When your chimney fan will come on is a guess if you don't know the temp setting for the snap disc. I have two on my rig one set at 150* on the boiler tube to supply electrical power (so that the fans will only run when the frig is on) and the other set at 90* in the upper chimney to turn the fans on (I have two). With temps @ 100+ outside in the desert my frig has stayed cold. I put my battery operated cool can fan on the bottom shelf to take advantage of the colder air there and blow it upward I also make sure there is space between the items in the frig to ensure proper circulation of air. good luck.