How much romex in 2" PVC conduit from 1st floor to 2nd floor?

Discussion in 'Electrical Forum discussion & Blog' started by Steve Zerby, Jun 13, 2013.

  1. Steve Zerby

    Steve Zerby Remodel Contractor

    Messages:
    12
    Location:
    Upstate NY
    Years ago I ran a 2" PVC conduit from my electrical panel on the first floor up to my unfinished second floor when I closed the wall that the panel on the first floor is recessed into because I wasn't going to get around to building out the second floor for some time.

    That time is now.

    the second floor specs:

    1700 sf
    two bedrooms
    two bathrooms
    about 800 sf greatroom
    storage loft over the bedrooms
    future plans for a darkroom

    I was planning on just pulling whatever individual romex runs I needed to complete the second floor wiring, but am wondering how many romex cables I can put in a 2" conduit. The fill tables say 99 conductors for 2" conduit, but I know that is loose wires, not romex.

    I was figuring on:

    (2) 12/2 for the bathroom GFI circuits

    (4) 12/3 wires for eight additional general purpose circuits:

    (2) outlet runs for the great room (a/b)
    (1) outlet run for the two bedrooms
    (1) lighting run for the great room
    (1) lighting run for the bedrooms and bathrooms
    three extra circuits for future use

    It's a straight run up of only about 6 feet in the conduit till I'm into open wall again. Most of the romex runs would exit the conduit there, but one or two of them would continue on up to the loft area through another 10 feet of conduit for future use. I could still pull wires from the panel through the conduit to the loft area if needed in the future as well.

    Is this a decent plan, or should I put a subpanel upstairs instead? I hesitate on the subpanel, because I don't want to ugly up the living spaces with it. I could put it in the loft, but that is going to be accessible only by a pull-down stairs or ladder of some sort, so will be a pain when I'm old(er).

    What do you think?

    Thanks,

    Steve
    Last edited: Jun 14, 2013
  2. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    There is an issue beyond fill: there is a limit on how many "current carrying conductors" you can have in the same raceway (conduit) assuming it is over 2' long.

    If the insulation is rated below 90 degree centigrade, the limit is three current carrying conductors.

    For thhn or thwn, the rating of the insulation is 90 degrees, and the limit goes up to six conductors.

    If you need more than that, one gets into derating calculations, and the ambient air temp that the raceway is in is also calculated. It can get quite convoluted.

    All that said, I have never considered the matter with NM.

    You are running a lot more circuits than needed, I think. You only need one dedicated 20 amp circuit for all the bathroom outlets, but they should serve no other purposes. Some will say you can hang bath lights and fans on them, I'm not so sure.

    Mike Holt has a free calculator if you go to his site: http://www.mikeholt.com/freestuff-menu.php look at "residential load calculators".

    A sub panel is a VERY GOOD idea. Do not put it in a closet or a bathroom. Put it behind a bedroom door where it will not be on view very often. You need two hots, a neutral and a ground. The ground can generally be one size down from the hots. Don't forget to keep the neutral and the ground separate in the subpanel. And the hots must be correct colors, the neutral must be white and the ground must be green.

    You can get non metalic in 6-3, although it will cost a fair bit. It would be just the thing to fish up your plastic conduit, just treat it as you would any NM when it passes thru a stud.

    As for general purpose circuits, I am just a tyrant against making them 20 amp and using 12 ga.

    There is NO reason to do so nor any advantage. 15 amp with 14 ga is perfectly adequate and lord is it a lot easier to stuff the wires into the boxes.
    Last edited: Jun 13, 2013
  3. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,248
    Location:
    Land of Cheese
    Our inspection dept does not allow NM cable to be ran inside of conduit, except for short runs where it is done as protection from physical damage. I think this was discussed here before and the jury was still out. Essentially, NM is not rated for use in conduit, so good luck finding any fill or de-rating guidelines to do so.
  4. Steve Zerby

    Steve Zerby Remodel Contractor

    Messages:
    12
    Location:
    Upstate NY
    A couple of questions:

    Can you have a door swing into the 3-foot access area for a subpanel?

    What is the rationale for not allowing romex in a raceway? Heat?

    I always run nothing but 12 ga. Overkill, I know, but I would rather have too much capacity than not enough. It'
    s not about what's easy, it's about what serves my needs best.
    Last edited: Jun 14, 2013
  5. Steve Zerby

    Steve Zerby Remodel Contractor

    Messages:
    12
    Location:
    Upstate NY
    I did a little searching around the web before posting here, and my interpretation was that in the absence of some local amendment, NEC does not prohibit it. Is this a cheese-land thing? (asked the ex-land-o-laker)
  6. Steve Zerby

    Steve Zerby Remodel Contractor

    Messages:
    12
    Location:
    Upstate NY
    I believe I need a 20-amp circuit for each of the bathrooms. Even if I don't NEED them, I think it's still a good idea. What if both bathrooms are in use at the same time and a hair dryer is in use in each one at the same time? I personally think it's fine to have the lights on the same circuit, but why not throw them off to another lighting circuit just to keep the codes office happy.

    I know I tend towards overkill on the outlet circuits. But I'm a big fan of big TVs, computers and such.

    Steve
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,684
    Location:
    Cave Creek, Arizona
    wire

    quote; You need two hots, a neutral and a ground. But NOT just "any" two hots. They have to be on opposite poles of the power panel so the sub panel is being fed with 240v power. IF he used two hots from the same leg, the neutral would be overloaded.
  8. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    If you are sold on “overkill” then install a remote panel on the second floor and feed everything out of that panel. Install a 90 amp breaker in the main panel and install #2 SE-R to the remote panel. Then you will have enough to power a big TV in every room and computers also.

    Yes you can install NM-B in conduit but derating takes place the second more than three current carrying conductors are installed in that raceway.
  9. Steve Zerby

    Steve Zerby Remodel Contractor

    Messages:
    12
    Location:
    Upstate NY
    That's the direction I seem to be headed in.
  10. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Right you are. Never assume anything. Spell it all out.

    Still, if he is going to feed the sub panel off of a two pole breaker, he'd have a hard time doing anything other that the right thing.
  11. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    A 100 amp panel with a 90 amp service from the main will MORE than service your 1700 second floor. The AC is on the main panel? The kitchen as well? The laundry? The charger for your electric car?

    You will be well served.

    15 amp circuits are safer than 20 amp. Try to get JW to explain it to you, he is better at it than me.

    You should have no issues running the cable up the conduit, to my mind, but there is no reason not to talk to your inspector first.

    I admit to being spoiled by my local inspectors, who, if you know when to catch them and don't ask absurdly stupid questions, are happy to help.

    I want to hope that your guys are similar in their attitude.
  12. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    You may indeed. What is required is that you have a 3' sq to work in. The door swinging over it is not a problem. Don't put it in a closet or the bathroom.

    You got me. My understanding is that you can certainly put up to three conductors (12-3, etc) without any problem. It would certainly be a heat thing, but that is the whole point of three conductors, you don't get induction, and if it were metal conduit, that would flatten off the induction even more.

    14 ga 15 amp is cheaper, quicker, easier, and safer. What is not to love?

    The requirement for general lighting circuits is 3 voltamps per sq ft.. The formula is 3 va times sqft all divided by 120(volts), which renders how may amps you need to be prepared to deliver. Assuming 1700sqft the result is 42.5 amps. Divide that by 20 (amps) and you get 2.13, meaning that you can almost get the job done with two 20 amp circuits. Divide by 15 (amps) and you shoot all the way up to 2.83 circuits being required. In both cases you are required to install three circuits. Instead, install four 15 amp circuits in your 1700 sq feet: you have ample wattage per sq ft. 60 amps when the minimum is 42.5 amps. I cannot imagine what in gawds green earth you think you are doing up there that demands more.

    And more smaller circuits (within limits) are better, because less of the area would go dark if a circuit breaker trips.

    But do run a demand calculation. How many massive TV's drawing how much power do you actually intend to install?

    Me? I'd always run one more 15 amp circuit before I ran 20 amp circuits.

    I'm nearly sure that four 15 amp circuits will serve you handsomely.

    Oh, any heat for the bathrooms? Circuits for those.
    Last edited: Jun 16, 2013
  13. Steve Zerby

    Steve Zerby Remodel Contractor

    Messages:
    12
    Location:
    Upstate NY
    I have my reasons. First off, I need two 20 amp circuits by code...one for the GFI in each bathroom. I need more than one lighting circuit, as you say, so that the whole floor doesn't go dark. That's two more. The great room will probably have a lot of fairly strong indirect lights and recessed cans. Until recently it was pretty easy to max out a twenty amp circuit with a bunch of halogens in a bunch of 4" cans. Indirect lighting can take a lot of wattage pretty fast too. I'm also an ex-professional photographer and may use the great room as a studio from time to time. That can introduce some pretty heavy lighting demands too. It's also likely to have a mega-TV/entertainment center. So I want two twenty-amp outlet runs in there.

    The lighting circuit for the bedrooms and bathrooms will have bath fans, and maybe some light/heat units as well.

    I assume that any bedroom could someday be a teenage boy's castle, with heavy duty TV, computer, stereo, maybe an electric guitar, and god knows what else twenty or thirty years from now.

    Also, I'm now a general contractor and any outlet has to be ready for a heavy draw wherever I might want to plug some big honkin' tool in;-)

    Anyway, when I close this wall, I won't have acces to the main panel anymore, so I want to leave my options for future expansion open. That's why I'm leaning toward a 90 amp sub panel. What if I want to add a large addition? Or go up another story?

    I like to leave my options open.

    I can see the lighting circuit that isn't the great room being 14-amps, but why bother for just one circuit?

    Like I say, it's not about what's cheap or easy. Never has been for me. It's about what serves my needs.

    Steve
    Last edited: Jun 16, 2013
  14. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    OK, first you have me confused. And then I see you are confused.

    How in the world are you going to put a third story on the structure? Your foundation is strong enough? The first floor can take it? Or is this all some dream that imagines you will dig out under your foundations and make them deeper and wider to take the load? I have never heard of such planning.

    Regarding the electrics. Yes. By all means. Put a big sub panel up there. I suggested that way up the page.

    You are drastically incorrect regarding the number of circuits you must install for general lighting. The circuit(s) for bath outlets have nothing to do with it and are not in the count. Nor are any circuits to power heating units of any sort. Those should be dedicated circuits.

    Look at my calculations. You need to put in three branch circuits, of either 15 or 20 amp. And what in the heck kind of power tool do you think you are going to plug in in the middle of your house that will not run on a 15 amp circuit? Are you going to be welding while the kids play Nintendo?

    BTW, you should definitely be looking into LED lighting for new construction. Seriously.

    Code requires that you provide 42.5 amps of capacity on the general lighting circuits. You cannot round down. Two 20 amp circuits will not do it, and they have nothing to do with the bath plugs.

    You can put in three 20 amp circuits and have a substantial surplus over your requirement. You can put in three 15 amp circuits and have a small margin over minimum. Or you can put in four 15s and have again, a substantial surplus.

    Four 15s, assuming the panel is reasonably centrally located, will be cheaper, quicker, easier, and SAFER than would three 20 amp.
  15. Steve Zerby

    Steve Zerby Remodel Contractor

    Messages:
    12
    Location:
    Upstate NY
    Don't make assumptions. When you do you just...well, you know the rest...

    This is an almost 200 year old timberframe structure that I've been working on in dribs and drabs for the last 20 years. I was being tounge-in-cheek when I said I might go up another story, but the upstairs is 12 feet to the rafter plate, and 20 feet to the peak wtih a cathedral ceiling. I am putting a loft above the bedrooms and bathrooms. The original foundation is two feet thick. The soil here is excessively boney, and I could pile another one of two of these buildings on top of this on and the foundation would be just fine. I do plan to add a dining room wing sometime down the road, that would be easier to feed from this new sub-panel which will still be accessible when the time comes

    We are saying the same thing, just not understanding each other. I plan on two dedicated circuits for the two bathrooms' GFIs and two or three general lighting circuits. The only place we differ is that I plan to run three circuits of 20 amps for outlets: one for the two bedrooms, and an a/b pair of circuits for the great room because I may have heavy usage requirements for it at times.

    I have plenty of hand power tools that draw 13 amps alone.

    I am. I've been swapping everything out for LEDs as I buy new bulbs now. I expect everything up her will be LED.

    As I said, we are really not very far apart here.

    Thanks for your input.
  16. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Just to emphasize, you do not have a choice, assuming you actually do have 1700 sq ft as you initially indicated.

    You must put in three branch circuits, not two.

    Regarding the 13 amp tools, and I'm an electrical contractor, I have a few big tools, how many are you going to be using at once?

    This is a point I run into all the time, both here and in my real world: some guy wants power in his garage, and he is thinking of a 50 amp or some guys even want 100 amp panels.

    Good lord. Not that I mind taking their money, but really. 6 ga when 10 ga will do? "But I have so many tools!" Yes. How many of them can you use all at the same time and not cut your arm off?

    And you could have just written "Oh, should have mentioned, the first floor is not modern construction, but is a very old and sturdy structure" rather than taking a 'tude about it.

    Use 12 ga if you insist. It is not as safe as 15 amp circuits.
  17. bluebinky

    bluebinky Member

    Messages:
    397
    Location:
    Santa Clara, CA
    A few milliamps can kill and a 12A load is max for a 15A circuit. Where's the data that shows a properly installed 15A circuit is safer?

    I'd run #12 with (some 15A breakers. Forget about the high cost of copper, it's the AFCI breakers, if they are required (yet) in your area that will break the bank.

    By code, one 20A fine for running just the wall outlets in both baths. However, forget using two hair dryers, etc...

    As for tools in a shop one could run these together:
    - 2 hp table saw
    - dust collector
    - air compressor (could start)
    - air conditioner
    - lights
    - TV

    May not be more than 50A, but getting close. Add to that several hundred feet of undersized feed from the main panel and the lights start to dim... The cost of a 100A vs a 50A panel is nothing compared to the installation costs...
  18. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    You want to go to JW for the details on why 15 general load circuits are better than 20 amp. He explains it much better than I do.

    Granted, one could have all that in a garage half a mile from the house, I suppose. Here in Los Angeles we tend to have our out-buildings ten or twenty feet from the main house, dirt is expensive here. And yes, if you are trenching 18" deep for half a mile, you may as well drop in more conduit and wire, why not?

    But here a 30 amp sub is enough. 50 is More than enough.

    Meanwhile, general use circuits in a home need not be more than 15 amp. If I decided to deliver 60 amps to a 1700 sqft house, I would use four 15 amp circuits, rather than three. Much better. Especially if the panel is reasonably centrally located, no more expensive. Cheaper even.
  19. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    There is a big difference between 600 watts of heat on a small appliance cord such as a table lamp or clock plugged into a 20 amp circuit verses a 15 amp circuit.

    The old adage that larger is better is nothing short of a depletion of our natural researches (copper).

    We must remember that it is the fuse or breaker that is protecting everything down stream so to try to protect a table lamp or a clock with a 20 amp circuit verses a 15 amp circuit is to allow at the very least 600 more watts of heat to pass the breaker or fuse.

    If it is a breaker then as a general rule of thumb the trip curve of the breaker is six times the rating of the device. A 15 amp breaker will open in .033 seconds at 90 amps but a 20 amp breaker will allow 120 amps flow for the same amount of time.

    Knowing this, in the event of a ground fault at the appliance cord or future downstream a total of 3600 more watts of heat will be allowed to pass through this small cord. This is the amount of heat of a small burner of an electric range.

    Yes on a general lighting circuit a 15 amp breaker is far safer than a 20 amp overcurrent device. Instead of installing a larger circuit in order to plug in more appliances it would be far safer to install two smaller circuits for the same amount of load.

    Installing a 20 amp circuit and 15 amp receptacles does nothing for the receptacle which is only allowed to be loaded to 12 amps. Should someone plug two 12 amp appliances into 15 amp receptacle then the 20 amp breaker would be overloaded so what is gained by installing and wasting all that copper?
  20. Steve Zerby

    Steve Zerby Remodel Contractor

    Messages:
    12
    Location:
    Upstate NY
    Well I'm definitely learning things here. This is a marvelous forum. I am taking all of the information to heart.

    Sorry if I developed some attitude, but this passage just set me off a little:

    It seemed to presume that I don't know what I'm doing as a contractor.

    One of the things that has made me tend toward more rather than less and bigger rather than smaller circuits is the history of ever-growing electrical consumption in this country. I am mostly a restoration contractor working on buildings from the mid nineteenth century. I can't tell you how many places I've had to work on that had completely inadequate electrics. I'm sure the electrician that put an outlet in every room and a 60-amp panel with four fuses for the whole house thought it was more than anyone would ever need.

    In these older houses it is often impossible for me to run a skilsaw and and anything else at the same time (dust-collecting vac, halogen work lights, compressor plugged in and happens to kick on while I'm making a cut on the chop saw, etc, etc.) I've made far too many trips to the fuse panel. And virtually every tool I use now has to be connected to a dust-collecting HEPA vac for the lead paint rules.

    LED lighting is the greatest thing since sliced bread!

    Now if only they could make electric motors as efficient.
    Last edited: Jun 18, 2013
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