You are not asking me, Lucky, but I used Sure STAT Weatherproof Thermostats. My first pair were plug-in types, used with 110V heaters. These were the Model T1120P. When I switched to 220V heaters, the thermostats had to be hard-wired (I had an electrician do this), and these two were the Model T110. I purchased my thermostats from Northern Tool & Equipment.
I always position my thermostats 1' off the ground and about 8' from the heaters. This allows the thermostats to be minimally influenced by the (direct) heat produced when the heater is on. You want the thermostat to be positioned in an area that you believe would be the coolest in the greenhouse. At least that was my thought process when installing them.
