If your commercial oven is slow to preheat or not heating to the right temperature, possible causes include:
Defective heating elements. Have an appliance technician test elements for continuity and resistance.
Failed thermal fuse or limit switch. These safety devices may need replacement if tripped.
Broken temperature sensor or probe. The oven can’t regulate temperature without accurate readings.
Damaged control board. Control boards manage oven functions and may need replacing if faulty.
Poor airflow and ventilation. Ensure vents aren’t clogged so heat can circulate properly.