I have used another convention oven for many years. This new Frigidaire is disappointing in that it has no lower element, only an upper element. Manual directs to place racks at positions 1 and 4 for convection baking. After preheating, my experience is that the internal oven temperature can drop from 10 to 30 degrees when the door is opened to insert baking sheets. That initiates the upper element to return to set baking temperature and results in over heating to almost a broil to the tray at position 4. Fan appears to be working correctly. In my prior oven (same size) which had upper and lower elements, 3 baking sheets could be used in convection baking.