On conventional refiners that have a high-pressure burner system, the normal method used to provide cooling is to reduce the fire pressure to zero, turn off the fuel and then use the combustion air through the same burner for cooling. This type of cooling is referred to as a dual function burner system. Its main disadvantage is that going from instant heating to instant cooling, or the reverse, causes a severe temperature cycle. The temperature cycle will not let the refiner be operated at a temperature which will require the control instruments output to be near the cross over point between heating and cooling.