No, you don’t need to train Sense. Sense is able to identify many common appliances (refrigerators, washing machines, etc.) on its own. Some device signatures may be recognized as a heat, motor, or mystery device, and you can help train Sense by renaming devices once they are detected. This kind of crowdsourced data is helping Sense's device detection capabilities and accuracy grow exponentially as more monitors come online, so your work helps the whole community!