Replacing an Electric Cooktop on a 20A Circuit, Advice?

crungle on 13/01/2021 - 15:00

Hi all,

So our crappy 90s Chef brand 60cm coil cooktop has given up the ghost. Looking to replace it relatively on the cheap, ideally just grabbing another cooktop that fits and paying someone to come and swap it out. We're not particularly fussed about induction — happy to just pop a good value electric ceramic in.

However, this is all admittedly new to me, and I'm struggling to figure out how to find something that will definitely work on the existing 20A circuit. (Side note: on the circuitboard, the cooktop and stove each have their own 20A circuit breakers. Does this mean they definitely have their own circuits?)

I gather that a 4.8kW max draw capacity is advised for 20A — although up to 8kW is standards compliant, presumably meaning it'll flip the breaker before burning the house down. However, it seems impossible to find any 60cm cooktops that low in Aus these days — even all the cheap ceramics I've checked out are 5.8-7.4kW+. The closest I can find are induction hobs that allow you to customise their maximum draw. I'm tempted, but would like to figure out cheaper solutions first.

Now surely all the thousands of cheapo reno jobs out there aren't paying for new 32A circuits just to whack in their $200 Aldi ceramic cooktops — so what's the deal? Am I just not looking in the right places?

Any links to decent electric cooktops that'll be fine on a 20A circuit, and general info/advice, would be great.

TIA!

Electrical & Electronics

Comments

  • kongkurr on 13/01/2021 - 15:31
    +4

    A 20A supply will generally easily allow for two large burners to be used together, or one large and one small. Depending on cooktop, a third will probably also run without tripping the circuit breaker (several variables here).

    Your sparky will be able to reference Table C5 of AS3000, which recommends a 20A circuit for a cooking appliance rated between 5000 & 8000W. As long as you don't expect to be using all burners at the same time, this is a safe and certified method of installation.

    For reference, the last 60cm I measured ran 11.5A with two burners on.
    I can't imagine any domestic 60cm not being suitable for you, however be aware of any manufactures instructions that may void warranty if x cable size or circuit protection isn't installed.

    Two separate breakers in your switchboard should indicate individual circuits being run to each appliance, just ensure that those two breakers aren't connected together (a two module wide breaker with switch connected), which would indicate a 2 phase circuit, but that would be rare.

    • crungle on 13/01/2021 - 15:55

      Hey mate, thanks so much for the thorough and extremely insightful response. Definitely don't expect to be using all the burners at once.

      A couple questions: say I do get a cooktop with a maximum draw exceeding 20A but within that 5000-8000 range, and someone does somehow end up attempting to draw >20A. Is that specifically unsafe? Won't it just trip the breaker and be an "oh, right, too much juice, oops" moment?

      Second, if I buy cooktop within that 5000-8000 range, which might specifically recommend a 25A or 32A in its manual, and ask a sparky to install it, will that definitely be a go or is this contentious among sparkies. Any chance he'll get out here and call me an idiot and insist on only installing if I put the recommended circuit in?

      And finally, would you be willing to take a look at my circuitboard to confirm if my assessment of the situation is definitely accurate? Here it is

      Once again, really appreciate the help!

      • kongkurr on 13/01/2021 - 16:28
        +2

        I use 'unsafe' in more of a legal standpoint, and for liability purposes - being circuit breakers and not fuses, there is minimal risk involved.

        It would only be contentious to someone without a great enough understanding, who wouldn't install them regularly (a regular domestic sparky won't question it, but your industrial sparky cousin may). If questioned, quote the clause I mentioned.

        Your switchboard is fine, you're correct in saying you have separate circuits for both oven and cooktop.

        My first comment on how many burners to trip the breaker was incorrect in hindsight. As someone said below, you'll be unlikely to trip even with 4 burners running due to the way a circuit breaker trips over time, and if burners are toggling on and off with thermostats.

        • crungle on 13/01/2021 - 17:01

          Awesome. That's pretty much all the confusion and ambiguity resolved for me. I feel a lot more confident going ahead now. Stoked! Thanks a ton.

  • abb on 13/01/2021 - 15:43

    on the circuitboard, the cooktop and stove each have their own 20A circuit breakers. Does this mean they definitely have their own circuits?

    How does the stove differ from the cooktop??

    One of those 20A circuits is probably the Oven, right?

    • crungle on 13/01/2021 - 15:44

      Oops, slip of the tongue. By stove I meant oven. Here's the circuitboard if you're curious

      • abb on 13/01/2021 - 15:48

        All good, yep those will be one circuit per breaker.

        FYI: 4.8kW is the maximum sustained power draw that the breaker will allow. But the 8kW rating you'll see in the cooktop catalogue is the peak power level - all 'burners' going flat out.

        Your breaker will trip if you run all 4 burners at full for some time, but will not trip under normal cooking scenarios :)

        • crungle on 13/01/2021 - 16:01

          Sweet, yeah, that's basically what I figured, but it's been surprisingly hard to confirm or deny that through Google-fu alone. Thanks :)

      • Muzeeb on 13/01/2021 - 15:54

        Here's the circuitboard if you're curious

        The way the permanent marker lines don't line up with the breakers is mildly infuriating

        • crungle on 13/01/2021 - 15:57
          +1

          Haha, I feel the same. Had it been me I would've wiped it off and done it again for the sake of my spiritual wellbeing

  • jv on 13/01/2021 - 16:04

    Advice?

    Get a gas one.

  • Connected on 14/01/2021 - 12:01
    +2

    With some induction cooktops you can set the maximum power drawn. I bought an Ikea one (made by whirlpool) on sale two years ago for $220 and it's rated 7.2 kW, but the instructions say you can choose max power drawn at 2.5, 4, 6 or 7.2kw. I set mine to 2.5 kw and it’s been fine so far.

  • LW2 on 14/12/2023 - 16:24

    Hey crungle/ TIA,

    I'm currently in the same boat at the moment and wanted to know how you're going with the above. Are you having any issues with normal cooking sessions, regrets or observations?

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