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

  1. #1
    Remodel Contractor Steve Zerby's Avatar
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    Default How much romex in 2" PVC conduit from 1st floor to 2nd floor?

    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 by Steve Zerby; 06-14-2013 at 04:16 AM.

  2. #2
    DIY Senior Member Homeownerinburb's Avatar
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    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 by Homeownerinburb; 06-13-2013 at 05:53 PM.

  3. #3
    Test, Don't Guess! cacher_chick's Avatar
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    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.

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    Remodel Contractor Steve Zerby's Avatar
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    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 by Steve Zerby; 06-14-2013 at 04:15 AM.

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    Remodel Contractor Steve Zerby's Avatar
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    Quote Originally Posted by cacher_chick View Post
    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.
    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)

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    Remodel Contractor Steve Zerby's Avatar
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    Quote Originally Posted by Homeownerinburb View Post
    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.
    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

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    Moderator & Master Plumber hj's Avatar
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    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.
    Licensed residential and commercial plumber

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    Electrical Contractor/Instructor jwelectric's Avatar
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    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.

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    Remodel Contractor Steve Zerby's Avatar
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    Quote Originally Posted by jwelectric View Post
    Install a 90 amp breaker in the main panel and install #2 SE-R to the remote panel.
    That's the direction I seem to be headed in.

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    DIY Senior Member Homeownerinburb's Avatar
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    Quote Originally Posted by hj View Post
    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.
    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. #11
    DIY Senior Member Homeownerinburb's Avatar
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    Quote Originally Posted by Steve Zerby View Post
    That's the direction I seem to be headed in.
    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. #12
    DIY Senior Member Homeownerinburb's Avatar
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    Quote Originally Posted by Steve Zerby View Post
    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.
    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 by Homeownerinburb; 06-16-2013 at 02:04 PM.

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    Remodel Contractor Steve Zerby's Avatar
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    Quote Originally Posted by Homeownerinburb View Post
    14 ga 15 amp is cheaper, quicker, easier, and safer. What is not to love?
    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 by Steve Zerby; 06-16-2013 at 04:18 PM.

  14. #14
    DIY Senior Member Homeownerinburb's Avatar
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    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.

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    Remodel Contractor Steve Zerby's Avatar
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    Quote Originally Posted by Homeownerinburb View Post
    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.
    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

    Quote Originally Posted by Homeownerinburb View Post
    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.
    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.

    Quote Originally Posted by Homeownerinburb View Post
    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?
    I have plenty of hand power tools that draw 13 amps alone.

    Quote Originally Posted by Homeownerinburb View Post
    BTW, you should definitely be looking into LED lighting for new construction. Seriously.
    I am. I've been swapping everything out for LEDs as I buy new bulbs now. I expect everything up her will be LED.

    Quote Originally Posted by Homeownerinburb View Post
    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.
    As I said, we are really not very far apart here.

    Thanks for your input.

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