Red to red, black to black (although it really doesn't matter if you reverse them), and green to the bare ground. Cap the white with a wire nut and fold it back in the box, it's not needed in this situation. The cooktop is straight 240v while the house wiring can accommodate a 240/120 appliance.

I'm assuming the circuit you're connecting to is appropriately sized for the cooktop.

Cooktops I don't know about, but ranges and wall ovens typically have a 120V lightbulb inside (and some older ones had 120V convenience receptacles as well).

"We've got a lot of older grandfathered 3-wire installations, but code now wants 4-wire receptacles, with ground/neutral seperate. "

This only applies to 120/240v appliances. The OP has a straight 240v appliance. The neutral is not needed but a ground is.

Mike - thanks for the confirmation. That's what I thought was meant but I feel better with some validation. Appreciate the response.

"Cooktops I don't know about, but ranges and wall ovens typically have a 120V lightbulb inside (and some older ones had 120V convenience receptacles as well)."

The manufacturers (probably at UL prodding) finally did away with the 'convenience receptacles' during the 1970s.
The stove did not have any secondary overload protection, meaning there was a 30-50 amp breaker feeding that receptacle.

The oven I want to buy is a 120/240v wall oven, and the spec says 20A circuit. If it's a 3wire connection, would a 10/3 wire cause damage when used in a 2-pole 20 breaker?

My cooktop is a 120/240v surface mount, 40A and it has only two wires (black/red) and a bonding ground. Wouldn't that make it an 8/2 conductor for this circuit?

About the oven then, if the oven has (I don't know yet) the same wiring (red/black/gnd), then could a 10/2 be used if it's a 20A circuit?

I hope this response goes to my email. ;)

ksvalentine, it would have been better to start a new thread for your questions instead of adding them to this existing and still active thread.

The responses will not go to your e-mail. I don;t think this site offers this function. I hope you come back to check.

Both your new appliances will need FOUR wires. Two hots, a white neutral and a green or bare ground. If the appliance only has a black and red it will be a 240v appliance, not a 120/240v appliance.

peter racer-

Thanx, this is my first time on this blog. I posted a new thread.

"The oven I want to buy is a 120/240v wall oven, and the spec says 20A circuit. If it's a 3wire connection, would a 10/3 wire cause damage when used in a 2-pole 20 breaker? "

No, 10 ga. is fine. A 20A is allowed to be as small as 12 ga. (provided that it doesn't have to be derated for some reason). You can always under-breaker a circuit, as long as whatever is feeding the circuit will run without tripping.

The manufacturers (probably at UL prodding) finally did away with the 'convenience receptacles' during the 1970s.
The stove did not have any secondary overload protection, meaning there was a 30-50 amp breaker feeding that receptacle.

I've seen at least one with one of those pushbutton thermal breakers (like you find in the back of old TVs) for the receptacle.