I replaced my six, 120V heaters in the two greenhouses with two, 240V heaters. I have two 120V heaters on a separate circuit (and remotely thermostated) just in case I should lose a primary heater. The new 240V heaters really put out the heat and have strong fans, but they are internally thermostated. Internal thermostats are pitiful, and though these are pretty expensive heaters, I just don't like their accuracy. I have now purchased two 240V thermostats to be hard-wired to the heaters and the electrician is installing those thermostats today. The heaters will then turn on/off within 2 degrees F. I will sleep better at night knowing the heat will be accurately controlled.