[mijero]

I have a 40 amp dedicated circuit for a cook top wired with 8-3 wire containing four wires, white, black, red and copper. The cook top I purchased has three wires, black, red and copper. Why doesen't the cook top have a white (netural) wire? And what do I do with the white wire?

[stanfortyman]

The cook top I purchased has three wires, black, red and copper. Why doesen't the cook top have a white (netural) wire?

Because it does not need or use one. That would be a straight 240v appliance, where one like it that requires a neutral would be a 120/240v appliance.

And what do I do with the white wire?

Just cap it off.

[abcsalem]

FYI,
120v appliance requires, one HOT, one Neutral, one Ground
240v appliance requires, two HOT (from a dual pole breaker) and one Ground
120v/240v appliance requires, two HOT (from a dual pole breaker), one Neutral, and one Ground

[ZoeMarie]

I asked the same question on here when we got our cooktop. Stanfortyman is right. We capped off the white and we were good to go