Quote Originally Posted by blueapplepaste View Post
I'm going to set the ranco a couple of degrees warmer and put its probe on a different level, and then plug the herpstat into the ranco. This way if I had what happened here happen, the ranco would have turned off the herpstat and shut down the power.
Yes, but that way, if either the Ranco or the Herpstat fails, your rack won't be heated at all -- not really a "backup" as much as a kill-switch. The question becomes whether the risk of a probe being jostled loose is greater than that of a thermostat failing, because either setup incurs risk.