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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D'>Dear Jock<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Only taking up one issue:<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><div><p class=MsoNormal><span style='color:#1F497D'>></span>Further, reducing the secondary air increases the heat in system and increases the pull on the primary air = faster pyrolysis. But it also reduces the turbulence promoted by vigorous secondary air.<span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>The turbulence is a consequence of the shape and orientation of the incoming air ducting. You can’t get a good system working and then drop the secondary air without compensating for the mixing issues and the primary air flow, as you pointed out. The increase in temperature (from the drop in excess air) increases immediately the heat transfer efficiency and reduces CO and PM (until the ‘bottom is reached’).<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>If the draft is strong, you need only a tiny amount of primary air. To burn clean you have to decrease the EA as much as possible. For biomass you should be looking in the 70-100% range for a small stove (O2 in the exhaust @ 8-10%).<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Crispin<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p></div></div></body></html>