A heating apparatus for a heat exchanger system includes a manifold having a plurality of burners, a shutoff valve, a first controller and a second controller. The shutoff valve divides the manifold into a first manifold portion and a second manifold portion. The first controller selectively controls the communication of a fluid within the manifold. The second controller selectively actuates the shutoff valve between a first position and a second position to control a firing rate of the plurality of burners.