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

  1. #16
    DIY Senior Member Homeownerinburb's Avatar
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    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.

  2. #17
    DIY Senior Member bluebinky's Avatar
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    Use 12 ga if you insist. It is not as safe as 15 amp circuits.
    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...

  3. #18
    DIY Senior Member Homeownerinburb's Avatar
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    Quote Originally Posted by bluebinky View Post
    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...
    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.

  4. #19
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by bluebinky View Post
    Where's the data that shows a properly installed 15A circuit is safer?
    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?

  5. #20
    Remodel Contractor Steve Zerby's Avatar
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    Well I'm definitely learning things here. This is a marvelous forum. I am taking all of the information to heart.

    Quote Originally Posted by Homeownerinburb View Post
    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.
    Sorry if I developed some attitude, but this passage just set me off a little:

    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.
    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 by Steve Zerby; 06-18-2013 at 06:41 AM.

  6. #21
    DIY Senior Member bluebinky's Avatar
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    Thanks JW.

    And yes, LED lighting is for real IMHO. I like the new Cree bulbs sold in some HD stores. My entire bedroom now uses less than 25 W with everything on max. By insulating, putting in a new furnace and windows, LED lighting, etc, I've cut my power and gas usage by about half -- and have a more comfortable environment.

    When it comes to a workshop, more is better -- to a point. The average usage is actually quite low, but the peak can be high...

  7. #22
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Steve Zerby View Post
    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.
    I have been doing electrical contracting work for over 44 years and have yet to see a saw service installed for the construction of a home that would carry every electrical tool on the market today.

    It is not a case of installing a circuit big enough to handle all these tools at one time but it is instead a matter of managing the tools being used at one time.

    Any dust collector of any size to control lead dust should always be on its own circuit with no other tool. Should your air compressor be of any size at all it also should be on a circuit of its own and not shared with any other motor load.

    A half horse power 120 volt motor for a tool when just running and not cutting will draw ~ 10 amps but lock the motor and it will draw ~ 59 amps. In order to start the motor to turning without any load at all it will for a nanosecond draw 59 amps.

    Knowing this and then trying to saw while a dust collector and air compressor is plugged into the same circuit is doing nothing but burning out the motors.

    It is not a matter of bigger circuits but a tool management problem. Do the math to see for one self just what motor tools do. Multiply the full load amps by 6 to see what the maximum amp draw of the motor will be. A 1/3 hp motor draws 7.2 FLA (full load amps) a hp draws 9.8, a hp draws 13.8 and a 1 hp draws 16 amps. You will find they draw a LRA (locked rotor amps) of 43.2, 58.8, 82.8, and 96 amps respectfully. To check my numbers one can reference Tables 430.248 FLA for 120 volt motors and 430.251(A) LRC of the NEC.

    Installing a larger circuit just so we can operate two or more of these appliances at one time just means that there is more heat energy available when we have other problems.

    Edited to add:

    It has also been my experience that shop tools just don’t do very well plugged into a 15 amp circuit. It is illegal to use the general purpose circuit of a home for renovations purposes unless the tool being used if protected by a GFCI device.

    I don’t know of the times that I have been called by a remodeler to look at the circuits in someone’s home because the breaker kept tripping during construction. A smart contractor will have a temp service installed for any remodel work instead of trying to use the premises wiring of the home they are working on but alas it continues to be done none the less.

    Should you try to use the premises wiring for your tools then learn how to manage the tools being used at one time and the problem will diminish
    Last edited by jwelectric; 06-18-2013 at 11:26 AM. Reason: fix quote

  8. #23
    DIY Senior Member Homeownerinburb's Avatar
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    JW, thanks for stepping in there and explaining the drawbacks of 20 amp circuits as general lighting circuits. I just don't explain it the way you do.

    Steve, sorry if I sounded snotty, but I did say I was confused, and then you acknowledged that you were joking. I have seen several 1000 sqft bungalows from the '40s have a second story put on them, a standard sized lot around here is 6000sqft and often it makes more sense to go up. But I know that the floor must be torn out and all the foundations reinforced. So if you want to joke about going to a third floor, you will trip me up.

    Back to your concerns about load demand. Yes, once upon a time 60 amp services with four fuses were common in the bungalows around here. I have replaced a few of them, but there are not many that were not updated decades ago. And those updates are getting replaced.

    But efficiency is king. You were positing the demand of dozens of halogen lights. And now you acknowledge that LEDs are available and obviously are more efficient.

    The CURRENT code demands that you provide 3 va per sq ft, which works out to 42.5 amps, in general lighting circuits. You don't get to round down.

    So you can install three 20 amp circuits and deliver 60 amps, or three 15 amp circuits and deliver 45 amps, or take my advice, and put in four 15 amp circuits and have 60 amps available, which is about 30% over the minimum requirement. Quicker, cheaper, easier, and as JW illustrated, SAFER.

    And shop around for some more efficient TVs please, the ice caps are melting. While you are wiring the room, you can put a switch on the wall that turns off all the power to the entertainment "vampire" load. That stuff is deadly on your electric bill. There is no need to have it on when it is not in use, is there?

    You mentioned the idea of a new kitchen addition. When I work up such a project, I assume six circuits or so. Two 20 amp counter circuits. A 20 amp dedicated circuit over the stove for the inevitable microwave range hood (my inspectors really push that one, and I don't currently push back). The garbage disposal and dishwasher get another dedicated 20 amp circuit, and both of them have cords that plug into an outlet, that is the latest code.

    The refrigerator I always put on a dedicated circuit when working from scratch, why not? 15 amp is sufficient unless it is big enough to hang sides of beef in.

    If the laundry is anywhere near by, it gets a dedicated 20 amp circuit. And the lighting for the kitchen is on none of the circuits described.

    On one occasion it made sense for me to just put in a 50 amp subpanel for the whole kitchen, that ended up saving lots of wire. Most of the time, the original plan has the service panel near the kitchen for obvious reasons, so that was the exception. What you describe may be another exception.

  9. #24
    DIY Senior Member Homeownerinburb's Avatar
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    Sorry, duplicate
    Last edited by Homeownerinburb; 06-18-2013 at 01:43 PM.

  10. #25
    DIY Senior Member Homeownerinburb's Avatar
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    Quote Originally Posted by bluebinky View Post
    Thanks JW.

    When it comes to a workshop, more is better -- to a point. The average usage is actually quite low, but the peak can be high...
    Obviously, a workshop is a horse of another color compared to the general lighting circuits in the house.

    My experience has been that a 30 amp service feeding four 20 amp circuits gets the job done for most of my clients.

    Many guys are pretty optimistic about how much time they are going to be out there and how many tools they are going to run.

    JW is quite right: a dedicated circuit for the dust collector, another for the air compressor, another for the various power tools that one is only going to be working one at a time anyway, another for the AC, and find some way to get lighting in there.

    The AC can be 240v, which helps balance the load down the service feed.

    Or make it 40 or 50 amp. I'll deposit the check all the same.

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