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enter image description hereThe cook top I am replacing (a small, old Credo unit) uses a 2P 30A Circuit breaker.

The similarly small new Summit cooktop I plan to install has the following electrical specs:

  • Connection voltage: 220-240 VAC 60Hz 29A
  • Max connected power load: 6400W.
  • "Electrical requirements" specify that "the socket should comply with relevent electrical standards, or should contain a 1P circuit breaker with electrical loading of at least 40A."

What I'm thinking is that I'll have to replace the 30A 2P breaker with a 40A 1P breaker and change out the wiring from 10g (which I presume it is, but will check first) to 8g.

But, what I HOPE, is that the connection voltage and 6400W power load indicated for the Summit (@ 29A) means I could install it without changing out the wiring or the circuit breakers. Would that work?

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  • 1
    You do need a 2 pole breaker if you're in the US -- all 240V power here uses both poles. In European-style 240V, you could do it with a single pole -- that's why they say you also need to comply with local electrical codes.
    – Nate S.
    Commented Jul 14, 2020 at 23:21
  • And if you do end up replacing the wiring, I'd recommend you go ahead and put in wiring good for 50A. It won't cost much more, but that way if you (or a future owner) will be able to plug in any stove without changing the wiring again.
    – Nate S.
    Commented Jul 14, 2020 at 23:23
  • I think you misread the 1 pole or you are on a different continent not North America. I say this as every thing is correct except the 1 pole breaker did they mean 1 handle or common trip ? While I was typing this Nate jumped in also + we just need to verify as you used #8 & #10 wire sizes not common for the other side of the pond and you have a double pole 30.
    – Ed Beal
    Commented Jul 14, 2020 at 23:26
  • These comments help a lot. I'm in the states and bought the stovetop here, but I think it's probably a popular sale item for Summit (a US company) in Europe, since it's quite small: 24"by 20". I am assuming "a 1P circuit breaker with electrical loading of at least 40A" means a 40A single pole breaker, but I could not find one on sale and you guys helped me understand why. As for the existing wiring it is 10g, with the double pole 30A breaker - a black wire and a red wire plus a white ground wire. If I were to change the wiring, what gauge goes with a 50A breaker...6? Thanks again!
    – Cliff
    Commented Jul 15, 2020 at 15:48
  • @Cliff, yes, #6 would be appropriate for 50A if you're changing the wire. But if I were you I'd probably go with ThreePhase's answer and keep using the wiring you have, and only upgrade it if you get a bigger stove in the future.
    – Nate S.
    Commented Jul 15, 2020 at 17:07

1 Answer 1

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You can keep the existing wiring and breaker

Range loads are computed from their wattage, based on the rules in NEC's Table 220.55. In particular, since 422.10(A) paragraph 4 explicitly permits range loads to be sized as per Table 220.55:

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).

we can then apply the logic from Note 4 to Table 220.55 to our situation:

  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.

In our case, given that we have a 6.4kW, 240V cooktop, we treat this as the branch-circuit size, without derating, giving us something in the 27A range. As a result, since we're below the 8.75kW threshold set by NEC 210.19(A)(3), we can use that as our branch circuit load, giving us a 30A branch circuit and breaker with 10AWG wire. Since it's a 220-240V appliance and not a 110/220 or 120/240V one, we also know that it has no use for a neutral, which means that's not a concern when wiring this, either. In your case, since you are dealing with a conduit run for the existing branch circuit, the new cooktop needs to be wired the same way the old one was: black to black, red to red, and green to the box, with the white wire in the box left capped off as it is right now.

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  • I remembered the derate for multiples, but forgot ranges have the exception, +
    – Ed Beal
    Commented Jul 15, 2020 at 13:13
  • Well, thats great news, ThreePhase! I did the simple math and got 27A, too. There's currently red, black and a white ground wire. According the installation guide, I will connect the unit's black and red wires to one (black, let's say) and its yellow and white wires to the other (red) and the green to the white one. (The current stove top [a similarly small Creda unit] ground wire was screwed into the metal junction box.) Thank you for your guidance!
    – Cliff
    Commented Jul 15, 2020 at 15:47
  • @Cliff -- can you post a photo of the inside of the junction box? It sounds like your white's a neutral, not a ground, and shouldn't be treated as a grounding means Commented Jul 15, 2020 at 15:51
  • Yes, but it may take a minute! Don't see how you upload photos.
    – Cliff
    Commented Jul 15, 2020 at 16:27
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    Yes. Here is the address to the product, with four different links to specs and installation instructions: summitappliance.com/catalog/model/CR4B23T5B
    – Cliff
    Commented Jul 16, 2020 at 19:21

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