Where do you measure the temperature when checking furnace temperature rise?

The rise in Air temperature is the difference between heated supply of air from the furnace and temperature of the return.

Explanation:

The temperature of the furnace should be kept within the plates range. Temperature rise of the furnace should be measured while the installation. The outside air temperature of the furnace is easy to measure whereas inside temperature is more difficult to measure. An excessive temperature rise in the furnace could cause combustion problem.