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EDIT 3: Going to end up going with Harper and crip659 on this one. I honestly was worried that there was a justification to have this set up in the way that it currently is, but seeing as no one seems to be able to justify such a bizarre design choice I'm going to just remove the receptacle and the sub panel as it's the safest thing to do. Thanks to everyone who contributed! EDIT 2: More updates, this time to the graph + added details on cooktop. EDIT: Adding details, updating diagram + adding pictures.

Looking for some advice on a little situation I have going on in the kitchen. We've recently had to upgrade our cooktop as the old one had several elements that had just stopped working.

The situation: The cooktop is wired to a 40amp breaker in the main panel which terminates as a 240 volt outlet in the kitchen and that outlet actually has a subpanel plugged into it (AWG of plug is 2AWG) that then connects to the cooktop(cooktop's wires are 8AWG). The part I'm confused about is that the subpanel has two single pole 20 amp breakers (one for the red led and one for the black led) but everything I look up is leading me to believe this appliance should be on a 40amp breaker. Why would someone wire it in this way? I need to replace one of the breakers as I misplaced it when changing them out, so I want to know if I should just buy a 40 amp breaker or stick with how it was originally installed.

Additional Details:
Subpanel: Square D QO Load Center Cat.QO 6-12 T Series L4 (rated for 100 Amps max, 120/240 v I PH. 3W.
Old cooktop: 240v - 8.1kw.
New cooktop: 240v - 7.8kw AWG of wire running from the plug to the subpanel - 2AWG AWG of wire running from cooktop - 8AWG

Cooktop Info FORNEBO (IKEA) Induction Cooktop with downdraft ventilation https://www.ikea.com/ca/en/p/foernebo-induction-cooktop-int-extractor-70537757/ Voltage: 240/208V Connection rating: 7400W Current: 32A

Diagram Diagram

][2]

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  • 1
    where is the subpanel located? does it have permanent 30in clearance in front of it? if not then you are in violation of code Jul 25, 2023 at 21:06
  • 3
    I am not sure if a sub panel can be plugged in, but I doubt it. The breaker size in the sub panel will depend on what the stove's instructions say. It might be cheaper and easier to plug the stove in, than maybe having to rewire(remove the plug) the sub panel. Not enough info right now.
    – crip659
    Jul 25, 2023 at 21:06
  • 1
    What size wire goes to the plug?, to the sub panel? and to the cook top?
    – JACK
    Jul 25, 2023 at 21:15
  • 3
    You need to go by the the instructions. All sub panels I have seen/read about are all direct wire to the main panel. It is usually better to limit the number of different connections, so needing the stove to be hardwired, it would nicer/better if the plug and sub panel was not needed, just use the box the plug is in as a junction box(if it is big enough).
    – crip659
    Jul 25, 2023 at 22:11
  • 1
    @JimStewart I forgot to mention I had made a mistake with my original diagram, the 240 volt plug actually has four prongs, not three (three flat prongs and one rounded one for the ground).
    – Litmus99
    Jul 25, 2023 at 22:38

1 Answer 1

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You must follow instructions and labeling

... when installing electrical equipment. It was entirely improper for the last guy to "freestyle" the subpanel, individual breakers, and wrong size of breaker.

I guarantee you the instructions and labeling are calling out a 40A breaker.

So the subpanel should be removed altogether, and simply plug the cooktop into that in-wall socket.

If there is a need to power both a cooktop and an oven from that circuit, ask a question about that - there are ways to power oven+range on the same circuit.

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  • But could the instructions state to hard wire it and make no reference to a receptacle that a cord with plug goes into? If there is a NEMA14-50R in the wall it would sure be convenient to just get a cord with a 14-50P on the end, connect that to the connection block of the cooktop, and plug it in. With an expensive new cooktop would it be prudent to use a voltmeter to verify that the receptacle is wired correctly? Jul 26, 2023 at 0:53
  • 1
    @Jim then get rid of the receptacle and hard-wire it. Jul 26, 2023 at 1:12
  • Would you have to put a box extender on the box with the NEMA 14-50R to make room for a hardwired connection? Jul 26, 2023 at 15:25
  • @Jim don't know, you'd have to look at the cubic inches of the box that was there. But it'd be easy enough if needed. Jul 26, 2023 at 17:32
  • 1
    Funnily enough, I did just that as the wires felt really cramped in the box and I could only find 4 11/16 blank junction box covers (ideally I would have needed one with a knock-out as the box is embedded in the wall).
    – Litmus99
    Jul 27, 2023 at 2:08

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