Evenin all, OK, that's it...Doc, i'm gonna stick a thermometer in the bottom of one of my pots, just to see. The number you gave of 66F could be an issue for me , not sure. I have them on large plant trollies , that sit about 2,1/2" off the painted concrete floor. I've never addressed this issue before,....perhaps i should start. Thanks for the info Doc. and Capn!