Final answer:
The blower fan in a combination limit control typically turns off at about 130°F to prevent the system from circulating air that is too cold or overheating.
Step-by-step explanation:
The combination limit control is a device used in heating systems to regulate the operation of the blower fan based on the temperature of the system. While the exact temperature at which the blower fan turns off can vary depending on the specific limit control settings and the design of the HVAC system, the options provided (100°F, 200°F, 130°F, and 127°F) are common set points for different systems.
However, based on common practices and safety considerations in HVAC systems, a typical setting for a blower to turn off in a residential system is often around 130°F. This temperature ensures that the blower fan does not circulate air that is too cold, which could lead to discomfort and inefficiencies, nor does it allow the system to overheat, which could be dangerous.