I have a situation very similar to using two oven in one outlet. I'd like to install a 30 amp GE Advantium 220v oven and a 20 amp GE thermal oven on an existing circuit with a 50 amp breaker. However, both installation manuals ask for dedicated circuits. Quoting the Advantium manual here: "Power should be supplied from a separate, dedicated 30-ampere branch circuit."

Ordinarily I'm a follow-the-instructions kind of guy, but I did notice that the manual used the word "should" in this sentence rather than the "must"s which were liberally sprinkled elsewhere. Pulling a new circuit is possible but a lot of work. I'd appreciate feedback from experienced DIYers or electricians. If I follow my instincts and install both ovens to the existing junction box with the existing 50 amp circuit, what risks am I taking?

  • They likely say "should" because they are concerned that some components might be damaged if fed from a larger shared breaker. In your situation even though the total adds up to 50A, if something starts to go wrong in the 20A unit, nothing is going to react to it until it is pulling 50A+, and by then you may have a fire happening. They are doing "CYA". Just because you can, doesn't mean you should... – JRaef Sep 17 '19 at 22:34
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    Can you provide a picture of the junction box? Is there room for a small sub panel? – JACK Sep 17 '19 at 22:47
  • Thanks JRaef. JACK, I don't have a picture handy, but adding a subpanel inside the cabinet is definitely not to code, and outside the cabinet would be pretty ugly. – Martin Sep 19 '19 at 1:23

You can normally connect 2 ovens on 1 breaker per the NEC but the manufacturer instructions over ride the NEC per 110.4.B , listed or labeled equipment shall be installed in accordance with any instructions included in the listing or labeling. This means you have to follow the manufacturers instructions. I agree with @JReaf that the control cycling of the elements in one oven may damage the controls in the second oven. We see this in industrial plants all the time and put spike suppressors (MOV’s or diodes on relays depends on if ac or dc) control. But with the mfg instructions stating they need to be on separate breakers a code compliant install requires 2.

  • 110.3B. But yes, this answer is it. OP's only possible out is the "should" where "must" would be... – Harper - Reinstate Monica Sep 17 '19 at 23:10
  • I would call that an instruction, I did read the cut sheet to see if the op may have missed the wording. That’s why I included the entire sentence. – Ed Beal Sep 17 '19 at 23:17
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    @Ed Beal Would a 20 amp and a 30 amp circuit from a sub panel fed from a 50 amp breaker be considered dedicated circuits? – JACK Sep 18 '19 at 0:54
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    Yes they would that’s why if the name plates comply to the NEC “tap rules” I look no further. If it says max breaker size that is LAW. Like I said the instructions need to be followed. But the name plate is all that inspectors check unless the are different from the code. Good question + note the total can be more than 50 because the testing proves no one uses all the burners , elements for 3 hours and that is part of the protection built into the code. – Ed Beal Sep 18 '19 at 1:15
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    Thanks Ed! I will run a new 20A circuit for the wall oven, and change out the breaker on the 50A circuit to 30A for the speed oven. – Martin Sep 19 '19 at 1:30

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