ok, few electical questions.

First I'll briefly explain what I'm trying to do.
Hooking up a thermostat for infloor heating in kitchen, existing house, not
new.
So we are installing a new Range to replace the stovetop that was there from
previous owner, we ran a new wire for the new range. We are now using the
existing wire (from stovetop) for the hookup of the infloor heating witch is
a 240v line which is required for the infloor heating. Now the problem.

This a 3wire (red,black,white & ground). Now the thermostat requires 2
wires to hook up. my question, which wires do I hook up? I turned on the
breaker to see what voltage each wire has:

White 0 volts
Black 118 volts
Red 119 volts

do I just hook up the black and red wires and forget the white wire?

I know, call an electrician, but I almost got it done, this is my last
problem.

Any help would be appreciated.

Thanks,
Steve