Hello. This writing will explain more in depth on how it works.
http://en.wikipedia.org/wiki/PID_controller The i723 is a true three-term PID controller. I must admit, it is impressive to watch the i723 actually work. When first starting the i723, the draft motor ramps up to a maximum speed, creating a hot burn in the firebox (keeping the creosote forever away) , then as the temperature of the water starts rising and approaching the set point (150F and user adjustable with simple up & down button) the draft motor starts slowing down so that it reaches the set point (150) as quickly as possible, but without exceeding the set point. It makes a calculated prediction from recent past history in time, how long it is taking at a given draft blower speed to elevate the water temperature from some temperature to some higher temperature. Same type of calculations are performed on time needed for water temperature to lower.... This is how it works and is able to keep a tight window around the set point temperature and within the capacity of thermal recovery of the stove (providing there is fuel for the fire), maintain this set point temperature even as various home heating loads are imposed.
Picture of i723 out of the enclosure.
http://www.burnrite.net/images/product_002.jpg There are two 32 MHZ microcontrollers on the back side of the assembly which talk to one another using a protocol, they are optically isolated for safety from the AC voltages while performing the calculations and PID math, gathering temperature and providing information to users via the LCD display, checking for errors and safety function calls to shut the OWB down in the event of disconnected temperature sensor or over temperature. There is a system imposed whereas if the OWB is calling for heat and over time, the actual temperature begins to degrade from set point, it is assumed that the system is out of fuel and will stop the draft blower motor and close the solenoid valve, while displaying a message on the display of that affect. Rebuild your fire, press the button and your off again!
It is USB enabled for use with specific software as an option. The i723 will operate completely unassisted/stand alone.