4 wire to 3 wire 240v adapter cable?

I need a 240v 20 amp outlet for an induction cooktop.
I've already got 50' of 4-wire 10-gauge cable as my original plan called for a simple/standard 4 prong dyer outlet.
Is it OK to just install the 30 amp 4-wire dryer outlet and build an "adapter cord" to power the induction cooker?

My thinking is a 3-wire cable (hot hot ground) with the necessary 20amp 240v receptacle on one end, and then wire 3 of the 4 prongs of a dryer plug. The H-H-G prongs would be wired and the neutral prong would not, essentially just leaving the neutral isolated/unused in the dryer outlet.

Would this be ok?

I can go out and buy some 3-wire cable if necessary, I just thought it would be nice to use the cable I already have. Not to mention having the 30 amp 4 prong outlet already installed would be nice for flexibility down the road.

thanks for any help

Assuming you did this correctly you would basically just drop the ability to use 120 Volt power. If you do not have your neutral you can not get 120 Volts in a safe method at the plug end. This may be OK if you plan to only use 240 Volts from it.

I do not follow your question amperage wise, just take a look at some of the online wire gauge guides to sort this out, there are quite a few out there.

Hope this helps

the plug on the cooktop is a NEMA 6-20 so I don't need the 120 service, right?

DustBow said:

the plug on the cooktop is a NEMA 6-20 so I don't need the 120 service, right?

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If that's all your running, you are right. For size wire: Find a amp/wire gauge chart and see. It's not only the amp but the distance.

I am not sure how your cook top operates.

If it only uses 240V you will be OK as long as the wires are connected correctly to each plug.

DustBow said:

My thinking is a 3-wire cable (hot hot ground) with the necessary 20amp 240v receptacle on one end, and then wire 3 of the 4 prongs of a dryer plug. The H-H-G prongs would be wired and the neutral prong would not, essentially just leaving the neutral isolated/unused in the dryer outlet.

Would this be ok?

Click to expand...

Yeah, based on your indication the range top is 6-20.

Not sure about the cable...if it's meant for installed wiring, like "Romex", it may not be approved/listed for use as an extension cord.