously shouldn't be), he's still OK.
Did I make a mistake ? How did you compute 5 volts ?
I think I used 16 amps and told you 20 amps. So your numbers are probably right. I don't know how long his house is but it is easy to get unacceptable drops in small houses.
I know in my kid's 2400sqft house the furthest sub panel is over 60' from the main. A direct circuit from the main and around a 10' square room would be over 100'.
As you said the code does not require a voltage drop check, but motore start and run easier.
...you are assuming his house is over 80 feet long ?
For calculating purposes, I have no idea exactly how long the house is. But, it's a 1500 sq ft ranch, so I'm pretty sure that it is less than 80 feet long. Definitely not a McMansion (don't I wish! Nah.)
"The best reason for a subpanel is that the walk to reset breakers is shorter."
George,
I agree completely, but they really make adding future runs a lot easier, as well as reducing voltage drop. In my modest 2400sq.ft. house I have three 60 amp subpanels (1st floor, 2nd floor, workshop) plus the 200 amp main in the basement which serves the basement (and a couple other circuits) and the subs. More expensive but I love it.
Jon
Subpanels are very nice. I wish I had used them in my current house 20 years ago.
My daughter's house (4 squares connected with short wide halls) has 4 sub panels one for each square. The main panel only has large loads, stove, electric heat, and sub panels in it.
'My daughter's house (4 squares connected with short wide halls) has 4 sub panels one for each square. The main panel only has large loads, stove, electric heat, and sub panels in it."
George,
Sounds like a duplicate of mine. And that IS the difference between Fine Homebuilding, and building just to code.
Brian P. started a thread about stuff like that (What is Fine Homebuilding?) ~ last summer. I don't recall muliple sub-panels making the list, but they sould have, if they didn't.
Jon
Bart, I can't resist kidding you here: I think you could have drilled the holes in the joists and pulled the romex in less time than you've spent on the computer keeping up with this discussion !
Perpetual waffling is my cross to bear on stuff like this, I always spend way too much time making sure I have the "perfect" solution before doing anything. Maybe that's why nothing seems to ever get done around the house...
Made a trip to the big box over the weekend and have decided to take the advice of everyone saying to go with a sub. Someone (GE maybe?) has a "workshop" package that includes a 125 amp subpanel (12 circuit I think?) and a few breakers for $40. Throw in some conduit and some wire and I'm in business.
A few more questions then. I'm not sure how to ask this, but how do I look at my main panel and determine what is the largest breaker I can use to feed the sub? Just because I have space in the main doesn't mean I can necessarily throw in a 100 amp breaker, right? I think the most I would need right now would be 60 amps to the sub, but I want to make sure that wouldn't put me over some kind of limit in the main before I start buying stuff.
With a sub capable of handling 125 amps, I need to run sufficiently large wire to handle the full 125 amp current in case someone down the line switches the breaker in the main and adds loads to the sub, right? Does anyone want to give me a clue what size wire we're talking about to do that? I will certainly double check with my inspector before doing anything but it would be nice to have some idea for the budget. And for that size wire, what size conduit should I be looking at?
I think we're zeroing in on it...
"With a sub capable of handling 125 amps, I need to run sufficiently large wire to handle the full 125 amp current in case someone down the line switches the breaker in the main and adds loads to the sub, right? Does anyone want to give me a clue what size wire we're talking about to do that? I will certainly double check with my inspector before doing anything but it would be nice to have some idea for the budget. And for that size wire, what size conduit should I be looking at?"
As far as the maximum load that you can pull from the main pannel that is determined by the demand load on the house. Go to the FHB website and look for the article on installing a new service enterance. There is a worksheet for computing demand in it. But based on the size of your house and if you have AC, electric stove, and dryer then you can probably go 60-80 amps (if you have 200 amp service).
And look at the shop loads. In most cases for home workshops, where only one person is working and only one major tools, plus dust collector, plus lighting is run at a time 60 amps is way more than enough.
Personally I would not be concerned that it was a "125 amp sub-pannel". Anyone that would arbritarily upsize a breaker based on the size of the sub without checking the size of the wire would upsize the breaker without checking the size of the sub-pannel.
Other might have different opions.
I would go with 60 amps and #6 wire. You can go bigger if you want, but I think that 60 amp is a good package for an application like this.
The main breaker in a subpanel is usually used only as a disconnect. The breaker in the main panel that feeds it limits the current.
If you have 200amp service, you can send 200amps to the sub panel if you wish.
I like using 50amp breakers in the main to feed subpanels, because I can buy those in 1/2 width.
Now you've gone and confused me, not that it's a hard thing to do. Let's say I have a 200 amp main service panel that already contains 150 amps worth of circuits (breakers). You're saying that I could add a 200 amp breaker to that main to feed a sub?
Before anyone gets in a twist, this is an academic question. I have no intentions of feeding 200 amps to my proposed subpanel.
As I said in my earlier messge, it is based on load demand. Not by adding up the amount of all of the breakers.
If you where able to load up each circuit to 15 or 20 amps, plus the dryer, stove, AC, etc you existing load would likely add up to 250 - 350 amps.
Nothing unsafe about that. The main will trip.
But you are not going to load of each and every circuit to the max, at the same time and the code reconizes this.
Part of the reason I couldn't resist kidding you is that I spend a fair amount of time in "analysis paralysis" myself.
good luck.
Brothers by different mothers. RonT. will be along shortly he claims that title with me too. He's gonna hit you up for a cut of any profits stall him as long as you can.Who Dares Wins.
He's gonna hit you up for a cut of any profits stall him as long as you can.
I'll try my best!
No worries Jon, I've already said that I have absolutely no intention of doing any work inside the panel. Some questions I ask just because I'm interested in how things work. For all I knew before I asked, the feed for a subpanel might have been split off upstream of the main. Does that mean I'm going to put on my rubber boots and dig in? No way, I'm curious but not stupid. It sounds like an ignorant question to you only because you already know the answer.
So just to reiterate, in case anyone else is worried, I am not going to make any connections at the panel myself.
As to having the FIL do the whole job, he is only going to be in town for a couple of days at Thanksgiving. We're all going to be busy with the meal and hanging out with the rest of the family, so the more I can have done ahead of time the better. I think that pullng wires through a straight piece of pipe (after having thoroughly deburred the pipe and being very careful to cause no damage to the insulation of course) should be something I can do myself. But maybe not.
Bart,
If your garage workshop is attached to the house you don't need additional ground rods.You would ground the subpanel with the equipment grounding conductor in the feeder cable,or with a separate EGC in the conduit that you would run.
Barry
That would be perfect, the garage is in the basement. Someone earlier had said that a subpanel might require separate ground rods. I'll be sure to double check that one through the local authorities just to be sure.
Speaking as an industrial electrician with 25 years experience, I would go the sub-panel route. I saw some one mentioned the de-rating factor, plus I feel it would be neater and more flexible for your shop.
Bart -
I think everyone is making this too complicated. I would run one 110V curcuit down each side and one 220V same way. Use Romex. Drill a 1-12" hole through the joists about 12" from the ends (both sides). Then put 2 (12-3 for 220v and 12-2 for 110v) wires in each hole. Plenty of room. Wherever you want a plug, drop the wire down inside a stud cavity and then back up to continue the run. If the walls are cement, drop them down in conduit. I think this would be the fastest, easiest and most economical method.
PS be sure to rent or borrow a 1/2" right angle drill for the drilling. You can drill all holes in less than an hour.
You get out of life what you put into it......minus taxes.
Marv
Don't blame me - I suggested essentially the same thing 43 messages ago ! (and use an auger bit, not a spade bit)
Marv, I'm curious why you recommend 12-3 for the 220v circuits ?
Marv, I'm curious why you recommend 12-3 for the 220v circuits ?
Well probably because I'm not an electrician. I would run it because you need two power lines, Red and Black. What's the correct wire?
Between you and me, this is a 1500 sq ft house. Not 3000sq ft. If the refrigerator was on the far wall from the breaker box, one flight up, would you run a subpanel?You get out of life what you put into it......minus taxes.
Marv
Appliances like electric dryers that need both 240 and 120 volts get 3 wire w/ground circuits. Most 240 volts tools, however, don't need 120 and thus don't need the neutral (grounded conductor). So usually they are wired with 2 wire w/ground cables. A good practise is to tape the white wire red at both ends to make it abundantly clear (or as clear as possible) to the next guy that both conductors are hots.
We are in complete agreement on the subpanel being overkill in this case with lots of slots open in the main. If you have a 3 car garage and own 2 cars, do you immediately decide you must build another garage ?
A good practise is to tape the white wire red at both ends to make it abundantly clear (or as clear as possible) to the next guy that both conductors are hots.
Thanks for the tip.You get out of life what you put into it......minus taxes.
Marv
Or, you could use the wire with the red jacket and black/red/bare conductors in it, like you use for baseboard heaters...... then everyone knows it's 220.