or regulate by comparing with a standard or desired value control may be closed loop feedback feed forward cascade model predictive adaptive heuristic and combinations thereof the term u201c controller u201d means a device at least capable of accepting input from sensors and meters in real time or near real time and sending commands directly to burner control elements and or to local devices associated with burner control elements able to accept commands a controller may also be capable of accepting input from human operators accessing databases such as relational databases sending data to and accessing data in databases data warehouses or data marts and sending information to and accepting input from a display device readable by a human a controller may also interface with or have integrated therewith one or more software application modules and may supervise interaction between databases and one or more software application modules the phrase u201c pid controller u201d means a controller using proportional integral and derivative features in some cases the derivative mode may not be used or its influence reduced significantly so that the controller may be deemed a pi controller it will also be recognized by those of skill in the control art that there are existing variations of pi and pid controllers depending on how the discretization is performed these known and foreseeable variations of pi pid and other controllers are considered within the invention controllers useful in the systems and methods of the invention may vary in their details one pid controller useful in the invention may be expressed mathematically as in equation 1 u t kp e t 1 ti u2218 u222b e t dt td u2218 u00e8 t.