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My new range says it needs a 40-amp circuit breaker minimum. But it also says maximum draw is 13,200 watts on 120/240, so doesn't that mean a 40-amp breaker would be inadequate? By my math, max wattage on a 40-amp circuit is 9,600, de-rated to 7,680. I'm unlikely to have the oven and all five stove segments going full burn at once, but sheesh, don't I need at least 55 or 60 amps? (And 6-gauge wire?)

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According to the NEC, any household cooking appliance rated at 12kW or less can be served by a 40A circuit. Yours is over this so bumping up to a 50A would be required. The code on this can be confusing, but trust me, it's there.

I am interested in where it says a 40A circuit is acceptable.

  • I couldn't find an answer on the appliance or in the manual, so I contacted the maker. They sent me a page saying for that model, 40A or 50A. Sears, which sells it, also says that. Two things, though: 1) Do I need to upgrade to 6-gauge wire? And 2) how on earth could a 40A circuit handle 12kw? I've always heard to get amps, you divide watts by volts, and then to be safe, subtract 20 percent. Is the calculation different for cooking appliances for some reason? – Rich Jul 10 '14 at 22:16
  • Yes, that's exactly what it is. Household cooking appliances follow different codes than other circuits. And yes, you need wire capable of a 50A circuit. Depends on the wiring method you choose. – Speedy Petey Jul 11 '14 at 1:20
  • Most likely the manufacturer is saying they're okay with a 40A breaker because they're assuming you won't be using every burner + the oven + the broiler all at the same time. If you did, all that would happen is the breaker would trip. It's true that a new installation would require running a 50A circuit, but they probably spec 40A so that it can be used with grandfathered 40A circuits without rewiring. – Nate Strickland Apr 9 at 16:07
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Ranges are special

Range/cooker loads in the NEC are governed by the demand factors in Table 220.55; this is stated outright in NEC 422.10(A) paragraph 4:

Branch circuits and branch-circuit conductors for household ranges and cooking appliances shall be permitted to be in accordance with Table 220.55 and shall be sized in accordance with 210.19(A)(3).

as well as Table 220.55, note 4:

  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.

...and it turns out the OP is OK

As a result of this, we take the baseline 8kW from Column C of table 220.55 for a single 12kW range, and then apply the Note 1 adjustment as the range in question is a 13.2kW unit:

  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 this, we get a 15% upward adjustment on the Column C value, or 8kW * 1.15 = 9.2kW, which is less than the 9.6kW a 40A circuit can handle, so the OP is good to go. We use 9.6kW here because the table 220.55 sizing overrides the normal continuous-load provisions in the NEC, by the way.

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our stove/oven has 40 amp breaker & rated for 12.5 KW . its done fine for years with no breaker issues. yes, if you add or need/required to use a 50 amp you will need to use at least 6 gauge wire. if you didn't the 8 gauge wire could get hot & the 50 amp breaker may not trip or click off because it is rated higher. always match the wire to the breaker.

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