I have a OWB Wood Master 440. After reading a post a few weeks ago and now I can't find it. They were talking about the difference when the fan would come on and shut off. Never messed with it so I thought I would take a look and see. It only had a 5 degree range. I adjusted my aqua stat for a range of 20 degrees. So my question is why would they have it at small amount when even house boiler have a range of 20 degrees?