posted on
February 18, 2010 at 09:22AM
It will most likely be a 220 -240v, 50A circuit. Dryers are usually 30A, and smaller cooktops COULD be 30A.
Modern cooktops will come with red, black, white, and green/bare wires.
Red - Hot 120v, Black - Hot 120v, White - Neutral, Green/Bare - Ground
I often frown upon hardwiring, as it does not allow for a "means of disconnect" for the power supply, other than the electric panel. With a cooktop, versus a range, you could have access to a cord and plug via a cabinet door, but, again, this is determined by local code.
I also frown on old three wire installs, Red, Black, and Green/Bare, as they require bonding jumpers, and leave no separate path for ground, and neutral. If the bonding jumper should fail, it leaves the potential for the appliance chassis to become energized. You should not tie the white, and bare/green together, as this is a potential safety hazard. It used to be permissible by code, but, that "grandfathering" was addressed, and changed to being a "no-no".
The best thing you can do is pull a new four wire circuit for your modern cooktop. More expensive, yes. Safer, HELL YES.