How do you calculate the temperature rise in a ventilation system?

To determine the temperature rise in a ventilation system, you need to assess the difference between the temperatures of the supply air and the return air. The correct approach is to subtract the temperature of the return air from the temperature of the supply air. This calculation provides the net gain in temperature as air is heated or cooled as it travels through the system.

When you subtract the return air temperature from the supply air temperature, you're essentially measuring how much the air has warmed up as it passes through a heating element or cooling unit. Heating or cooling systems are designed to condition the air before it enters the indoor environment, and this temperature difference is critical for evaluating the system's efficiency.

Choices that suggest adding the temperatures of the supply air and return air do not reflect the intent of measuring temperature change within the system. They do not provide any meaningful information about the actual temperature rise, which is essential for system performance assessment and energy calculations. Therefore, calculating the temperature rise through the method of subtracting return air from supply air accurately reflects how much the air temperature has increased.