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    AJD66's Avatar
    AJD66 Posts: 1, Reputation: 1
    New Member
    		  
    #1

    May 1, 2008, 07:26 AM
    Circuit wattage
    I am new to this website - excuse any errors. My question: I.m remodeling & wiring my basement and looking for wattgage limitations on 15 & 20 amp ckt breakers.
    AJD66
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
    Electrical & Lighting Expert
    		  
    #2

    May 1, 2008, 09:02 AM
    With regard to what? Lighting? Receptacles?
    Actually in a residence there literally is no limit. We just use common sense when figuring circuit loads.
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
    Printers & Electronics Expert
    		  
    #3

    May 1, 2008, 02:40 PM
    Mathematically speaking the limit on a 15 amp line is 1800 watts. The mathematical limit for a 20 amp line is 2400 Watts.

    The formula for calculating the minimum no. of lighting circuits is:

    3xSq. ft. (of the garage)/120 = Number of Watts (2) watts/15 or 20 (choose what lines you are working on = Min # of Circuits.

    For example: 3x1200sqft.= 3600/120 = 30 30/15 = 2
    Washington1's Avatar
    Washington1 Posts: 798, Reputation: 36
    Senior Member
    		  
    #4

    May 1, 2008, 07:06 PM
    Quote Originally Posted by stanfortyman
    With regard to what? Lighting? Receptacles?
    Actually in a residence there literally is no limit. We just use common sense when figuring circuit loads.
    I was laughing so hard when I read this, I fell on the floor:D

    It's pretty much true!

    Thanks Stan, you made my day! :)
    tkrussell's Avatar
    tkrussell Posts: 9,659, Reputation: 725
    Uber Member
    		  
    #5

    May 4, 2008, 06:50 AM
    I think the actual context of the question was missed.

    Quote Originally Posted by AJD66
    looking for wattgage limitations on 15 & 20 amp ckt breakers.
    Quote Originally Posted by stanfortyman
    With regard to what? Lighting? Receptacles?
    Actually in a residence there literally is no limit. We just use common sense when figuring circuit loads.
    Quote Originally Posted by Washington1
    I was laughing so hard when I read this, I fell on the floor

    It's pretty much true!

    Thanks Stan, you made my day!

    While there is no limitation of Quantity of outlets on a general lighting branch circuit in a residence, there is still the amperage/wattage limitations of that circuit, being 1800 watts/15 amps for a 15 amp circuit, and 2400 watts/20 amps for a 20 amp circuit.

    And since it can be reasonably assumed that any general purpose lighting circuit in a home can run fully loaded for 3 hours or more, each circuit needs to be derated down to 80 %, or 1440 watts/12 amps maximum for a 15 amp circuit, and 1920 watts/16 amps for a 20 amp circuit.

    Just thought this should be cleared up for the poster asking the question.
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
    Electrical & Lighting Expert
    		  
    #6

    May 4, 2008, 09:00 AM
    Actually no. This is taken into account with the 3 watts sq/ft.
    See NEC 220.14(J)

    Like I said, we just use common sense in figuring circuit load.
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
    Printers & Electronics Expert
    		  
    #7

    May 4, 2008, 01:35 PM
    Didn't we just come back to my original answer?
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