Econoburn EBW-100 fan control

[MikeeH]

I am finishing up the installation of my Econoburn 100 and have a question about fan control and overheat protection. What I understand from the manual is the fan is either on or off depending on temperature below or above the desired setpoint. So why do we need a separate aquastat to shut off the fan if temperature gets to 210? Shouldn't the fan already be off at that point?

 

[pybyr]

My understanding is that it is for safety reasons-- both so that there is a second control as a fail-safe, and because the mechanical aquastat is specifically rated for such safety-type duty to interrupt a runaway system, whereas the digital controller is not.