What temperature must a thermostatic control reach before it can delay turning off the blower?

The correct temperature that a thermostatic control must reach before it can delay turning off the blower is 90°F. This temperature is significant because it is typically set to ensure that the HVAC system operates efficiently and effectively.

When the system reaches this temperature, it indicates that the environment has warmed up appropriately, allowing the blower to continue circulating air to help maintain comfortable conditions while allowing residual heat to dissipate. Delaying the blower's shutdown at this temperature can prevent short cycling, enhance overall system performance, and ensure that the indoor environment does not experience sudden temperature shifts.

In HVAC systems, thermostatic controls are designed to balance comfort with energy efficiency, and setting a delay function at 90°F is a standard practice that promotes stable indoor conditions following heating cycles.