Gas Heat ESCO Practice Exam

Fan time/ Temperature delay switches are used on gas furnaces to:

1. allow the fan to come on immediately.

2. allow the heat exchanger to cool down.

3. allow the heat exchanger to warm up.

4. regulate the thermostat settings.

The correct answer is: allow the heat exchanger to warm up.

Fan time/temperature delay switches serve a specific function in gas furnaces related to optimizing performance and protecting the equipment. The correct answer is related to the process where the heat exchanger needs a certain period to reach an appropriate temperature before the fan activates to circulate warm air throughout the space. When the furnace operates, it heats up the heat exchanger, which then transfers heat to the air. If the fan were to come on immediately while the heat exchanger is still cold, it would circulate cooler air, making the heating system inefficient and uncomfortable. Thus, the delay switch ensures that the heat exchanger warms up sufficiently before the fan starts, allowing for the circulation of warm air only after the desired temperature is reached. This not only improves comfort in the home but also enhances the efficiency of the heating system and prevents potential damage to components through excessive cycling. The other options do not accurately describe the function of the delay switch because they either misrepresent the timing of fan operation or relate to aspects like thermostat settings, which are separate from the temperature management of the heat exchanger itself.