Preheaters warm your sap before it enters your evaporator pan. This helps you maintain a strong boil and increases efficiency. Preheaters can come in many shapes and sizes. Two examples are the Smoky Lake Feed Pan or Preheater for a Hood.
Many maple producers have tried preheating their sap by coiling their sap inlet pipe around their stack pipe. The draw backs of this method are scorched sap, air locks, or trapped steam.
The Smoky Lake Preheaters which are used within evaporator hoods use steam to heat the sap within a series of tubes before it enters the evaporator pan. A special drip tray is affixed beneath the tubes which allows steam to pass through it but prevents condensation from dripping back into the evaporator pan. The condensation is then drained from the system through gutters inside the hood.