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  • House - Standard Load Calculation - Need Help

    I'm an apprentice, my license electrician Journeymen handed me the Standard Load Calculation form for a job I'm working on. It's an existing home, with a 150 Amp Service. He wants to see if I can sink or swim. I have no training or education on the load calculation, I spent the past 8 hours with the 2008 NEC (will get 2011 with classes in spring)... this is where I'm at. Any help would be greatly appreciated.

    Any links to "example" standard load calculations would be great.

    1. General Lighting : Table 220.12

    3450 square feet X 3 VA = 10,350 VA
    1500VA (small appliance) x 2 = 3,000 VA
    1500VA (laundry) x 1 = 1,500 VA

    Total 14,850 VA

    First 3,000 VA @ 100% = 3,000 VA
    Next 11,850 VA @ 35% = 4,148 VA

    Total 7,148 VA
    Total Phase__________? VA
    Total Neutral ________? VA

    --------------------------------------------------------

    2. Fixed Appliances: 250.53

    Dishwasher = 168 VA ---> 1.4 amps
    Disposal = 972 VA ----> 8.1 amps
    Total = 1140 VA

    1140 VA x 75% = 855 VA

    _______? VA Phase
    _______? VA Neutral (120 V loads at 75%)

    --------------------------------------------------------

    3. Dryer:220.53; 220.53

    It's a mini size dryer, rated at 12 amps or 2880 VA. But codes says "5000 VA or name plate rating, which ever is larger".

    5,000 VA x 100% = 5,000 VA

    _______? VA Phases
    _______? VA Neutral x 70%

    ------------------------------------------------------------

    4. Cooking Equipment: Table 22.55; Notes

    I'm totally lost here... with col. A, B, C

    Cooktop 7 Kv = 7,000 VA
    Oven 3.7 Kv = 3,700 VA

    Col A _______ VA x _______% = _______ VA
    Col B _______ VA x _______% = _______ VA
    Col C _______ VA x _______% = _______ VA

    _______? VA Phase
    _______? VA Neutral x 70%

    -----------------------------------------------------------

    5. Heating or A/C: 220.60

    A/C = 5,280 VA x 100% = 5,280 VA

    ______? VA Phase
    ______? VA Neutral

    -----------------------------------------------------------

    6. Largest Motor

    I don't understand this... I did my A/C above.

    ------------------------------------------------------------

    Phases I = ___ VA / ___ V = ___ A
    Neutral I = ___ VA / ___ V = ___ A

    ____ VA Phases
    ____ VA Neutral

    220.61(B) First 200 A x 100% = 200 A
    Remaining ____ A x 70% =

  • #2
    Re: House - Standard Load Calculation - Need Help

    that's like having your parents do your homework

    don't forget to ground your work to our cold water main and also the gas to cold.

    rick.
    phoebe it is

    Comment


    • #3
      Re: House - Standard Load Calculation - Need Help

      All discussion forums are "parents do my homework". I really need a good example to reference off.

      My Journeyman isn't gonna expect me to get this 100% correct. He wants to see me put forth the effort. I'm just not willing to quit yet, any push in the right direction would help.

      Comment


      • #4
        Re: House - Standard Load Calculation - Need Help

        Originally posted by PLUMBER RICK View Post

        don't forget to ground your work to our cold water main and also the gas to cold.

        rick.
        That's a joke, right?

        I have never have grounded gas lines to water lines. When I install a new service we install 2 ground rods 6' apart with a single ground wire to the meter. Then run a ground line from the meter to the water pressure valve, clamp it down before/after the pressure valve. Last we just bond the cold/hot water lines at the water heater.

        Comment


        • #5
          Re: House - Standard Load Calculation - Need Help

          not sure about georgia, but out here, the gas pipe is also grounded to the water piping. so no, not a joke

          rick.
          phoebe it is

          Comment


          • #6
            Re: House - Standard Load Calculation - Need Help

            I think the correct term is to "bond" the water and gas lines not ground them,
            (basically it is the same difference to a non electrician as there all connected by a wire, to the ground/earth of the buildings wiring system, but to a electrician there two different things). (and the definition has been changing some over the last few years, for better clarity)

            Grounded [100]. Connected to earth.


            Bonding [100]. The permanent joining of metal parts together to form an electrically conductive path that has the capacity to conduct safely any fault current likely to be imposed on it.
            http://ecmweb.com/nec/code_top50nec_082806/


            1.When you ground, you connect something to the earth. Think of this as earthing.

            2.When you bond, you create a conductive path between metallic objects.

            3.Bonding is the method by which you create a low-impedance path for fault current to flow.
            http://ecmweb.com/grounding/electric...vs_bonding_11/
            for a more in depth look http://ecmweb.com/topics/grounding-vs-bonding/



            It is my understanding all "metallic systems" in a home/building that are capable of being energized are required to be bonded to the grounding system. This is usually taken to mean: metallic water supply, metallic drain-waste-vent pipe, metal ducting, gas lines, and many times metallic structural elements.

            Although you don't need to ground piping systems and structural steel, you do need to bond them. And you need to bond them in a manner that establishes an effective ground-fault current path [250.4(A)(4)].
            http://ecmweb.com/grounding/electric...vs_bonding_10/
            here is the section of the article on bonding water/gas pipes and metal in a structure, http://ecmweb.com/grounding/electric...vs_bonding_10/

            the article is based on the 2005 electrical code but is still totally applicable,

            as far as the load calculations I am sorry can't really help you out there, but there is a lot of info on the net, do a Google search on "electrical load calculations"
            Last edited by BHD; 03-10-2011, 06:17 PM.
            Push sticks/blocks Save Fingers
            ~~~~~~~~~~~~~~~~~~~
            "The true measure of a man is how he treats someone who can do him absolutely no good."
            attributed to Samuel Johnson
            ~~~~~~~~~~~~~~~~~~~
            PUBLIC NOTICE: Due to recent budget cuts, the rising cost of electricity, gas, and oil...plus the current state of the economy............the light at the end of the tunnel, has been turned off.

            Comment


            • #7
              Re: House - Standard Load Calculation - Need Help

              I believe I have it right now...

              1. General Lighting : Table 220.12

              3450 square feet X 3 VA = 10,350 VA
              1500VA (small appliance) x 2 = 3,000 VA
              1500VA (laundry) x 1 = 1,500 VA
              -----
              Sum Total 14,850 VA


              First 3,000 VA @ 100% = 3,000 VA
              Next 11,850 VA @ 35% = 4,148 VA
              ------
              Sum Total = 7,148 VA

              Total Phase = 7,148 VA
              Total Neutral = 7,148 VA

              --------------------------------------------------------

              2. Fixed Appliances: 250.53

              Dishwasher = 168 VA
              Disposal = 972 VA
              Cloth Washer = 1440 VA
              ------
              Sum Total = 2580 VA


              2580 VA x 75% = 1935 VA


              1935 VA Phase
              1451 VA Neutral @ 75% (1935 VA x 75% = 1451 VA)

              --------------------------------------------------------

              3. Dryer:220.53; 220.53

              5,000 VA x 100% = 5,000 VA

              5,000 VA Phases
              3,500 VA Neutral @ 70% (5,000 VA x 70% = 3,500 VA)

              ------------------------------------------------------------

              4. Cooking Equipment: Table 22.55; Notes

              10,700 VA x 65% = 6955 VA

              6955 VA Phase
              4869 VA Neutral @ 70% (6955 VA x 70% = 4869 VA)

              -----------------------------------------------------------

              5. Heating or A/C: 220.60

              5,280 VA x 100% = 5,280 VA

              5,280 VA Phase
              5,280 VA Neutral

              -----------------------------------------------------------

              6. Largest Motor

              (/) 5,280 VA x 25% = 1,320 VA
              N 5,280 VA x 25% = 1,320 VA

              1,320 VA Phase
              1,320 VA Neutral


              ------------------------------------------------------------

              Sum Phases = 27,638 VA

              Phases I = ___ VA / ___ V = ___ A

              27,638 VA / 240 Volts = 115 Amps

              -------

              Sum Neutral = 23,568 VA

              Neutral I = ___ VA / ___ V = ___ A

              23,568 VA / 240 Volts = 98 Amps

              Phases = 115 Amps
              Neutral = 98 Amps

              I should not be overloading a 150 amp service, assuming 120 amps is the safety mark.

              Comment


              • #8
                Re: House - Standard Load Calculation - Need Help

                Originally posted by Joey View Post
                I believe I have it right now...

                1. General Lighting : Table 220.12

                3450 square feet X 3 VA = 10,350 VA
                1500VA (small appliance) x 2 = 3,000 VA
                1500VA (laundry) x 1 = 1,500 VA
                -----
                Sum Total 14,850 VA


                First 3,000 VA @ 100% = 3,000 VA
                Next 11,850 VA @ 35% = 4,148 VA
                ------
                Sum Total = 7,148 VA

                Total Phase = 7,148 VA
                Total Neutral = 7,148 VA

                --------------------------------------------------------

                2. Fixed Appliances: 250.53

                Dishwasher = 168 VA
                Disposal = 972 VA
                Cloth Washer = 1440 VA
                ------
                Sum Total = 2580 VA


                2580 VA x 75% = 1935 VA


                1935 VA Phase
                1451 VA Neutral @ 75% (1935 VA x 75% = 1451 VA)

                --------------------------------------------------------

                3. Dryer:220.53; 220.53

                5,000 VA x 100% = 5,000 VA

                5,000 VA Phases
                3,500 VA Neutral @ 70% (5,000 VA x 70% = 3,500 VA)

                ------------------------------------------------------------

                4. Cooking Equipment: Table 22.55; Notes

                10,700 VA x 65% = 6955 VA

                6955 VA Phase
                4869 VA Neutral @ 70% (6955 VA x 70% = 4869 VA)

                -----------------------------------------------------------

                5. Heating or A/C: 220.60

                5,280 VA x 100% = 5,280 VA

                5,280 VA Phase
                5,280 VA Neutral

                -----------------------------------------------------------

                6. Largest Motor

                (/) 5,280 VA x 25% = 1,320 VA
                N 5,280 VA x 25% = 1,320 VA

                1,320 VA Phase
                1,320 VA Neutral


                ------------------------------------------------------------

                Sum Phases = 27,638 VA

                Phases I = ___ VA / ___ V = ___ A

                27,638 VA / 240 Volts = 115 Amps

                -------

                Sum Neutral = 23,568 VA

                Neutral I = ___ VA / ___ V = ___ A

                23,568 VA / 240 Volts = 98 Amps

                Phases = 115 Amps
                Neutral = 98 Amps

                I should not be overloading a 150 amp service, assuming 120 amps is the safety mark.
                Sorry for the late post, but I just joined today. You can only derate the applainces if there are four or more fastened in place. Otherwise it's 100%.

                Comment


                • #9
                  Re: House - Standard Load Calculation - Need Help

                  Welcome to the board "Electures". hope you enjoy,
                  Push sticks/blocks Save Fingers
                  ~~~~~~~~~~~~~~~~~~~
                  "The true measure of a man is how he treats someone who can do him absolutely no good."
                  attributed to Samuel Johnson
                  ~~~~~~~~~~~~~~~~~~~
                  PUBLIC NOTICE: Due to recent budget cuts, the rising cost of electricity, gas, and oil...plus the current state of the economy............the light at the end of the tunnel, has been turned off.

                  Comment


                  • #10
                    Re: House - Standard Load Calculation - Need Help

                    Originally posted by BHD View Post
                    Welcome to the board "Electures". hope you enjoy,
                    What he said.

                    Comment

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