Always put your thermostat probe directly on or over the heat tape side! If something happens and that probe doesn't register the heat it will spike your heat tape and possibly hurt or kill your snake! Probe should always be on or directly above the heat tape. You can always turn the thermostat up to make up for heat variances. My room and tubs require my Herpstat to be at 97 degrees to get a 90 degree hot spot in my tubs.

Regards,

B