The phrase refers to troubleshooting thermal issues or energy standards for Bosch refrigeration appliances . "EN 153" is a European technical standard used to measure the energy consumption and volume of household refrigerators and freezers. When an older Bosch unit (such as the Bosch EN153 freezer ) is described as "hot," it often indicates a mechanical failure or a need for maintenance to maintain efficiency. Understanding Bosch and the EN 153 Standard