Final answer:
A refrigerator is a heat pump that removes heat from the cold reservoir and discards it to the hot reservoir. According to EPA regulations, a person opening an appliance for maintenance, service, or repair must have a self-contained recovery machine, unless they are working on appliances that meet certain criteria.
Step-by-step explanation:
A refrigerator is a heat pump that removes heat from the cold reservoir and discards it to the hot reservoir, while work is done on the working substance. The purpose of a refrigerator is to cool the space inside it by removing thermal energy. Therefore, a refrigerator is considered a heat engine operated backward.
According to EPA regulations, any person who opens an appliance for maintenance, service, or repair must have at least one self-contained recovery machine available at their place of business. However, there are exceptions to this rule. Appliance repairers are not required to have a recovery machine if they are working on appliances that do not contain refrigerants, appliances that are not in use, appliances that are not repairable, or appliances that are not owned by the person.