In accordance with patent approval, calculations were performed by computer model of this boiler under typical conditions. It was determined that the design improves the efficiency of the boiler by as much as three to five percent, relative to other boilers having traditional designs. In other words, this new internal, integrated design performs the function of an economizer typically used with conventional steam generation systems, to capture the lost or waste heat from the hot flue and stack gasses of the boiler. In conventional boiler designs, the economizer is a device that has separate housing and ductworks, in addition to the boiler housing, providing a bulky assembly. In contrast, these new Hurst designs give the user an opportunity to save on economizer housings, ductwork and on overall boiler room expenses.