Quote Originally Posted by southbay54 View Post
mine will it just comes on and off a lot

I strictly just used my flex tho
The only time you can plug more than one heat source into a single thermostat is when they are all identical in every way. If the wattage of the heat sources, or the type of heat sources is different you cannot use both, this goes against the basic function of a thermostat. There are thermostats like the herpstat 2 that combine more than one thermostat into a single unit, but these have multiple probes, separate outputs, and separate set points.