The fridge defend is a safety device that turns the cooling unit OFF when the boiler reaches an unsafe operating temperature due to a variety of reasons that are not necessarily related to improper installation. For example, operating the fridge off level causes the boiler temperature to skyrocket and weakens the boiler tubes. Norcold and Dometic have safety temp switches but they are set to trigger at very very high temperatures and the ARP turns it OFF before damage occurs. It does a variety of other things as well. Personally I would not have an absorption refrigerator without the ARP device.