I have a older GE cook top I would like to replace. The wiring has a red, black and white. The new cooktop has black, red and a bare copper wire. The instructions state that the appliance is a 240 volt unit and to connect to a 3 wire 120/240 volt power supply. The neutral, I assume white, is not required. The cook top is grounded to the frame and should be grounded separately.

So I should hook the red and black and nothing to the white? And where do I find the separate ground? Can I use the white wire fro a ground?

You can use the white as a ground, but first you need to see if the white is connected to a neutral bar in a main panel that has a main breaker in it.If so, then nothing else needs to be done.

But if you have a panel without a main breaker, there should be inside a neutral bar AND an equipment ground bar. The white will need to be disconnected from the neutral bar and transferred to the equipment ground bar, so the white could be used as a ground for the cooktop.

I have a older GE cook top I would like to replace. The wiring has a red, black and white. The new cooktop has black, red and a bare copper wire. The instructions state that the appliance is a 240 volt unit and to connect to a 3 wire 120/240 volt power supply. The neutral, I assume white, is not required. The cook top is grounded to the frame and should be grounded separately.

So I should hook the red and black and nothing to the white? And where do I find the separate ground? Can I use the white wire fro a ground?
The breaker panel has a main switch. I pulled the cover to the breaker panel, and there is a bunch of wires that are white that got to the neutral bar. How can I tell for sure which wire I am looking for?

You can use the white as a ground, but first you need to see if the white is connected to a neutral bar in a main panel that has a main breaker in it.If so, then nothing else needs to be done.

But if you have a panel without a main breaker, there should be inside a neutral bar AND an equipment ground bar. The white will need to be disconnected from the neutral bar and transfered to the equipment ground bar, so the white could be used as a ground for the cooktop.

Breaker box has a main switch. There are many white wires going to the neutral bar. How can I tell which wire to check for?

You need to find the white that goes out in the same cable as the red and black going out to the cooktop. You may want to shut off the main so you can rummage around in the panel with you fingers to find this cable and wires. Keep in mind, the large wires feeding the Main breaker are still very live, with the Main breaker Off.