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Existing 40amp breaker and #8 wire to old range I have removed. I added a box at the removed 240 receptacle. Can I add my new stovetop at 9.6Kw and wall oven at 6.4Kw to this added box?

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Your proposed combination exactly fits onto this branch circuit

Since we are putting a cooktop and a wall oven on the same circuit, the provisions in Note 4 to Table 220.55 direct us to treat the sum total of their loads as the equivalent of a single range:

  1. Branch-Circuit Load. It shall be permissible to calculate the branch-circuit load for one range in accordance with Table 220.55. The branch-circuit load for one wall-mounted oven or one counter-mounted cooking unit shall be the nameplate rating of the appliance. The branch-circuit load for a counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same room, shall be calculated by adding the nameplate rating of the individual appliances and treating this total as equivalent to one range.

For your cooktop and oven, this gives us 9.6kW + 6.4kW = 16kW of equivalent range load. We then apply Note 1 to this equivalent range load:

  1. Over 12 kW through 27 kW ranges all of same rating. For ranges individually rated more than 12 kW but not more than 27 kW, the maximum demand in Column C shall be increased 5 percent for each additional kilowatt of rating or major fraction thereof by which the rating of individual ranges exceeds 12 kW.

From that 16kW load, we can derive that it's 4kW over the 12kW upper limit on Column C of the table, so we need to up the 8kW Column C figure by 20% (4 * 5%), which gives us 8kW times 1.2, or 9.6kW as our final answer. This is precisely what a 40A, 240V circuit can handle, so you're good to go.

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  • However there is a Note: Assuming you newer have all at sam time the ranges will never be on at the same time and with thermostats on ovens and range eyes the load will be much less than the sum of the nameplates. Makes sense, but what if you do, then the total consumption would be the rated consumption, till the thermostats turn off. IE, 9.6 kW would be 9.6 kW till the thermostat activates. Why else is the rating spec ?
    – Traveler
    Commented Jun 22, 2022 at 1:21
  • @knowitall -- you see individual elements cycling on and off with a range, cooktop, or even an oven, and over a short enough timespan that what matters (heat in the wires) is much less than a load that pulls 9.6kW continuously for that span of times Commented Jun 22, 2022 at 1:34
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    @knowitall Code also takes into account that in reality there is some allowance in the thermal rating of wires. A wire doesn't suddenly catch on fire at 41A. So yes, there will be some time (perhaps minutes at a time, even) where it happens that all burners are cycled on and the oven bake and broil elements are both on and total power may be a good bit over the rated wire capacity/breaker. But that is short term - if it is truly long term the breaker will trip. The same could be said relative to load calculations for a panel - in a typical house if you plugged in and turned on a hair dryer Commented Jun 22, 2022 at 3:31
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    And Thanksgiving full load isn't what you might think it is. Put the turkey in the oven and after initial heating the bake element might run 20% of the time and the broil element not all. Start the big pot of soup on high, but once it reaches a boil you turn it down to simmer on low for an hour. Commented Jun 22, 2022 at 3:34
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    The code (load calculations for a panel) is also based on assumptions about power use elsewhere. If you have 100A service and plug a 16A bitcoin miner into every 20A circuit in your house (let's say 2 in kitchen, 1 in each of 2 bathrooms, 2 in general circuits = 7 x 16 = 112A), you can't rely on the standard load calculation either! If you are a semi-pro cook or are running a bakery out of your kitchen, you have to adjust things accordingly. But code handles typical usage extremely well. Commented Jun 22, 2022 at 3:44

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