Yeah that's how I got mine set too. The probe on the cool side but I have to set the cool side to 84F for it comes on enough to actually create a hot spot haha. You probably need one size up. This was my first RHP. I've learned since then that if I do use another one, I'll be sure to order one size up. Better to have too much and not need it than too little and need it. That's why I like the flexwatt, it's pretty much just one wattage per say so I just turn it up by about 5F during the winter.