The key to efficient and clean wood burning is a long turbulent flame path that does not cool until the burn is complete. A lack of oxygen during this process will cause an incomplete burn and sooting or creosote buildup. Excessive air will lower the combustion temperature and reduce the heat transfer. Water content can also lower the efficiency, because it takes energy to evaporate the water.
  The Seton boiler has a reversing flame path over three long with a balanced draft and a 99% combustion efficiency.
  Once the wood is burned cleanly the heat transfer to the water can start. To attain the highest transfer efficiency, it is important for the gasses to exit next to the cold return water and the transfer surfaces to remain clean.
  The Seton Boiler design does this, it combines a self cleaning water tube pressure vessel with a down draft exhaust.
  The Seton boiler has an exhaust temperature below 400° and maintains thermal transfer efficiencies of 80 to 85%.
  This boiler does not need water storage to operate efficiently. This is the only wood boiler design that will turn the fire off and hold the wood until it is needed.
   The combustion process in the Seton design is more pyrolisation than gasification. After fresh wood is loaded into the combustion chamber and the first cycle is complete, the draft closes and the heat from the refractory dries the wood without air and turns the wood into coke.