Running two induction units (1800 W, 120 V, 15 A each) on top of GE electric coil element stove through the stove cable and 50 A 2-pole breaker

Question

I have placed two induction surface units on top of our 30-year-old GE coil element stove (model JSP31GOP1WH). I have removed all four coil burners. Each of the induction units is rated at 1800 W at 120 V so each draws 15 A. The instructions for each unit states to plug into a 20 A circuit, but we have only one 20 A circuit available. Right now we have both connected to that circuit through a 20 A GFCI duplex receptacle. We only turn on one unit at a time.

Obviously I could install another 120 V 20 circuit, but I would like to get power through the heavy 4-wire aluminum cable (original 53 year-old 50 A GE breaker) that the stove appliance cord connects to through a NEMA 14-50 receptacle behind the stove.

My first thought is to connect a 12 or 10 AWG cable (3 + gnd) to the connection block on the back of the stove where the cord connects. I would route this behind the stove to a box surface mounted on the top back of the stove (magnetic hold fast?) or just resting there. This would be a multiwire branch circuit sharing a neutral or two separate neutrals wired to a 20 A duplex receptacle.

Another thought is to snake the 12 AWG cable through the back of the stove into the 3 inch high space under the stove top but I have pretty much rejected that.

The oven of the this stove still works and we are reluctant to buy a new induction range if this cheaper solution would work.

EDIT

The suggestion in one answer or comments is to install a subpanel to obtain both 240 V and 120 V power from a 6-6-6-6 aluminum cable fed by a 50 A breaker in the main panel currently going to a NEMA 14-50R.

The purpose of this would be to get two 120 V 20 A circuits to operate the two countertop induction cooktops sitting on top of our 30-year-old GE electric range. I have removed all four coil elements to prevent damage if a coil were accidently turned on. Currently both induction cooktops (each rated at 1800 W so 15 A at 120 V are plugged into one dedicated 20 A circuit. I cannot use both at high power. One unit is a 2-burner and one is a 1-burner but each is rated at 1800 W total. The 2-burner will allow all 1800 W on one burner, but will divide power if both burners are on to keep the total power at 1800 W or less.

I want to keep the 240 V power to the NEMA 14-50R because the GE range is plugged into that and the oven of the GE range is working perfectly. It is not a forced air oven, but an old fashioned "still" oven, but we find it OK. I have a sentimental attachment to this oven because a now deceased friend was instrumental in getting the faulty oven timer/control unit repaired since a new one was not available.

I would install the subpanel in the wall of the room the kitchen stove backs on and would put a picture over the subpanel. I want to bring existing 6-6-6-6 aluminum cable into the subpanel and take 6-6-6-6 copper from the subpanel into the box for the NEMA 14-50R so I can use the highly rated Bryant NEMA 14-50R which requires copper conductor.

The subpanel would have two 20 A 1-pole breakers for two separate 120 V circuits for the two separate induction cooktops. Should the subpanel also have a 2-pole breaker (40 A minimum per intructions for GE range) for the 6-6-6-6 copper to the 14-50R or can I just connect through lugs?

Answer 1

Might as well stop paying for your insurance coverage, they will laugh all the way to the bank when that turns up if you need to make a claim.

You potentially COULD do this in a legit fashion by installing a 50A sub-panel, if you can provide working space for a sub-panel.

Connecting 15A devices or 12 AWG wires to a 50A breaker without a sub-panel and 15 or 20A breakers FIRST - no way. Having watched my oven element turn to incandescent slag while the stove's breaker went "ho, hum, not more than 50A" I can affirm that it would be a rather severe fire hazard.

Answer 2

Since the range is scrap anyway, I would hack the range.

They make dialects of Eaton, Square D and Siemens breakers that have mounting screws on their face and are meant for face-of-enclosure installation. Modify the range so instead of the four heat level knobs, those are now breakers. One 15-20A 2-pole breaker for the oven, and then 2-3 more 20A breakers feeding 2-3 120v receptacles mounted on the back of the range. Notice how common 120V receptacles are designed for face mounting on equipment simply by drilling and nibbling two oval holes and three screw holes; or alternately nibbling a big rectangular opening for Decora and two screw holes.

Rockwool insulation and plenty of it to keep the oven's heat away from the equipment. Use high-temp wire (finding that would be the trick; try GALCO, Grainger or McMaster-Carr). Then do something cosmetic to blank over the entire cooktop. Alternately, you could get induction units intended for installation into a surface and install them.

Make sure you have an honest 4-wire connection because running a contraption like this 3-wire would be a recipe for fatality.

This advice is 100% NEC legal (can't say the same for UL) because NEC doesn't regulate appliances; UL does. UL would probably treat it as "A PDU/power strip with a built-in oven" for White Book compliance.