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Thread: Electrical question

  1. #1
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    Electrical question

    Background - my house is 55 years ols and the electrical leaves something to be desired.

    THere are no open breakers, and I wanted to add a receptacle on a wall in my basement for my transition to a workshop. After familiarizing my self with most of the breakers and remarking them I found that many of them encompass multiple floors (i.e. the main lighting in the basement is on the same breaker as the dining room?? don't ask..) ANyway I found a breaker going to a lonely receptacle in an area between the garage and finished sction of the basement. I did not have an extra receptcle so I shut the breaker off and proceeded to disconnect the "lonely" receptacle, freeing up 1 - 15 amp breaker.

    I then ran some wire to the junction box which feeds the overhead lighting and is controlled by a switch at the top of the steps. Ran the wire to a storage area underneath the steps and connected the receptacle. This being my first box electical box install I cut the hole a "smidge" to big - easy fix: I'm gonig to add a 2nd receptacle for a total of 4 outelts. 1 for a bench grinder and 1 for a Delta DP 200.

    Couple questions.

    1. Can I run electric from the 1st receptacle to the 2nd(daisy chained)?

    2. Will a 15 amp breaker be enough for 2 overhead lights flourescents, the grinder and the DP 200 considering neither the grinder nor the DP will ever be run simultaneously?

    3. Since the 15 amp breaker has been freed up and is now powering nothing can I remove the dead wire and just leave the breaker off?
    Joe

    "Is that you, Baxter? Bark twice if you're in Milwaukee. Is this Wilt Chamberlain?"

  2. #2
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    Familiarize yourself with Ohm's Law: Power = Voltage * Current

    You'll always get/know the power rating of your devices (measured in Watts or Horspower, 746 Watts = 1 Horsepower) and you'll always know your outlet voltage (usually between 110 - 120 V or 220 - 240 V) so from that, you can calculate the current you will be drawing.

    Let's assume the two fluorescents are 100 W, the grinder is 1/4 hp, and your DP is also a 1/4 hp. 100 W + 1/2 hp * 746 W/hp = 473 W. To get your current, take the power and divide by your outlet voltage: 473 W / 120 V = 3.94 A or call it 4 A. Most likely, I've rated everything higher than it will actually draw (due to guessing and inefficiencies in the motor and there will also be loss in the wire in the wall).

    So in a long-winded way, you can run all this simultaneaously on a 15 A circuit.

    Yes, you can daisy chain one receptacle to another but in a unfinished basement, I believe you need to have the circuit GFCI protected. It is a good idea to do it anyway.

    I don't see a problem leaving a breaker in your circuit panel off with nothing attached to it. I think I would remove the unused wire if it is accessible--especially if it is rather old wire that has served its purpose and is ready to be retired. If you can't remove it all, do your best to mark it as "DEAD" so that the next guy behind you knows what is going on.
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  3. #3
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    I'd suggest not running your only lighting in an area on the same breaker as a piece of machinery. Your machine trips a breaker...you're standing in the dark.

    I would also check local electrical code concerning this too.
    Ken

  4. #4
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    Not that this really matters, but that's the Basic Power Formula, sometimes (incorrectly) called Watt's Law. The watt was named in honor of James Watt, but he had nothing to do with calculating electrical power. He did coin the term Horsepower, which is often associated with power expressed as watts, so it's not completely off the mark to honor him. Ohm's Law is useful for redefining elements of the Basic Power formula to make it more useful, for instance voltage could be expressed as I * R, which would make power equal to I^2 * R

    The Basic Power Formula is actually a combination of Joule's first law (which described heat generated by current flowing through a resistor over time) and Ohm's law. Just fyi Joule's first law:

    Q = I^2 * R * t

    Which using Ohm's law could convert to:

    Q = V * I * t

    Pretty close to the Basic Power Formula...




    Quote Originally Posted by Chris Padilla View Post
    Familiarize yourself with Ohm's Law: Power = Voltage * Current

  5. #5
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    Quote Originally Posted by Jerome Hanby View Post
    Not that this really matters, but that's the Basic Power Formula, sometimes (incorrectly) called Watt's Law. The watt was named in honor of James Watt, but he had nothing to do with calculating electrical power. He did coin the term Horsepower, which is often associated with power expressed as watts, so it's not completely off the mark to honor him. Ohm's Law is useful for redefining elements of the Basic Power formula to make it more useful, for instance voltage could be expressed as I * R, which would make power equal to I^2 * R

    The Basic Power Formula is actually a combination of Joule's first law (which described heat generated by current flowing through a resistor over time) and Ohm's law. Just fyi Joule's first law:

    Q = I^2 * R * t

    Which using Ohm's law could convert to:

    Q = V * I * t

    Pretty close to the Basic Power Formula...
    Well, if you want to get rigorous about this, Joule's Law is actually:

    P = E J dv

    For a conductor with uniform cross-section, dv = dSdL so that the above equation becomes:

    P = E dL * J dS which is V * i or i*R

    P = i*R is the more commom form of Joule's Law in electric circuit theory.

    is an integral sign
    Last edited by Chris Padilla; 02-26-2008 at 2:16 PM.
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  6. #6
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    I highly recommend the Black & Decker electrical guide that you can pick up just about anywhere (Home Depot, Borders, even Wal-Mart) for less than $15. Lots of pictures and diagrams with simple, clear instructions and it covers everything I have ever needed to do, plus a lot of advanced stuff that I don't have a use for. I used mine last weekend when adding an electrical sub panel to my workshop and it was a great resource. Everything works and I didn't get shocked. What more could I ask for?

    Good luck, and remember to work safe!
    If I could ever finish working on my shop, maybe I could find the time to start working in my shop.

  7. #7
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    ??

    Quote Originally Posted by Chris Padilla View Post
    Well, if you want to get rigorous about this, Joule's Law is actually:

    P = E J dv

    For a conductor with uniform cross-section, dv = dSdL so that the above equation becomes:

    P = E dL * J dS which is V * i or i*R

    P = i*R is the more commom form of Joule's Law in electric circuit theory.

    is an integral sign.

    This seems a little involved fo my likes - give me a 12 volt dc (car audio) and I can run circles but the formulas above is a little out of my reach.
    Last edited by Chris Padilla; 02-26-2008 at 2:16 PM.
    Joe

    "Is that you, Baxter? Bark twice if you're in Milwaukee. Is this Wilt Chamberlain?"

  8. #8
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    Sorry, Joe, took off on a little calculus tangent there. Just stick with good ol Ohm's Law:

    V = i*R

    and for power:

    P = i*V = i*R = V/R
    Last edited by Chris Padilla; 02-26-2008 at 2:11 PM.
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  9. #9
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    The problem with using P=EI is that it only works in AC circuits for resistive loads.

    A 1 HP motor will produce 746 watts output, it's input power, will be greater.

    The next hurdle is that the current and voltage will not be in phase, this is called the power factor and is the cosine of the angle between the current and voltage.

    So for an AC motor, to calculate input current given power output and input voltage, you would need to know the motor power factor and efficiency.

    The easier method is to read the motor nameplate to obtain full load current.

    Motor efficiency and power factor vary widely for motors, resulting in full load currents that can vary as much as 30 to 40% for the same power rating.

    Regards, Rod.

  10. #10
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    Even if I'm off by 50% on the actual current drawn by both motors (the drill press and grinder), the 15 A circuit should suffice...agree?
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  11. #11
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    Chris, I would expect that either the grinder or the drill press could be used along with the two fluorescent fixtures on a 15 Ampere circuit.

    regards, Rod.

  12. #12
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    Quote Originally Posted by Joe D'Attilio View Post
    Background - my house is 55 years ols and the electrical leaves something to be desired ... After familiarizing my self with most of the breakers and remarking them I found that many of them encompass multiple floors.
    That doesn't surprise me. We've got some crazy wiring in our house and it was done in 1979.

    Quote Originally Posted by Joe D'Attilio View Post
    ANyway I found a breaker going to a lonely receptacle in an area between the garage and finished sction of the basement. I did not have an extra receptcle so I shut the breaker off and proceeded to disconnect the "lonely" receptacle, freeing up 1 - 15 amp breaker.

    I then ran some wire to the junction box which feeds the overhead lighting and is controlled by a switch at the top of the steps. Ran the wire to a storage area underneath the steps and connected the receptacle. This being my first box electical box install I cut the hole a "smidge" to big - easy fix: I'm gonig to add a 2nd receptacle for a total of 4 outelts. 1 for a bench grinder and 1 for a Delta DP 200.

    Couple questions.

    1. Can I run electric from the 1st receptacle to the 2nd(daisy chained)?
    Running power through a series of devices (receptacles, switches, lights, etc.) is done all the time.

    There are box fill requirements. How big is the "junction box" and what does it have going into it for cables?

    By cut the hole too big, do you mean a sloppy hole in the sheetrock so there is space around the box? If so, it's fine to replace the single-gang box with a 2-gang box and give yourself the extra receptacles. If you cut holes in the boxes for the conductors to go through, that could be a different story.


    Quote Originally Posted by Joe D'Attilio View Post
    2. Will a 15 amp breaker be enough for 2 overhead lights flourescents, the grinder and the DP 200 considering neither the grinder nor the DP will ever be run simultaneously?
    As has already been engineered to death , yep.

    I do agree with the perspective that running machinery on lighting circuits is best avoided, especially if there is a chance that you'll overload the circuit.

    Quote Originally Posted by Joe D'Attilio View Post
    3. Since the 15 amp breaker has been freed up and is now powering nothing can I remove the dead wire and just leave the breaker off?
    Yep. You could also pull the breaker and put a cover plate on the panelboard where the breaker was. Make sure you don't leave open holes in the panelboard where the cables went in.

    Rob
    Addy protocol: unlicensed, homeowner electrician

  13. #13
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    Thanks Tim

    Quote Originally Posted by Tim Thomas View Post
    I highly recommend the Black & Decker electrical guide that you can pick up just about anywhere (Home Depot, Borders, even Wal-Mart) for less than $15. Lots of pictures and diagrams with simple, clear instructions and it covers everything I have ever needed to do, plus a lot of advanced stuff that I don't have a use for. I used mine last weekend when adding an electrical sub panel to my workshop and it was a great resource. Everything works and I didn't get shocked. What more could I ask for?

    Good luck, and remember to work safe!
    Just picked 'er up - B & D Complete home wiring
    Joe

    "Is that you, Baxter? Bark twice if you're in Milwaukee. Is this Wilt Chamberlain?"

  14. #14
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    Talking Thanks everyone

    Thanks Chris even though it went over my head it's not your fault it took me 32 years to take an interst into a mechanically inclined hobby

    After a little reasearch ...NOT!!

    Actually after reading all your answers; I have figured out wha ti need to do.

    Seperate the lighting into one breaker/Dining room - don't ask

    and the open breaker I freed up I'll use for the receptacles.

    Bigger hole "than planned" problem - I kind of beat Rob to the point and just got back from the blue "borg". 4 receptacles and a sinlge pole switch for 2 new shop fluorescents.

    Picked up a well-needed shop vac a step ladder/stool, B & D COmplete guide to wiring(def an investment in the LOML's future, since I think I can do everything) and a extra gift of the COmplete guide to woodworking complete with some yokie-doke projects fit for the newbie- forgot the dust pan, broom and garbage can - had to beat the LOML home, she has been on me a bit about spending since I started this hobby but I need to get my "necessities"

    You guys are def an asset to me and the whole forum as far as that goes

    That's all for now till I run into another "Situation"
    Joe

    "Is that you, Baxter? Bark twice if you're in Milwaukee. Is this Wilt Chamberlain?"

  15. #15
    Quote Originally Posted by Joe D'Attilio View Post
    Background - my house is 55 years ols and the electrical leaves something to be desired.

    THere are no open breakers, and I wanted to add a receptacle on a wall in my basement for my transition to a workshop. After familiarizing my self with most of the breakers and remarking them I found that many of them encompass multiple floors (i.e. the main lighting in the basement is on the same breaker as the dining room?? don't ask..) ANyway I found a breaker going to a lonely receptacle in an area between the garage and finished sction of the basement. I did not have an extra receptcle so I shut the breaker off and proceeded to disconnect the "lonely" receptacle, freeing up 1 - 15 amp breaker.

    I then ran some wire to the junction box which feeds the overhead lighting and is controlled by a switch at the top of the steps. Ran the wire to a storage area underneath the steps and connected the receptacle. This being my first box electical box install I cut the hole a "smidge" to big - easy fix: I'm gonig to add a 2nd receptacle for a total of 4 outelts. 1 for a bench grinder and 1 for a Delta DP 200.

    Couple questions.

    1. Can I run electric from the 1st receptacle to the 2nd(daisy chained)?

    2. Will a 15 amp breaker be enough for 2 overhead lights flourescents, the grinder and the DP 200 considering neither the grinder nor the DP will ever be run simultaneously?

    3. Since the 15 amp breaker has been freed up and is now powering nothing can I remove the dead wire and just leave the breaker off?
    1. Yes
    2. Yes
    3. Yes

    But!!!!
    Never feed the lights from the same breaker as machinery, not a good practice.

    Flourescents need to be by theirselves. They act like a distributor when the power is turn off, arc across contacts.

    And always, when a breaker is cleared, pull the wire off. The next guy that moves in might just turn them all back on.

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