I have line volt thermostats for each of the baseboard heaters in my
condo. The thermostats are old analog and ugly. I want to replace
them with electronic thermostats. I pulled one of the old thermostats
off the wall to check the wiring. A single pole should have 2 wires,
while a double pole has four. My thermostats have 3 wires plus a
ground. One red, one black and one white. On the electrical panel,
there are 2 breakers for the heat, so I'm assuming it's 240 volts to
the heaters. I've looked for hours on the web, and I can't find an
example wiring diagram that matches what I have. Any ideas or
suggestions? The mini wiring diagram on the old thermostat shows it to
be a single pole with one wire to line and one to load. No mention of
the third wire at all, making it rather useless.

Thanks in advance!