The idea was to put breeding snakes in one rack and non breeding snakes in another. When cooling time comes, I separate them to different thermostats and normally can plug them into one. Of course, you may ask, if you need two sets anyway for cooling, why not just adjust the temps on the second t-stat? I am thinking ahead when I have more and more racks, then I can just plug all cooling snakes into one set, non-cooling snakes into the other set etc.