According to Tony Hwang :
gerryincanada wrote:

I have just recently installed wiring for a 250v construction heater
and want to put a thermostat on it.

Can anyone tell me what I need to do, and can I use an old furnace
thermostat to run it?

Oh, no. You need a line voltage thermostat with 250V rating. Something
like used on baseboard heaters. Check the Honeywell web site.

Any hardware or DIY box store will have lots of choices. They're cheap.
Typically $15.

Construction heaters usually have thermostats on them, but they're not
very accurate/settable.

I have two 4800W cube heaters for heating up my garage in the winter. "Proper"
thermostats would be nice in order to set a specific air temp, but I've found
that the built-in ones are good enough to avoid getting off my butt and
spend a few bucks to install "real" ones.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.