How to test a thermal overload relay? Thermal models use a bimetal strip that bends under heat. Press the built-in test button if available to simulate excess current. Here, we outline the different ways to do so. Regular testing is crucial to ensure it will perform its life-saving function when an. Learn how to test a refrigerator relay and overload protector step by step. The main purpose of this post is to discuss the testing procedure of my today's device.