what setting are you using? or what % 0-99
I guess it depends on how warm your stove is, usually after a while if it's not burning too hot, it just blows cooler air. Everyone has their own personal favorites on the stove and settings with the coaltrol
I use the FEED (when you first start your stove) to get it burning hotter faster, it FEEDS it for 10mins and then i turn the ManFan up to like 40-50 or so, and let it run for while to heat up faster.