romex wire and breaker to use

Discussion in 'Electrical Forum discussion & Blog' started by solutions, Mar 30, 2008.

  1. solutions

    solutions New Member

    Messages:
    22
    I would like to install a motion light. It is 750 watts total (each of the three lights 250 watts) In the place i want to install the fixture, has existing 14/2 that goes to a 15 amp breaker. At the big box store they tell me 14/2 will work ok with a 15 amp breaker( very leary of there advice in general) but is 14/2 the safest and best to run this type lighting and wattage?

    Thank you all!!
  2. jimbo

    jimbo Plumber

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    8,997
    Location:
    San Diego
    750 watts is about 6 amps. The general rule in residential wiring is that a 15 amp breaker can be wired to 14 guage wire, and should have a continuous load not exceeding 12 amps. ( Short term uses like a toaster, or hair dryers, are not condsidered contiuous. A light fixture is.)
    If there are no other loads on the circuit ,you are fine. If there are other loads, then you would have to evaluate the whole picture.
  3. solutions

    solutions New Member

    Messages:
    22
    Thanks for the reply Jimbo..Sounds great! Yep, the motion sensor light will be the only thing on the circuit.
  4. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Location:
    North Carolina

    Jimbo-
    There is no such thing as a continuous load in residential wiring even if it is left on 24 hours a day 7 days a week.
  5. jimbo

    jimbo Plumber

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    8,997
    Location:
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    Well, what do you expect on a plumber's forum!!! But what is this 80% rule we hear about? How many ampls can you put on a 15 amp circuit?
  6. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    999
    Location:
    NY State, USA
    If you consider this a "Plumber's forum", then why bother having topics like "Electrical Forum discussions"?
  7. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    999
    Location:
    NY State, USA
    This is one of the few times I have to disagree with Mike.

    Things like some lighting and electric heaters are considered continuous loads, by direct statements or by definition.
  8. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Location:
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    It’s perfectly okay to disagree with me and sometimes I learn from the debate.

    When you say that electric heaters are considered continuous loads by direct statement you would be correct as outlined in section 424.3(B) Branch-Circuit Sizing. Fixed electric space heating equipment shall be considered continuous load and even 422.13 for water heaters.

    But for lighting the load is simply three watts pre square foot and it is not considered a continuous load in residential applications. In other words an 1800 watt lighting load on a 15 amp circuit in a residential circuit is 1800 watts for three minutes or for three days.
    There is no requirement of do the three hours or more is continuous for residential lighting circuits. For the general purpose and small appliance circuits there is no minimum or maximum number that is allowed. The only limit is outlined in 220.14(J).

    It would be a good design to limit the number of lighting outlets on one circuit but it is not a code requirement.
  9. Chris75

    Chris75 Electrician

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    608
    Location:
    Litchfield, CT
    I agree with JW, Continuous loads in residential are far and few...
  10. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    999
    Location:
    NY State, USA
    To be honest I never thought of it that way, meaning that it is included in the demand load like that, even for additional circuits.

    I get what you mean now.
  11. jimbo

    jimbo Plumber

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    8,997
    Location:
    San Diego

    I generally consider there to be two categories of questions here....DIY questions which can be answered by plumbers with DIY-type general knowledge, and more technical questions. I stay away from the second type for sure, but sometimes try to help on the first category.


    Anyway, just for my own knowledge....could you install an 1800 watt baseboard heater on a 15 amp circuit, with 12 guage? May or may not be a good idea....but would it comply with code?
  12. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    999
    Location:
    NY State, USA
    No. Electric heat is considered a continuous load.

    210.20 Overcurrent Protection
    Branch-circuit conductors and equipment shall be protected by overcurrent protective devices that have a rating or setting that complies with 210.20(A) through (D).

    (A) Continuous and Noncontinuous Loads Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the rating of the overcurrent device shall not be less than the noncontinuous load plus 125 percent of the continuous load.


    But the question begs: If using #12 WHY bother with a 15A breaker in the first place?
  13. mikept

    mikept DIY Senior Member

    Messages:
    152
    Location:
    CT
    Old #12Al...
  14. kd

    kd New Member

    Messages:
    207
    When talking about wire, we assume it is Copper. If you are using Aluminum please tell us.
  15. jimbo

    jimbo Plumber

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    8,997
    Location:
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    Well, that was the point of my question, because JW had posted this :
    "Jimbo-
    There is no such thing as a continuous load in residential wiring even if it is left on 24 hours a day 7 days a week."

    Now, I'm confused!
    [​IMG]
  16. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    999
    Location:
    NY State, USA
    Re-read post #8.
  17. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
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    Location:
    North Carolina
    Don't be confused as I may have spoke a little premature in my first post. When doing the branch circuit supplying any resistive load then the 125% rule comes into play but when doing a service calculation the 125% does not come into play on residetial loads.
  18. jimbo

    jimbo Plumber

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    8,997
    Location:
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    Thanks very much. I'm going back to clogged toilets!!
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