Which of the following is NOT a common refrigerant used in boilers?

Freon is commonly associated with refrigeration systems and is a type of refrigerant used primarily in air conditioning applications. When considering common refrigerants used in boilers, it is important to recognize that traditional refrigerants like Freon are not utilized in boiler systems for their heating functionalities. Instead, boilers typically use substances that can transfer heat through boiling and condensing processes, like water or steam, and refrigerants that are more suited for heat exchange, such as ammonia and lithium bromide.

Ammonia is often used in industrial refrigeration, while lithium bromide is commonly used in absorption chillers, often in combination with water. In contrast, lithium chloride serves a similar function but is less common than the other two.

Thus, while Freon may be widely recognized in the refrigeration field, it does not play a role in boiler systems, making it the option that is not typically considered a common refrigerant within that context.